The Glaucophane mineral is named after two Greek words: glaukos, which means “bluish green”; and phainesthai, which means “to appear.” Specimens can be gray, lavender blue, or bluish black. Crystals are slender, often lathlike prisms, with lengthwise striations. Twinning is common. Glaucophane can also be massive, fibrous, or granular. When iron replaces the magnesium in its structure, it is known as ferroglaucophane. Glaucophane occurs in schists formed by high-pressure metamorphism of sodium-rich sediments at low temperatures (up to 400°F/200°C) or by the introduction of sodium into the process. Glaucophane is often accompanied by jadeite, epidote, almandine, and chlorite. It is one of the minerals that are referred to as asbestos. Glaucophane and its associated minerals are known as the glaucophane metamorphic facies. The presence of these minerals indicates the range of temperatures and pressures under which metamorphism occurs.
Name: From the Greek for bluish green and to appear.
Polymorphism
& Series: Forms a series with ferroglaucophane.
Mineral Group: Amphibole (alkali) group: Fe 2+=(Fe 2+ + Mg) < 0.5; Fe 3+=(Fe 3+ + Al vi ) < 0.3; (Na + K)A < 0.5; NaB ¸ 1.34.
Distinguished from other
amphiboles by distinct blue color in hand sample. Blue pleochroism in thin
section/grain mount distinguishes from other amphiboles. Glaucophane has
length slow, riebeckite length fast. Darkest when c-axis parallel to
vibration direction of lower polarizer (blue tourmaline is darkest w/ c-axis
perpendicular to vibration direction of polarizer). There is no twinning in
glaucophane. Glaucophane also has a parallel extinction when viewed under
cross polars.
Crystal System
Monoclinic
Fracture
Brittle – conchoidal
Density
3 – 3.15
Optical Properties of Glaucophane
Color / Pleochroism
Lavender blue, blue, dark blue,
gray or black.
Distinct pleochroism: X=
colorless, pale blue, yellow; Y= lavender-blue, bluish green; Z= blue,
greenish blue, violet
Characteristic of the blueschist facies, in
former subduction zones in mountain belts; in the greenschist facies and in
eclogites that have undergone retrograde metamorphism.
Distribution
Widespread in some mountain belts. On Syra
Island, Cyclades Islands, Greece. At numerous sites in the California Coast
Ranges, as on the Tiburon Peninsula and at Vonsen Ranch, Marin Co., at
Glaucophane Ridge, Panoche Valley, San Benito Co., and near Valley Ford, Sonoma
Co.; in the Kodiak Islands, Alaska, USA. At St. Marcel, Val d’Aosta, and
Piollore (Biella), Piedmont, Italy. On Anglesey, Wales. In Japan, at Ubuzan,
Aichi Prefecture, and Otakiyama, Tokushima Prefecture.
References
Bonewitz, R. (2012). Rocks and minerals. 2nd ed. London: DK Publishing.
The name anthophyllite comes from the Latin word anthophyllum, which means “clove”—a reference to the mineral’s clove-brown to dark brown color. Specimens can also be pale green, gray, or white. Anthophyllite is usually found in columnar to fibrous masses. Single crystals are uncommon; when found, they are prismatic and usually unterminated. The iron and magnesium content in anthophyllite is variable. The mineral is called ferroanthophyllite when it is iron-rich, sodium-anthophyllite when sodium is present, and magnesioanthophyllite when magnesium is dominant. Titanium and manganese may also be present in the anthophyllite structure. Anthophyllite forms by the regional metamorphism of iron- and magnesium-rich rocks, especially silica-poor igneous rocks. It is an important component of some gneisses and crystalline schists and is found worldwide. Anthophyllite is one of several minerals referred to as asbestos.
Name: From the Latin anthophyllum, meaning clove, in allusion to the mineral’s color.
Polymorphism
& Series: Forms a series with
magnesio-anthophyllite and ferro-anthophyllite.
Mineral Group:Amphibole (Fe{Mn{Mg)
group: 0.1 Mg=(Mg + Fe 2+) 0.89; (Ca + Na)B < 1.34; Li < 1.0; Si ¸ 7.0.
Anthophyllite from Bastnäs mines, Riddarhyttan, VästmanlandAnthophyllite from New England quarry, Yealmpton, DevonAnthophyllite from Wissahickon Creek, Fairmount Park, Philadelphia, PennsylvaniaAntofillit-(Anthophyllite)-Mineral
From medium- or high-grade metamorphism, in
amphibolites, gneisses, metaquartzites, iron formations, granulites, and
schists derived from argillaceous sediments, ultrama¯c, or ma¯c igneous rocks;
a retrograde reaction product.
Distribution
From Kongsberg and Snarum, Norway. At
Schneeberg, Saxony, Germany. From Norberg, Sweden. At He·rmanov, Czech
Republic. In Greenland, from Fisken½sset. In the USA, from Chester¯eld,
Hampshire Co., Massachusetts; the Carleton talc mine, near Chester, Windsor
Co., Vermont; near Media, Delaware Co., Pennsylvania; the Day Book deposit,
near Spruce Pine, Mitchell Co., North Carolina; in California, at the Winchester
quarry, Riverside Co., and near Co®ee Creek, Carrville, Trinity Co.; in the
Copper Queen mine, Prairie Divide, Park Co., Colorado. From Munglinup, Western
Australia.
References
Bonewitz, R. (2012). Rocks and minerals. 2nd ed. London: DK Publishing.
Platinum is a precious metal that is known for its rarity, beauty, and various industrial applications. It is a chemical element with the symbol Pt and atomic number 78 on the periodic table.
Introduction: Platinum is typically found in nature as a rare mineral, but it is more commonly obtained as a byproduct of other metal mining, particularly from ores containing nickel and copper. It is a dense, malleable, and highly corrosion-resistant metal, making it valuable for various purposes, including jewelry, catalytic converters in automobiles, and industrial applications. Its name “platinum” is derived from the Spanish term “platina,” meaning “little silver,” because early Spanish explorers often encountered platinum alongside silver deposits and initially considered it a nuisance.
Definition as a Mineral: In a geological context, it is considered a mineral when it naturally occurs in the Earth’s crust. It usually forms as small, nugget-like grains or irregular grains within certain types of rocks and ore deposits. Platinum minerals are commonly associated with nickel and copper ores, and the primary mineral source for it is often the mineral sperrylite (PtAs2). Sperrylite is a platinum arsenide mineral that is one of the few naturally occurring minerals containing platinum as its primary component.
Platinum can also occur as an alloy with other elements in nature. For example, native platinum, which consists mainly of platinum (Pt) and minor impurities, is a rare occurrence. It is usually found in alluvial deposits, often associated with other heavy minerals like gold and palladium.
It’s important to note that the vast majority of the world’s platinum production comes from primary sources (ores rich in platinum-group elements), rather than from native platinum. Extracting platinum from its ores and processing it is a complex and energy-intensive industrial process. It is highly prized for its luster, durability, and resistance to tarnish, making it a valuable material in various industries and for decorative purposes.
Cell
Data: Space Group: Fm3m. a = 3.9231 Z = 4
Name: From the Spanish platina, diminutive of plata, silver.
Platinum is a precious metal that is known for its rarity, beauty, and various industrial applications. It is a chemical element with the symbol Pt and atomic number 78 on the periodic table. Here’s an introduction and definition of platinum as a mineral:
Introduction: Platinum is typically found in nature as a rare mineral, but it is more commonly obtained as a byproduct of other metal mining, particularly from ores containing nickel and copper. It is a dense, malleable, and highly corrosion-resistant metal, making it valuable for various purposes, including jewelry, catalytic converters in automobiles, and industrial applications. Its name “platinum” is derived from the Spanish term “platina,” meaning “little silver,” because early Spanish explorers often encountered platinum alongside silver deposits and initially considered it a nuisance.
Definition as a Mineral: In a geological context, platinum is considered a mineral when it naturally occurs in the Earth’s crust. It usually forms as small, nugget-like grains or irregular grains within certain types of rocks and ore deposits. Platinum minerals are commonly associated with nickel and copper ores, and the primary mineral source for platinum is often the mineral sperrylite (PtAs2). Sperrylite is a platinum arsenide mineral that is one of the few naturally occurring minerals containing platinum as its primary component.
Platinum can also occur as an alloy with other elements in nature. For example, native platinum, which consists mainly of platinum (Pt) and minor impurities, is a rare occurrence. It is usually found in alluvial deposits, often associated with other heavy minerals like gold and palladium.
It’s important to note that the vast majority of the world’s platinum production comes from primary sources (ores rich in platinum-group elements), rather than from native platinum. Extracting platinum from its ores and processing it is a complex and energy-intensive industrial process. Platinum is highly prized for its luster, durability, and resistance to tarnish, making it a valuable material in various industries and for decorative purposes.
Physical, Chemical and Optical Properties of Platinum
Platinum is a unique and valuable metal with a range of physical, chemical, and optical properties that make it suitable for various industrial, scientific, and decorative applications. Here are some of the key properties of platinum:
Physical Properties:
Density: Platinum is a very dense metal, with a density of approximately 21.45 grams per cubic centimeter (g/cm³). This high density makes it heavy and gives it a substantial feeling.
Melting Point: Platinum has a very high melting point of around 1,768 degrees Celsius (3,214 degrees Fahrenheit). This high melting point makes it suitable for high-temperature applications.
Boiling Point: Platinum’s boiling point is even higher, at around 3,827 degrees Celsius (6,920 degrees Fahrenheit), making it resistant to vaporization at high temperatures.
Malleability and Ductility: Platinum is a highly malleable and ductile metal, which means it can be easily shaped, rolled, and drawn into various forms, making it ideal for jewelry and industrial processes.
Hardness: Platinum is a relatively soft metal compared to some other precious metals, but it is still harder than most base metals. Its hardness can be improved by alloying with other elements.
Color: Platinum has a distinctive silvery-white color, which contributes to its desirability for jewelry and other decorative purposes.
Chemical Properties:
Chemical Inertness: One of the most notable chemical properties of platinum is its resistance to corrosion and chemical reactions. It is highly inert and does not readily react with oxygen, water, or most common acids, making it an excellent choice for use in corrosive environments.
Catalytic Properties: Platinum is a highly effective catalyst for various chemical reactions. Its surface can facilitate reactions that are important in industries such as automotive (in catalytic converters) and chemical production.
Alloying: Platinum can be easily alloyed with other metals, such as iridium, palladium, and rhodium, to enhance its properties and create alloys with specific characteristics.
Optical Properties:
Luster: Platinum has a brilliant metallic luster, which adds to its visual appeal, making it a sought-after metal for jewelry and other ornamental purposes.
Reflectivity: Platinum is highly reflective, both in the visible and infrared spectra. This property is essential in applications like laboratory equipment and mirrors.
Transparency: Platinum is not transparent, as it is a dense metal that does not allow the passage of light. It is often used in the form of thin foils for some optical applications.
These properties make platinum a versatile and valuable material for various applications, ranging from jewelry and decorative items to industrial catalysts, laboratory equipment, and high-temperature engineering. Its exceptional resistance to corrosion and tarnish, coupled with its unique catalytic properties, make it an indispensable element in many technological and scientific fields.
Formation and Occurrence of Platinum
Platinum is a relatively rare and precious metal that is formed through natural geological processes. It is found in various geological settings as part of specific ore deposits. The formation and occurrence of platinum are influenced by its association with other elements, primarily nickel and copper. Here is an overview of how platinum is formed and where it is typically found:
Formation of Platinum:
Magmatic Processes: The primary source of it is magmatic ore deposits, which originate from the cooling and solidification of molten rock (magma) deep within the Earth’s mantle and crust. These deposits are associated with igneous rocks and are known as “platinum group element (PGE) deposits.” PGEs, including platinum, palladium, and rhodium, are often found together in these deposits.
Crystallization: During the cooling of magmas, minerals rich in platinum and other PGEs crystallize from the molten material. These minerals may include sulfides like sperrylite (PtAs2), cooperite (PtS), and braggite (Pt, Pd, Ni)S. Platinum is often found in combination with these minerals.
Occurrence of Platinum:
Layered Intrusions: One of the most significant geological settings for platinum deposits is in layered intrusions, which are large, layered igneous rock formations that often extend deep within the Earth’s crust. These intrusions are typically associated with ultramafic and mafic rock types and are characterized by the presence of platinum-rich sulfide minerals.
Ophiolite Complexes: Platinum deposits can also be found in ophiolite complexes, which are fragments of oceanic crust and upper mantle rocks that have been thrust onto continental landmasses. These complexes can contain platinum-bearing ore deposits, particularly in association with chromite ores.
Alluvial Deposits: In some cases, platinum is eroded from primary sources like layered intrusions and transported by rivers and streams. Over time, it can accumulate in alluvial deposits, often alongside other heavy minerals such as gold. This is where native platinum, which is nearly pure platinum metal, is occasionally found.
Residues from Industrial Processes: Platinum is sometimes a byproduct of various industrial processes, particularly those involving the refining of nickel and copper ores. In such cases, platinum is extracted from the residues of these processes.
It’s important to note that it is relatively rare in the Earth’s crust, and its mining and extraction can be economically challenging due to its low natural abundance. The largest producers of platinum are typically South Africa, Russia, and Zimbabwe, where significant deposits of platinum group elements are found.
The exploration and extraction of platinum are carried out using a combination of geological surveys, drilling, and mining techniques to locate and extract the metal from its primary sources, making it an essential resource for various industrial applications, including catalytic converters in automobiles and the production of high-value jewelry.
Application and Uses Areas
Platinum has a wide range of applications and is used in various industries due to its unique combination of physical and chemical properties. Some of its primary application areas and uses include:
Automotive Industry:
Catalytic Converters: It is a key component in catalytic converters, which are used to reduce harmful emissions from vehicles by converting pollutants like carbon monoxide (CO), hydrocarbons (HC), and nitrogen oxides (NOx) into less harmful substances. Palladium and rhodium, also part of the platinum group metals (PGMs), are used in catalytic converters alongside platinum.
Jewelry and Ornaments:
Precious Jewelry: Platinum is highly prized in the jewelry industry for its lustrous appearance, durability, and rarity. It is often used to make engagement rings, wedding bands, necklaces, and other fine jewelry.
Electronics:
Electrodes: Platinum’s excellent electrical conductivity, resistance to corrosion, and stability make it a valuable material for various electronic components, including electrodes used in devices like sensors, pacemakers, and high-precision measuring instruments.
Medical and Dental Applications:
Implants: Platinum is used in medical implants like pacemakers and stents due to its biocompatibility and resistance to corrosion within the human body.
Dental Restorations: Platinum can be found in dental alloys used for restorations such as crowns, bridges, and dental braces.
Industrial Processes:
Chemical Industry: Platinum serves as a catalyst in numerous chemical reactions, including the production of chemicals, pharmaceuticals, and petrochemicals.
Oil Refining: Platinum is used in the petroleum industry to catalyze various refining processes, such as the removal of impurities from crude oil and the production of high-octane gasoline.
Glass Manufacturing:
Glass Fiber Production: It is used in the production of high-quality glass fibers used in fiber optics and telecommunications.
Aerospace and Space Exploration:
Rocket Engines: Platinum’s high melting point and resistance to high temperatures make it suitable for use in rocket engines and aerospace components.
Renewable Energy:
Fuel Cells: It is used as a catalyst in hydrogen fuel cells, which can be employed for clean and efficient energy generation.
Solar Cells: It is used in the production of solar cells, where it helps improve the efficiency and longevity of the cells.
Laboratory and Scientific Equipment:
Crucibles: Platinum crucibles are used for high-temperature and high-purity applications in laboratories.
Thermocouples: It is used in thermocouples for precise temperature measurement.
Currency and Bullion:
Some countries, such as the Isle of Man and the United Kingdom, have used platinum coins as a form of currency.
Platinum bullion bars and coins are also traded as a form of investment.
It’s important to note that platinum is a relatively expensive and rare metal, which can influence its application in various industries. Additionally, the high cost of extraction and refining plays a role in determining the availability and usage of platinum in different sectors. Its unique properties, especially its catalytic abilities and resistance to corrosion, make it invaluable in applications where other materials fall short.
Mining Sources and Distribution
Mogolokwena Platinum Mine, South Africa
Platinum is primarily mined from specific geological sources and is not evenly distributed around the world. The majority of platinum production comes from a few key regions with significant platinum deposits. Here are some of the main mining sources and the distribution of platinum:
1. South Africa:
South Africa is the world’s largest producer of platinum, accounting for a substantial portion of the global supply. The Bushveld Complex in South Africa is a vast geological formation that contains numerous platinum group element (PGE) deposits, including platinum, palladium, rhodium, and others. Mines in this region, such as the Rustenburg and Mogalakwena mines, are among the most productive in the world.
2. Russia:
Russia is the second-largest producer of platinum globally. The majority of Russian platinum production comes from the Norilsk-Talnakh region in Siberia. The deposits here are also part of large PGE-rich intrusions.
3. Zimbabwe:
Zimbabwe is another significant producer of platinum. Mines like the Great Dyke project have contributed to Zimbabwe’s growing role in global platinum production.
4. Canada:
Canada is known for its platinum production from the Lac des Iles Mine in Ontario. Canadian platinum mining primarily extracts nickel along with platinum group elements.
5. United States:
The Stillwater Complex in Montana, United States, is a notable source of platinum and palladium. It is one of the few locations outside of South Africa and Russia with economically viable platinum mining.
6. Other Countries:
Several other countries also produce platinum to a lesser extent, including Australia, Colombia, and Botswana, among others.
It’s important to note that while it is found in various parts of the world, the largest and most productive deposits are concentrated in just a few regions. Additionally, platinum is often produced as a byproduct of other mining operations, particularly those focused on nickel and copper. The platinum group elements (PGEs), which include platinum, palladium, rhodium, iridium, ruthenium, and osmium, are often found together in these deposits.
The mining and extraction of platinum are capital-intensive processes, and the metal’s high market value reflects the challenges and costs associated with its production. Additionally, the availability of platinum can be influenced by factors such as political stability, economic conditions, and environmental regulations in the countries where it is mined. These factors can impact the global distribution of platinum and its supply to various industries, including the automotive and jewelry sectors.
References
Bonewitz, R. (2012). Rocks and minerals. 2nd ed. London: DK Publishing.
Handbookofmineralogy.org. (2019). Handbook of Mineralogy. [online] Available at: http://www.handbookofmineralogy.org [Accessed 4 Mar. 2019].
Mindat.org. (2019). Platinum: Mineral information, data and localities.. [online] Available at: https://www.mindat.org/ [Accessed. 2019].
Anorthoclase minerals is member of the sodium- and potassium-rich feldspar group takes its name from the Greek word anorthos, which means “not straight”—a reference to its oblique cleavage. Anorthoclase is colorless, white, cream, pink, pale yellow, gray, or green. Its crystals are prismatic or tabular and are often multiply twinned. Anorthoclase crystals can show two sets of fine lines at right angles to each other like microcline, but the lines are much finer. Specimens can also be massive or granular. Anorthoclase forms in sodium-rich igneous zones. It commonly occurs with ilmenite, apatite, and augite. Much anorthoclase exhibits a gold, bluish, or greenish schiller effect, making it one of several feldspars known as moonstone when cut en cabochon. A type of the igneous rock syenite called larvikite has large schillerized crystals of anorthoclase and is highly prized as an ornamental stone. Anorthoclase is widespread, but fine examples come from Cripple Creek, Colorado, USA; Larvik, Norway; and Fife, Scotland.
Name: From the Greek for oblique and fracture, descriptive of the
cleavage.
Mineral Group: Feldspar (alkali) group; intermediate between low sanidine and high albite.
Microcline grain in centre showing its distinctive cross-hatched twinning.
Microcline is one of the most common feldspar minerals. It can be colorless, white, cream to pale yellow, salmon pink to red, or bright green to blue-green. Microcline forms short prismatic or tabular crystals that are often of considerable size: single crystals can weigh several tons and reach yards in length. Crystals are often multiply twinned, with two sets of fine lines at right angles to each other. This gives a “plaid” effect that is unique to microcline among the feldspars. Microcline can also be massive. The mineral occurs in feldspar-rich rocks, such as granite, syenite, and granodiorite. It is found in granitepegmatites and in metamorphic rocks, such as gneisses and schists.
Polymorphism
& Series: Dimorphous with orthoclase.
Mineral
Group: Feldspar (alkali) group; (Si,Al) is
completely ordered in low microcline.
Microcline grain in centre showing its distinctive cross-hatched twinning.
Type
Anisotropic
Optical Extinction
Inclined extinction to cleavage
Twinning
Carlsbad, Baveno, Manebach,
polysynthetic on albite and pericline laws.
Optic Sign
Biaxial (-)
Birefringence
δ = 0.007 – 0.010
Relief
Low
Occurrence
Common in plutonic felsic rocks, as
granites, granite pegmatites, syenites; in metamorphic rocks of the greenschist
and amphibolite facies; in hydrothermal veins. A detrital component in
sedimentary rocks and as authigenic overgrowths.
Uses Areas
The most important place of use
is the production of porcelain.
Microcline is used industrially
in the production of glass and ceramic products.
It is used as ornamental
lapidary material with Amazonite in green color.
Sometimes feldspar is also used
in the manufacture of glass.
In the USA, at Amelia, Amelia Co., Virginia; Haddam, Middlesex Co., Connecticut; and Magnet Cove, Hot Spring Co., Arkansas.
In Colorado, in the Pikes Peak area, El Paso Co., Crystal Peak, Teller Co., with large crystals from the Devil’s Hole beryl mine, Fremont Co.; in the Black Hills, Pennington and Custer Cos., South Dakota.
Sanidine from Chastreix, Mont-Dore Massif, Puy-de-Dôme, FranceSanidine from Ophir dist., Oquirrh Mts, Tooele Co., Utah, UnitedSanidine Value, Price, and Jewelry Information
A member of the solid-solution series of potassium and sodium feldspars, sanidine is the high-temperature form of potassium feldspar, forming at 1,065°F (575°C) or above. Crystals are usually colorless or white, glassy, and transparent, but they may also be gray, cream, or occur in other pale tints. They are generally short prismatic or tabular, with a square cross section. Twinning is common. Crystals have been known to reach 20 in (50 cm) in length. Sanidine is also found as granular or cleavable masses. A widespread mineral, sanidine occurs in feldsparand quartz-rich volcanic rocks, such as rhyolite, phonolite, and trachyte. It is also found in eclogites, contact metamorphic rocks, and metamorphic rocks formed at low pressure and high temperature. Sanidine forms spherular masses of needlelike crystals in obsidian, giving rise to what is called snowflake obsidian. Significant occurrences of sanidine are at the Alban Hills near Rome, Italy; Mont St.-Hilaire, Canada; and Eifel, Germany
Name: From the Greek for tablet or board, in allusion to the mineral’s
common habit.
Polymorphism
& Series: High sanidine forms a series with
high albite.
Most common in felsic volcanic and
hypabyssal rocks as rhyolites, phonolites, trachytes; as spherulites in
volcanic glass. Also from ultrapotassic ma¯c, high-temperature contact
metamorphic (sanidinite facies), and hydrothermally altered rocks. From
eclogite nodules in kimberlite.
In Germany, from Drachenfels, Siebengebirge, Rhine; and at Hohenfels, Mendig, Mayen, and elsewhere around the Laacher See, Eifel district.
In France, at Mt. Dore, Auvergne, and Puy Gros du Laney, Puy-de-Dome.
From Vesuvius and Monte Somma, Campania, and Monte Cimine, Lazio, Italy.
At Daichi, Wakayama Prefecture, Japan.
From Kanchin-do, Meisem-gun, northeast Korea.
In the USA, at Tooele, Tooele Co., Utah; Cottonwood Canyon, Peloncillo Mountains, Cochise Co., Arizona; as large crystals in Rabb Canyon and near the crest of the Black Range, Grant Co., New Mexico. From Bernic Lake, Manitoba, and Mont Saint-Hilaire, Quebec, Canada.
In the Sierra de San Francisco, Durango, Mexico.
References
Bonewitz, R. (2012). Rocks and minerals. 2nd ed. London: DK Publishing.
Handbookofmineralogy.org. (2019). Handbook of Mineralogy. [online] Available at: http://www.handbookofmineralogy.org [Accessed 4 Mar. 2019].
Mindat.org. (2019). Sanidine: Mineral information, data and localities.. [online] Available at: https://www.mindat.org
An important rock-forming mineral, orthoclase is the potassium-bearing end member of the potassium sodium feldspar solid-solution series. It is a major component of granite its pink crystals give granite its typical color. Crystalline orthoclase can also be white, colorless, cream, pale yellow, or brownish red. Orthoclase appears as well-formed, short, prismatic crystals, which are frequently twinned. It may also occur in massive form. Moonstone is a variety of orthoclase that exhibits a schiller effect. Pure orthoclase is rare some sodium is usually present in the structure. Specimens are abundant in igneous rocks rich in potassium or silica, in pegmatites, and in gneisses. This mineral is important in ceramics, to make the item itself and as a glaze.
Name: From the Greek for straight and fracture, in allusion to the
cleavage angle.
Polymorphism
& Series: Dimorphous with microcline; forms a
series with celsian.
Mineral Group: Feldspar (alkali) group; (Al,Si) commonly only partially ordered.
Has perfect cleavage on {001} and
good cleavage on {010}. Cleavages intersect at 90°. It can be difficult to
see cleavage in thin section due to orthoclase’s low relief.
Widespread. Fine examples from St.
Gotthard, Ticino, and at Val Giuv, Tavetsch, GraubuÄnden, Switzerland. In the
Zillertal, Tirol, Austria. From Baveno, Piedmont, in the P¯tschtal,
Trentino-Alto Adige, and at San Piero in Campo, Elba, Italy. At Epprechtstein,
Bavaria, Carlsbad, Bohemia, and Manebach, Thuringia, Germany. From Cornwall,
England. In Russia, from the Mursinka-Alabashka area, near Yekaterinburg
(Sverdlovsk), Ural Mountains. In the USA, from Maine, at Paris and Buck¯eld,
Oxford Co; at Cornog, Chester Co., and Blue Hill and Lieperville, Delaware Co.,
Pennsylvania. In California, from the Pala and Mesa Grande districts, San Diego
Co.; in Colorado, on Mt. Antero, Cha®ee Co.; at Crystal Pass, Goodsprings,
Clark Co., Nevada. From Guanajuato, Mexico. At Tanokamiyama, Shiga Prefecture,
Japan. Gem crystals from Ampandrandava, Fianarantsoa, and Itrongay, near
Betroka, Madagascar.
References
Bonewitz, R. (2012). Rocks and minerals. 2nd ed. London: DK Publishing.
Handbookofmineralogy.org. (2019). Handbook of Mineralogy. [online] Available at: http://www.handbookofmineralogy.org [Accessed 4 Mar. 2019].
Mindat.org. (2019). Orthoclase: Mineral information, data and localities.. [online] Available at: https://www.mindat.org
Mineral deposits are accumulations of valuable minerals that are of economic interest to humans. These deposits can be found in a variety of geological settings, including igneous, sedimentary, and metamorphic rocks, and they are formed through a range of geological processes. The minerals in these deposits may be metals, such as copper, gold, or zinc, or nonmetals, such as salt or sulfur.
The basic concept behind mineral deposits is that valuable minerals are concentrated in certain areas of the Earth’s crust. This concentration can be the result of a number of factors, including magmatic processes, hydrothermal fluids, sedimentary processes, and weathering. The formation of mineral deposits can take millions of years, and they may be located at various depths below the surface of the Earth.
The discovery and development of mineral deposits is an important aspect of the mining industry, which provides the raw materials needed for many products and industries. Understanding the geological processes that lead to the formation of mineral deposits is important for locating and extracting these resources in an efficient and sustainable manner.
Mineral deposits can form through a variety of processes, some of which include:
Magmatic processes: Some mineral deposits are formed through the cooling and crystallization of magma. As magma cools and solidifies, it can precipitate minerals, which may accumulate to form ore bodies.
Hydrothermal processes: Hydrothermal fluids that are rich in dissolved minerals can deposit those minerals when they come into contact with cooler rock. Hydrothermal deposits are common in areas with active or recently active volcanoes, hot springs, and geysers.
Sedimentary processes: Sedimentary mineral deposits are formed by the accumulation of minerals in sedimentary rocks. These deposits can form through a variety of processes, such as precipitation from evaporating water, replacement of existing minerals, or the accumulation of minerals in pore spaces in sedimentary rocks.
Metamorphic processes: During metamorphism, mineral deposits can form through the recrystallization of existing minerals, the growth of new minerals, or the replacement of existing minerals by other minerals. Metamorphic mineral deposits are common in areas where rocks have been subjected to high temperature and pressure.
Placer processes: Placer deposits are formed by the accumulation of minerals in stream beds or on the surface of the ground. These deposits can form when minerals are eroded from their source rock and transported downstream by water or wind.
Weathering processes: Some mineral deposits can form through the weathering and decomposition of existing rocks. Weathering can cause the release of mineral ions into soil and groundwater, which can then accumulate to form mineral deposits.
Economic significance and uses
Mineral deposits are of great economic significance, as they are the source of many valuable resources used in various industries. The uses of minerals are diverse, ranging from construction materials such as cement, bricks, and tiles, to metals such as iron, copper, gold, and silver, to energy resources such as coal, oil, and natural gas.
In addition to their economic value, minerals also have many other uses, including in the manufacturing of electronics, jewelry, and other consumer goods, as well as in medicine and agriculture.
The economic value of a mineral deposit depends on various factors, such as the quality and quantity of the mineral, the ease of extraction, and the demand for the mineral in the market. Therefore, understanding the geology and mineralogy of mineral deposits is essential for assessing their economic potential and developing mining and extraction strategies.
Some common types of mineral deposits
There are many types of mineral deposits, but some of the most common ones include:
Vein deposits: These are formed by hydrothermal fluids that deposit minerals in fractures or fissures in rocks.
Porphyry deposits: These are formed by magma that intrudes into rocks and deposits minerals.
Skarn deposits: These are formed by hydrothermal fluids that react with carbonate rocks and deposit minerals in the resulting metamorphic rocks.
Sedimentary deposits: These are formed by the precipitation of minerals from water in sedimentary environments.
Placer deposits: These are formed by the concentration of heavy minerals in streams, beaches, or other sedimentary environments.
Volcanogenic massive sulfide (VMS) deposits: These are formed by hydrothermal fluids that deposit minerals in volcanic rocks.
Carbonatite deposits: These are formed by magma that contains high concentrations of carbonate minerals.
Kimberlite pipes: These are formed by the eruption of magma that contains diamonds and other minerals.
Iron oxide-copper-gold (IOCG) deposits: These are formed by hydrothermal fluids that deposit iron, copper, and gold in rocks.
Laterite deposits: These are formed by the weathering of ultramafic rocks and the concentration of nickel and other metals in the resulting soils.
These are just a few examples, and there are many other types of mineral deposits that can form in different geological settings.
Vein-Mineral-Deposits
Vein deposits are a type of mineral deposit that form when minerals are deposited from hydrothermal fluids within cracks, fissures, or joints in rocks. They are often found within rocks that have undergone deformation or metamorphism. The minerals that make up vein deposits are often metal ores, although non-metallic minerals can also be deposited in veins.
Vein deposits are formed when hot, mineral-rich fluids flow through fractures in rocks and cool, causing the minerals to precipitate out and form veins. The fluids that form vein deposits are often associated with magmatic or hydrothermal systems, and can be sourced from a variety of different rocks, including plutonic rocks, volcanic rocks, and sedimentary rocks.
Some examples of vein deposits include gold veins in the Black Hills of South Dakota, silver veins in the Comstock Lode in Nevada, and copper veins in the Keweenaw Peninsula of Michigan. Vein deposits are often economically valuable, as they can contain high concentrations of valuable minerals.
There are various types of mineral deposits, each with its own unique characteristics and formation processes. Some of the most common types of mineral deposits include:
Magmatic deposits: These are formed by the cooling and crystallization of magma and include deposits of chromite, platinum, nickel, and copper.
Hydrothermal deposits: These are formed by the circulation of hot aqueous fluids and include deposits of gold, silver, lead, zinc, and copper.
Sedimentary deposits: These are formed by the accumulation and concentration of mineral particles in sedimentary rocks and include deposits of iron, manganese, uranium, and phosphate.
Residual deposits: These are formed by the weathering and leaching of rocks, leaving behind the concentrated minerals, and include deposits of bauxite and iron.
Placer deposits: These are formed by the concentration of minerals from weathering and erosion in streambeds and beach sands and include deposits of gold, tin, and diamonds.
Carbonatite deposits: These are rare and formed by the cooling and solidification of carbonatite magma and include deposits of rare earth elements and niobium.
Kimberlite deposits: These are formed by deep-seated volcanic activity and include deposits of diamonds.
Evaporite deposits: These are formed by the evaporation of saline water and include deposits of halite, gypsum, and potash.
Laterite deposits: These are formed by the weathering of ultramafic rocks in tropical climates and include deposits of nickel and cobalt.
Iron oxide-copper-gold (IOCG) deposits: These are formed by hydrothermal fluids and include deposits of iron, copper, and gold.
Each type of mineral deposit has its own distinct characteristics, and the exploration and development of a particular deposit type require specialized techniques and knowledge.
Primary mineralogy
Primary mineralogy refers to minerals that form directly from igneous, metamorphic, and sedimentary processes. These minerals are formed in their present location, and they have not been transported or altered from their original state. Primary minerals are often classified based on their crystal structure, which is determined by the mineral’s chemistry and how it was formed.
In igneous rocks, the minerals that form are mainly silicate minerals, which contain silicon and oxygen, along with other elements such as aluminum, magnesium, iron, and potassium. Some of the common primary silicate minerals found in igneous rocks include feldspar, quartz, mica, pyroxene, amphibole, and olivine.
Metamorphic rocks are formed from the alteration of pre-existing rocks due to changes in temperature, pressure, and chemical environment. The primary minerals that form during metamorphism are typically silicate minerals, but they are often different from the minerals found in the original rock. For example, the mineral garnet often forms during metamorphism of shale or sandstone.
Sedimentary rocks are formed from the accumulation of sediment that has been transported and deposited by wind, water, or ice. The primary minerals that form in sedimentary rocks are typically non-silicate minerals, such as calcite, dolomite, gypsum, and halite.
Primary mineralogy is important in the study of geology because it provides clues about the history of the Earth’s crust and the processes that have formed rocks and minerals. By studying the composition and distribution of primary minerals, geologists can gain insights into the geologic history of an area, and can better understand the resources that are present.
Secondary minerals are minerals that are formed through the alteration of pre-existing minerals, typically as a result of exposure to hydrothermal fluids or weathering processes.
In some cases, secondary minerals are formed by the reaction of pre-existing minerals with fluids that are enriched in certain elements, such as water that has been heated by magma or groundwater that has been enriched with metal ions from a mineral deposit. In other cases, secondary minerals form through weathering processes that can break down pre-existing minerals and release their chemical constituents, which then recombine to form new minerals.
Examples of secondary minerals include serpentine, which is formed through the alteration of ultramafic rocks, and kaolinite, which is formed through the weathering of feldspar minerals in granite. Secondary minerals can be economically important, as they may contain valuable metals and minerals that were not present in the original rock or mineral.
In geology, the term “host rock” refers to the rock that surrounds, encases, or contains an ore deposit, mineral vein, or other geological feature of interest. The host rock can be either sedimentary, igneous, or metamorphic in origin, and the mineralization or deposit that it contains may be associated with the host rock’s formation or intrusion.
In the context of mining, understanding the characteristics of the host rock is critical in determining the feasibility and potential profitability of a mining project. The type of host rock, its mineral composition, structure, and other properties can affect the ease with which the minerals or metals can be extracted, as well as the costs associated with extraction and processing.
The rock within which ore deposit occurs
Volcanic or pyroclastic rocks
Plutonic or subvolcanic rocks
Ultramafic rocks
Carbonate rocks
Sedimentary rocks
Evaporitic rocks
Wall rock or country rock
In geology, the term “wall rock” or “country rock” refers to the surrounding rock that encloses an igneous intrusion, ore deposit, or mineral vein. Wall rocks are usually older than the intrusive or mineralizing event that they surround, and may have been altered by the heat and fluids associated with the intrusion or mineralization.
For example, in the context of a mineral vein, the wall rock is the rock that is in contact with the vein, and it can be an important factor in the formation and characteristics of the vein. Wall rocks can also influence the type of mineralization that occurs, as well as the shape and orientation of the deposit. Understanding the properties and characteristics of wall rocks is an important part of mineral exploration and mining.
The rock which surrounds the ore deposit, in particular, the rock on either side of a vein
Volcanic or pyroclastic rocks
Plutonic or subvolcanic rocks
Ultramafic rocks
Carbonate rocks
Sedimentary rocks
Evaporitic rocks
References
Guilbert, J. M., & Park Jr, C. F. (2007). The geology of ore deposits (2nd ed.). Waveland Press.
Evans, A. M. (1993). Ore geology and industrial minerals: an introduction (2nd ed.). Blackwell Science.
Proffett, J. M. (2003). Geology of the mineral deposits of Australia and Papua New Guinea (3rd ed.). AusIMM.
Sillitoe, R. H. (2010). Porphyry copper systems. Economic Geology, 105(1), 3-41.
Heinrich, C. A., Driesner, T., & Monecke, T. (2007). The geology of hydrothermal ore deposits. Economic Geology, 102(3), 469-505.
Hofstra, A. H., Cline, J. S., & Deutsch, C. V. (2000). Chapter 23 – Gold deposits. In Geology of the mineral deposits of the Cordillera of western Canada (pp. 705-762). Canadian Institute of Mining, Metallurgy and Petroleum.
Ridley, J. R., & Diamond, L. W. (2014). The nature and origin of gold deposits of the Witwatersrand conglomerates in the Ventersdorp Supergroup, South Africa – a reappraisal. Ore Geology Reviews, 62, 156-177.
Kesler, S. E., Wilkinson, B. H., & Kesler, S. E. (2012). Ore deposit geology. Cambridge University Press.
Hedenquist, J. W., & Lowenstern, J. B. (1994). The role of magmas in the formation of hydrothermal ore deposits. Nature, 370(6490), 519-527.
Hoefs, J. (2009). Stable isotope geochemistry (6th ed.). Springer.
Volcanology is the scientific discipline that focuses on the study of volcanoes, volcanic processes, and the related phenomena that occur within the Earth’s crust. It encompasses a wide range of scientific fields, including geology, geophysics, geochemistry, and more. Volcanologists study the behavior, formation, eruption mechanisms, and impacts of volcanoes to better understand their nature and mitigate potential hazards.
What are Volcanoes? Volcanoes are geological formations that result from the accumulation of molten rock, ash, and gases beneath the Earth’s surface. These materials are expelled through openings or vents in the Earth’s crust during volcanic eruptions. The material that is ejected during eruptions can vary widely, including lava flows, pyroclastic flows (mixtures of ash, rock fragments, and gas), volcanic gases (such as water vapor, carbon dioxide, sulfur dioxide), and even volcanic ash that can reach high into the atmosphere.
Importance of Studying Volcanoes: Studying volcanoes is of paramount importance due to their potential to cause significant geological and environmental impacts. Here are some key reasons why the study of volcanoes is crucial:
Hazard Mitigation: Understanding the behavior and activity of volcanoes allows scientists to predict eruptions, assess their potential impacts, and issue timely warnings to local populations. This can save lives and minimize damage to property and infrastructure.
Environmental Impact: Volcanic eruptions can release large amounts of gases and particulates into the atmosphere. These can affect climate patterns, air quality, and the ozone layer. Studying volcanic emissions contributes to a better understanding of these impacts.
Geological Insights: Volcanic activity provides valuable information about the Earth’s internal processes and the movement of molten rock and materials within the planet’s crust. This knowledge helps scientists understand plate tectonics and the formation of Earth’s surface features.
Natural Resources: Volcanic environments often host valuable mineral deposits, geothermal energy sources, and unique ecosystems. Understanding the geological processes associated with volcanism can aid in resource exploration and sustainable development.
Historical and Cultural Significance: Volcanoes have played a significant role in shaping landscapes and influencing human cultures throughout history. Studying past volcanic events helps researchers reconstruct Earth’s history and understand the interactions between humans and their natural surroundings.
Scientific Advances: Researching volcanoes leads to advancements in various scientific disciplines, including geology, physics, chemistry, and meteorology. Insights gained from studying volcanic processes can contribute to broader scientific understanding.
In summary, volcanology is a multidisciplinary field that delves into the study of volcanoes and their various aspects, including their formation, eruptions, impacts, and contributions to Earth’s dynamic processes. By examining volcanoes, scientists gain insights that are not only valuable for geological understanding but also for safeguarding communities and ecosystems from potential volcanic hazards.
Plate Tectonics and Volcanic Activity: Volcanic activity is closely linked to the movement of tectonic plates on the Earth’s surface. The Earth’s outer shell, known as the lithosphere, is divided into several large and small tectonic plates that interact at their boundaries. There are three main types of plate boundaries where volcanic activity is commonly observed:
Divergent Boundaries: At divergent boundaries, tectonic plates move away from each other. As the plates separate, magma from the mantle can rise to fill the gap, leading to the formation of new crust and underwater volcanoes. This process is seen at mid-ocean ridges, where the oceanic crust is created.
Convergent Boundaries: At convergent boundaries, two tectonic plates move towards each other. If one of the plates is oceanic and the other is continental or oceanic, the denser oceanic plate may sink beneath the other in a process known as subduction. Subduction zones are often associated with explosive volcanic activity as the subducted plate melts and forms magma that rises to the surface.
Transform Boundaries: At transform boundaries, tectonic plates slide past each other horizontally. While volcanic activity is not as common at these boundaries, it can occur in some cases where magma is able to reach the surface through fractures in the crust.
Types of Volcanoes Based on Shape:
Shield Volcanoes: These are broad, gently sloping volcanoes characterized by their wide, flat profiles. They are formed by the accumulation of numerous low-viscosity lava flows, which can travel over long distances before solidifying. Shield volcanoes typically have non-explosive eruptions and are often found at divergent boundaries or over hotspots.
Stratovolcanoes (Composite Volcanoes): Stratovolcanoes are steep-sided volcanoes with layered structures. They are formed by alternating eruptions of lava flows, pyroclastic material (ash, rocks, and gas), and volcanic debris. These eruptions can be explosive and result in significant ash clouds and pyroclastic flows. Stratovolcanoes are often found at convergent boundaries, especially in subduction zones.
Cinder Cone Volcanoes: These are small, conical volcanoes composed of pyroclastic fragments such as ash, cinders, and volcanic rocks. Cinder cone eruptions are typically short-lived and produce relatively minor eruptions compared to other types of volcanoes. They can form independently or on the flanks of larger volcanoes.
Types of Volcanoes Based on Eruption Style:
Effusive Eruptions: These eruptions involve the relatively gentle release of lava from the volcano. Lava flows may spread over the surrounding terrain, gradually building up the volcano’s shape. Shield volcanoes are often associated with effusive eruptions.
Explosive Eruptions: Explosive eruptions are characterized by the sudden release of trapped gases, creating powerful explosions that can produce ash clouds, pyroclastic flows, and volcanic debris. Stratovolcanoes and cinder cone volcanoes are more likely to experience explosive eruptions.
Phreatomagmatic Eruptions: These eruptions occur when magma comes into contact with water, such as groundwater, lakes, or oceans. The interaction between water and magma leads to explosive steam-driven eruptions, generating fine ash and forming craters. These eruptions can occur at various types of volcanoes.
Understanding the various types of volcanoes and their formations is essential for predicting eruption behavior, assessing volcanic hazards, and ensuring the safety of communities in volcanic regions.
Volcanic Processes
Magma Generation and Composition: Magma is molten rock that forms beneath the Earth’s surface. It is generated when solid rock in the Earth’s mantle undergoes partial melting due to high temperatures and/or decreased pressure. The composition of magma depends on the chemical composition of the rocks being melted. The main components of magma are:
Silica (SiO2): A major determinant of magma viscosity. High-silica magmas are more viscous and tend to result in explosive eruptions due to trapped gas and pressure buildup.
Volatiles: These include water vapor (H2O), carbon dioxide (CO2), sulfur dioxide (SO2), and other gases dissolved in the magma. Volatiles play a crucial role in determining the eruption style and can influence the explosiveness of volcanic eruptions.
Minerals: As magma cools, minerals crystallize out of the melt. The minerals present in magma are determined by factors such as temperature, pressure, and chemical composition.
Magma Ascent and Eruption Mechanisms: The ascent of magma from the mantle to the surface is driven by the buoyancy of the less dense molten rock. As magma rises, it encounters different levels of pressure and changes in its environment. The following processes contribute to magma ascent and volcanic eruptions:
Gas Expansion: As magma rises, the decrease in pressure allows dissolved gases to expand rapidly, leading to the formation of gas bubbles. If the gas content is high and the magma is viscous, pressure can build up, potentially resulting in explosive eruptions.
Fragmentation: When gas bubbles in magma expand rapidly, they can rupture the magma into smaller fragments. These fragments, along with ash and volcanic debris, can be ejected explosively during eruptions.
Conduit Formation: Magma creates pathways called conduits as it moves towards the surface. These conduits can become lined with solidified magma (dikes) and may help direct the flow of magma during eruptions.
Plinian Eruptions: These are highly explosive eruptions characterized by the ejection of enormous columns of ash and gas high into the atmosphere. These eruptions can result in the formation of calderas, large volcanic depressions.
Role of Gases in Volcanic Activity: Gases dissolved in magma play a critical role in determining the behavior of volcanic eruptions:
Explosivity: The presence of volatile gases, such as water vapor and carbon dioxide, can increase the pressure within the magma, leading to more explosive eruptions.
Gas Content: The amount of gas in magma can influence the magma’s viscosity. Higher gas content tends to reduce magma viscosity, allowing it to flow more easily.
Gas Release: As magma approaches the surface, decreasing pressure allows gases to rapidly exsolve from the magma, forming bubbles that can propel magma fragments and ash into the air.
Pyroclastic Flows and Lahars: Pyroclastic flows are fast-moving avalanches of hot gas, ash, and volcanic fragments that race down the slopes of a volcano during an eruption. These flows can be extremely destructive and are often a result of explosive eruptions. Lahars, on the other hand, are volcanic mudflows or debris flows that can occur when volcanic material mixes with water, such as rainfall or melted snow and ice. Lahars can travel great distances from the volcano’s summit and can be hazardous to communities located downstream.
Monitoring and Prediction of Volcanic Activity
Monitoring and predicting volcanic activity are essential for mitigating the potential hazards associated with volcanic eruptions. Various tools and techniques are used to monitor volcanoes and assess their behavior, with the goal of providing early warnings to at-risk populations. Here are some key aspects of monitoring and prediction:
1. Seismic Monitoring: Seismic instruments detect ground vibrations caused by volcanic activity, such as the movement of magma or the fracturing of rocks. Changes in seismic activity, including the frequency and magnitude of earthquakes, can provide insights into the movement of magma beneath the surface and indicate possible eruption scenarios.
2. Ground Deformation Monitoring: Volcanic activity can cause the ground to deform due to the movement of magma. Instruments like GPS and satellite-based radar can measure these deformations, helping scientists understand magma migration and the potential for eruptions.
3. Gas Emission Monitoring: Volcanic gases, such as sulfur dioxide and carbon dioxide, can be released in larger amounts before an eruption. Gas monitoring helps assess the buildup of pressure within the volcano and provides information about the magma’s ascent.
4. Thermal Imaging: Infrared cameras can detect changes in temperature on a volcano’s surface. An increase in temperature might indicate the movement of magma toward the surface.
5. Remote Sensing: Satellites equipped with various sensors can provide valuable information about volcanic activity, such as thermal anomalies, gas emissions, and ground deformation, from a distance.
6. Volcano Geology and History: Studying a volcano’s geological history and past eruption patterns can help scientists predict potential future behavior. Patterns of eruptions, such as the interval between events, can inform hazard assessments.
7. Computer Models: Mathematical models that simulate volcanic processes can help predict how eruptions might unfold. These models take into account data collected from monitoring efforts to forecast potential scenarios.
8. Early Warning Systems: Combining data from various monitoring techniques, scientists can develop early warning systems that alert authorities and communities about impending volcanic activity. These warnings can provide critical time for evacuation and preparation.
9. Public Education and Preparedness: An important aspect of prediction is ensuring that local communities are educated about volcanic hazards and know how to respond to warnings. Preparedness plans and regular drills can save lives in the event of an eruption.
10. Challenges and Limitations: While significant advancements have been made in volcanic monitoring and prediction, challenges remain. Volcanic systems are complex, and eruptions can be unpredictable. Some eruptions occur with little or no warning, while others might show signs of activity for weeks, months, or even years without leading to a major eruption. Moreover, false alarms can have serious economic and social consequences.
In summary, monitoring and predicting volcanic activity involve the integration of various scientific disciplines and technologies. The goal is to provide timely and accurate information to safeguard lives and property in volcanic regions. While challenges persist, ongoing research and advancements continue to improve our ability to understand and forecast volcanic behavior.
Volcanic Hazards and Risk Mitigation
Volcanic hazards are the potential dangers posed by volcanic activity to human populations, infrastructure, and the environment. These hazards can have a wide range of impacts, from local to global scales. Effective risk mitigation strategies are essential to minimize the negative consequences of volcanic eruptions. Here are some common volcanic hazards and strategies for mitigating their risks:
1. Pyroclastic Flows: Pyroclastic flows are fast-moving mixtures of hot gas, ash, and volcanic fragments. They can devastate everything in their path. Mitigation strategies include:
Zoning: Identifying and designating hazard zones around active volcanoes to restrict human settlements.
Early Warning Systems: Establishing systems to provide timely alerts about imminent pyroclastic flows, allowing for evacuation.
2. Lahars (Volcanic Mudflows): Lahars are fast-moving flows of water, volcanic ash, and debris that can inundate areas downstream from a volcano. Mitigation strategies involve:
Awareness and Education: Ensuring that communities downstream are aware of the lahars’ potential and have evacuation plans in place.
Physical Barriers: Constructing structures like levees to divert or contain lahars and prevent them from reaching populated areas.
3. Ashfall: Volcanic ash can cause widespread disruption, affecting air travel, infrastructure, and agriculture. Mitigation strategies include:
Volcanic Ash Advisories: Providing real-time information to aviation authorities to reroute or ground flights during ashfall.
Infrastructure Design: Constructing buildings and infrastructure resistant to ash accumulation and damage.
4. Volcanic Gases: Volcanic gases can pose health risks to people living near active volcanoes. Mitigation strategies include:
Gas Monitoring: Continuously monitoring gas emissions to assess potential health risks and issue advisories.
Respiratory Protection: Providing masks or respirators to residents in high-risk areas during eruptions.
5. Lava Flows: Lava flows can destroy structures and infrastructure in their path. Mitigation strategies involve:
Land Use Planning: Prohibiting construction in areas with a high risk of lava flow impact.
Monitoring and Early Warning: Providing advance notice of impending lava flows to allow evacuation.
6. Tsunamis: Volcanic activity, particularly in island settings, can trigger tsunamis when a large volume of volcanic material enters the ocean. Mitigation strategies include:
Tsunami Warning Systems: Installing systems to detect underwater earthquakes or volcanic activity that might trigger tsunamis.
Evacuation Plans: Developing plans for coastal communities to move to higher ground in the event of a tsunami warning.
7. Ash Dispersal and Climate Effects: Volcanic ash can be carried long distances by wind, impacting air travel and climate patterns. Mitigation strategies include:
Aviation Advisories: Providing real-time information to air traffic control to ensure safe flight paths.
Climate Modeling: Using computer models to predict the dispersal and effects of ash on climate.
8. Community Preparedness and Education: Empowering local communities with knowledge about volcanic hazards and preparedness measures can save lives. Public education campaigns, evacuation drills, and community engagement are crucial aspects of mitigation.
9. Land Use Planning: Government regulations and land use planning that restrict development in high-risk volcanic areas can reduce exposure to hazards.
10. International Collaboration: Volcanic hazards can transcend national boundaries. Collaborative efforts between countries and international organizations are important for sharing expertise and resources.
In summary, effective mitigation of volcanic hazards requires a multi-pronged approach that includes scientific monitoring, early warning systems, public education, infrastructure design, and land use planning. By combining these strategies, communities can reduce the potential impact of volcanic eruptions and ensure the safety and well-being of their residents.
Volcanic Landforms and Features
Volcanic Crater
Volcanic activity gives rise to a diverse range of landforms and features on the Earth’s surface. These formations are a result of various volcanic processes, including the eruption of lava, the accumulation of volcanic debris, and the modification of the landscape over time. Here are some notable volcanic landforms and features:
Volcanic Caldera
1. Crater: A crater is a depression at the summit of a volcano. It can form during an eruption when material is ejected from the vent, creating a void at the top of the volcano.
2. Caldera: A caldera is a large, circular depression that forms when the summit of a volcano collapses after a massive eruption. Calderas can be several kilometers in diameter and are often surrounded by steep walls.
3. Volcanic Cones: Volcanic cones are mound-like structures built up from the accumulation of volcanic material. They come in different shapes, including cinder cone volcanoes, which are formed from ejected pyroclastic fragments.
4. Lava Plateaus: Lava plateaus are extensive flat or gently sloping areas formed by the accumulation of lava flows over time. They can cover large regions and are often associated with effusive eruptions.
5. Lava Tubes: Lava tubes are tunnels formed by the solidification of the outer layers of flowing lava. When the lava flow inside drains away, it leaves behind a hollow tube-like structure.
6. Fissure Eruptions: Fissure eruptions occur along elongated fractures in the Earth’s crust. These eruptions can produce extensive lava flows that cover a wide area, forming features like lava plateaus.
7. Maar: A maar is a shallow, wide crater formed by explosive eruptions caused by the interaction of magma with groundwater. Maars often fill with water, creating crater lakes.
8. Tuff Rings and Tuff Cones: These features are created when volcanic explosions eject ash and debris into the air. The material falls back to the ground and accumulates to form a circular or cone-shaped mound.
9. Lava Domes (Volcanic Domes): Lava domes are formed when thick, viscous lava accumulates near a volcano’s vent. They often have steep sides and can grow slowly over time.
10. Fumaroles and Geysers: Fumaroles are vents that release volcanic gases and steam into the atmosphere. Geysers are hot springs that periodically erupt with steam and water due to heated groundwater.
11. Hot Springs and Geothermal Features: Volcanic activity can heat groundwater, creating hot springs and geothermal features that are used for bathing and energy generation.
12. Volcanic Islands: Volcanic islands are formed when volcanic activity occurs underwater, resulting in the accumulation of volcanic material above sea level. Many oceanic islands are of volcanic origin.
13. Volcanic Ash Plains: Areas covered by volcanic ash deposits from eruptions can create flat plains or gently undulating landscapes with a layer of fine volcanic material.
These are just a few examples of the wide variety of volcanic landforms and features that can be found around the world. Each type of landform provides insights into the geological processes and history of volcanic activity in a region.
Volcanism and Climate
Volcanic eruptions can have significant effects on the Earth’s climate, both in the short term and over longer timescales. These effects are primarily caused by the release of large amounts of gases, aerosols, and particles into the atmosphere during volcanic activity. Here’s how volcanism can influence climate:
1. Aerosols and Particles: Volcanic eruptions can inject large quantities of fine particles and aerosols into the stratosphere. These particles can reflect sunlight back into space, leading to a temporary cooling effect on the planet’s surface. This phenomenon is known as “volcanic cooling” or the “volcanic aerosol effect.”
2. Sulfur Dioxide (SO2) and Sulfate Aerosols: Volcanic eruptions release sulfur dioxide (SO2) into the atmosphere, which can react with water vapor to form sulfate aerosols. These aerosols can persist in the stratosphere for months to years, reflecting sunlight and reducing the amount of solar radiation reaching the Earth’s surface. This can lead to a decrease in global temperatures, sometimes referred to as a “volcanic winter.”
3. Climate Impacts:
Short-Term Cooling: The injection of sulfur dioxide and aerosols into the atmosphere can lead to short-term cooling effects. Notable historical examples include the 1815 eruption of Mount Tambora, which caused the “Year Without a Summer” in 1816 due to the cooling influence of volcanic aerosols.
Long-Term Effects: While the cooling effects of individual volcanic eruptions are temporary, the cumulative impact of multiple eruptions over centuries or millennia can contribute to long-term climate fluctuations. Volcanic activity has been linked to periods of colder climate in the past.
4. Volcanic Gases and Climate:
Carbon Dioxide (CO2): While volcanic eruptions release carbon dioxide, the amounts are relatively small compared to human activities such as burning fossil fuels. The CO2 emitted by volcanic activity is generally balanced by the CO2 absorbed by volcanic rocks and oceans over geological timescales.
Climate Feedbacks: Volcanic cooling due to aerosols and particles can trigger feedback mechanisms. For instance, reduced temperatures can lead to decreased evaporation and cloud cover, which in turn affects the planet’s energy balance.
5. Supervolcano Eruptions and Long-Term Climate Impact: Massive volcanic eruptions, such as those associated with supervolcanoes, can release enormous volumes of volcanic material into the atmosphere. These eruptions have the potential to cause more substantial and longer-lasting climate impacts, leading to significant cooling and potential disruptions to ecosystems and agriculture.
6. Climate Modeling and Study: Scientists use climate models to simulate the impact of volcanic eruptions on the Earth’s climate. By analyzing historical records of volcanic activity and its climatic consequences, researchers aim to better understand the complex interactions between volcanism and climate.
In summary, volcanic eruptions can temporarily influence the Earth’s climate by releasing aerosols and gases that alter the balance of energy in the atmosphere. While individual eruptions have short-term effects, the cumulative impact of volcanic activity over time can contribute to climate variability. Understanding the interactions between volcanism and climate is crucial for predicting potential climatic responses to future volcanic events and for enhancing our understanding of natural climate fluctuations.
Volcanoes and Human History
Volcanic activity has played a significant role in shaping human history and cultures throughout the ages. From providing fertile soil for agriculture to triggering catastrophic events that have altered societies, volcanoes have left a lasting impact on civilizations. Here are some ways in which volcanoes have influenced human history:
1. Agriculture and Fertile Soil: Volcanic soils, known as volcanic ash or “tephra,” are rich in minerals and nutrients that can enhance soil fertility. Many societies have settled near volcanoes due to the fertile land they provide, leading to the development of agricultural economies.
2. Settlements and Trade Routes: Volcanic regions often attract human settlements due to the availability of resources like minerals, hot springs, and geothermal energy. These areas also served as hubs for trade and cultural exchange.
3. Cultural Beliefs and Myths: Volcanic eruptions often evoke awe and fear, leading to the development of myths and religious beliefs centered around volcanoes. Many cultures have associated volcanoes with gods or spirits, attributing eruptions to divine forces.
4. Architecture and Building Materials: Volcanic rocks, such as basalt and pumice, have been used as construction materials for centuries. The use of volcanic stone in buildings and monuments is prevalent in regions with volcanic activity.
5. Disaster and Survival: While volcanic activity can be a source of fertility, it can also be catastrophic. Eruptions have caused widespread destruction, displacing populations and affecting food sources. Communities living near volcanoes have developed strategies to mitigate risks and adapt to volcanic hazards.
6. Pompeii and Herculaneum: One of the most famous examples of volcanic impact on human history is the eruption of Mount Vesuvius in 79 AD, which buried the Roman cities of Pompeii and Herculaneum under layers of ash and volcanic material. The preservation of these cities in volcanic debris offers insights into daily life in ancient Rome.
7. Climate Impact: Large volcanic eruptions can inject aerosols and particles into the atmosphere, leading to temporary cooling of the Earth’s climate. Some historians believe that volcanic activity contributed to periods of cooler climate, affecting agriculture and civilizations.
8. Art and Literature: Volcanic eruptions have inspired art, literature, and cultural expressions across different societies. Eruptions have been depicted in paintings, poems, and stories, reflecting human fascination with the power and unpredictability of nature.
9. Tourism and Education: Volcanic landscapes attract tourists and researchers alike. Volcanoes and volcanic features provide opportunities for adventure tourism, geological studies, and educational experiences.
10. Future Challenges: As human populations continue to expand, more people are living in proximity to active volcanoes, increasing the potential for impacts from volcanic hazards. Developing effective disaster preparedness and mitigation strategies is crucial for minimizing the risks associated with volcanic activity.
In summary, volcanoes have had a profound influence on human history, from shaping landscapes and cultures to providing resources and posing challenges. The interactions between volcanoes and societies highlight the complex relationship between humans and the natural world.
Volcanic Exploration and Research
Tools and Techniques Used by Volcanologists: Volcanologists employ a range of tools and techniques to study volcanoes and their associated processes. These tools help them gather data and insights into volcanic behavior, eruption mechanisms, and the underlying geological processes. Some common tools and techniques include:
Seismic Monitoring: Seismometers detect ground vibrations caused by volcanic activity, helping to track magma movement, earthquakes, and potential eruption signals.
GPS and Satellite Observations: Global Positioning System (GPS) receivers and satellite-based radar track ground deformation, helping scientists monitor changes in the volcano’s shape and detect uplift or subsidence.
Gas Analyses: Instruments measure the composition and quantity of gases emitted by volcanoes, providing information about magma movement, degassing processes, and potential eruption indicators.
Remote Sensing: Satellite sensors and drones capture images and data from above, allowing scientists to study volcanic features, deformation, and changes in real time.
Thermal Imaging: Infrared cameras detect temperature changes on the volcano’s surface, revealing areas of heat accumulation, fumaroles, and active vents.
Geochemical Analysis: Researchers study the chemical composition of volcanic rocks, gases, and minerals to understand magma sources, processes, and evolution.
Fieldwork in Volcanic Environments: Fieldwork is a fundamental aspect of volcanological research. Volcanologists conduct on-site investigations to collect samples, install monitoring equipment, and directly observe volcanic phenomena. Fieldwork includes activities such as:
Sample Collection: Collecting rock, ash, and gas samples provides crucial information about a volcano’s history, composition, and eruption potential.
Deploying Instruments: Installing seismometers, GPS receivers, gas analyzers, and other monitoring equipment on and around volcanoes helps gather real-time data.
Observations and Mapping: Detailed observations of volcanic features, deposits, and geological formations help researchers understand eruption dynamics and history.
Risk Assessment: Fieldwork also involves assessing potential hazards and vulnerabilities of nearby communities, helping to inform emergency planning and preparedness.
Volcanic Research for Understanding Earth’s Interior Processes: Volcanic research contributes to our understanding of the Earth’s internal processes, including the movement of tectonic plates and the composition of the mantle. By studying volcanic activity, scientists can:
Plate Tectonics: Volcanic activity often occurs at tectonic plate boundaries, providing insights into the movement and interactions of these plates.
Magma Generation: Studying volcanic rocks and gases helps researchers understand how magma forms and rises through the Earth’s crust.
Mantle Composition: Volcanic materials originate from the Earth’s mantle, offering a window into its composition and dynamics.
Earthquake Studies: Volcanic regions are often seismically active. Studying earthquake patterns helps researchers understand the processes leading to volcanic activity.
Climate Impact: Volcanic eruptions can impact the Earth’s climate. Researching past eruptions provides historical records of climate impacts.
In summary, volcanologists use a variety of tools, techniques, and fieldwork methods to explore and research volcanic activity. This research not only enhances our understanding of Earth’s internal processes but also contributes to hazard assessment and preparedness efforts to mitigate the impact of volcanic events on human populations and the environment.
Conclusion
Volcanology, the scientific study of volcanoes and volcanic activity, is a crucial field with wide-ranging implications for our understanding of Earth’s dynamic processes and the safety of human populations. Throughout this discussion, we’ve explored the diverse aspects of volcanology, from the formation and types of volcanoes to their role in shaping landscapes, cultures, and climate. Let’s recap the key points:
Importance of Volcanology:
Volcanology plays a vital role in predicting and mitigating the hazards posed by volcanic eruptions, saving lives and safeguarding communities.
Studying volcanoes provides insights into geological processes, plate tectonics, and the movement of magma within the Earth’s crust.
Volcanic activity influences climate patterns, affecting local and global weather conditions.
Ongoing Relevance in Understanding Geological Processes:
Volcanic research enhances our understanding of how Earth’s interior works, shedding light on mantle composition, magma generation, and tectonic plate interactions.
By studying past volcanic events, scientists can reconstruct Earth’s history and gain insights into its long-term evolution.
The Interdisciplinary Nature of Studying Volcanoes:
Volcanology is inherently interdisciplinary, involving fields such as geology, geophysics, geochemistry, climatology, and more.
Volcanic research contributes to various scientific advancements and offers a holistic understanding of Earth’s natural processes.
As we continue to explore the depths of volcanology, it becomes evident that the study of volcanoes is not just about understanding geological phenomena; it’s about comprehending the intricate connections between the Earth’s crust, atmosphere, climate, and human societies. From monitoring volcanic activity to deciphering the clues hidden within volcanic rocks, the pursuit of knowledge in this field unlocks insights that shape our perception of the planet and inform strategies for living in harmony with its dynamic nature.
Earthquakes are natural geological phenomena that occur when there is a sudden release of energy in the Earth’s crust, resulting in seismic waves. These waves cause the ground to shake, often leading to the displacement of the Earth’s surface. Earthquakes can range in size and intensity, from small tremors that go unnoticed to massive quakes that cause widespread devastation.
An earthquake is defined as the shaking of the surface of the Earth resulting from a sudden release of energy in the Earth’s lithosphere that creates seismic waves. This release of energy usually occurs because of the movement of tectonic plates beneath the Earth’s surface. The point on the Earth’s surface directly above the point where the earthquake originates is called the epicenter.
Importance of Understanding Seismic Activity:
Mitigation and Preparedness: Understanding seismic activity is crucial for developing strategies to mitigate the impact of earthquakes. This includes constructing earthquake-resistant buildings and infrastructure, creating early warning systems, and implementing emergency response plans.
Risk Assessment: By studying seismic activity, scientists can assess the level of earthquake risk in different regions. This information is vital for urban planning and land use management to reduce vulnerability and enhance resilience.
Engineering Design: Engineers use knowledge of seismic activity to design structures that can withstand the forces generated by earthquakes. This is particularly important in areas prone to seismic activity.
Public Safety: Awareness and education about seismic activity contribute to public safety. People in earthquake-prone areas can be better prepared to respond appropriately during an earthquake, reducing the risk of injuries and fatalities.
Scientific Understanding: Studying earthquakes provides valuable insights into the Earth’s internal structure and the dynamics of tectonic plate movements. This scientific understanding contributes to advancements in geophysics and seismology.
Historical Significance of Earthquakes:
Cultural Impact: Throughout history, earthquakes have played a significant role in shaping cultures and societies. They often find representation in myths, legends, and religious beliefs, reflecting the profound impact these natural events have on human communities.
Historical Events: Earthquakes have been responsible for some of the most devastating events in history. Famous earthquakes, such as the 1906 San Francisco earthquake or the 2010 Haiti earthquake, have left a lasting mark on the affected regions and influenced subsequent developments.
Tectonic Plate Theory: The study of earthquakes has been instrumental in developing the theory of plate tectonics, which explains the movement and interaction of the Earth’s lithospheric plates. This theory has revolutionized our understanding of Earth’s geological processes.
In conclusion, understanding seismic activity is essential for both practical and scientific reasons. It not only helps mitigate the impact of earthquakes on human societies but also contributes to our broader understanding of the Earth’s dynamic processes.
The Earth’s lithosphere is divided into several rigid plates that float on the semi-fluid asthenosphere beneath them.
Plate boundaries are the areas where these plates interact, and seismic activity is often concentrated along these boundaries.
There are three main types of plate boundaries: divergent boundaries, convergent boundaries, and transform boundaries.
Subduction Zones, Transform Faults, and Divergent Boundaries:
Subduction Zones: Occur where one tectonic plate is forced beneath another. This process often leads to intense seismic activity and the formation of deep ocean trenches.
Transform Faults: Marked by horizontal motion between two plates sliding past each other. Earthquakes along transform faults are common, such as along the San Andreas Fault in California.
Divergent Boundaries: Characterized by plates moving away from each other, often occurring along mid-ocean ridges. As plates separate, magma rises from below, creating new crust and causing earthquakes.
Seismic Waves:
Seismic Waves
P-waves and S-waves:
P-waves (Primary or Compressional Waves): These are the fastest seismic waves and travel through solids, liquids, and gases. They cause particles to move in the same direction as the wave.
S-waves (Secondary or Shear Waves): These waves are slower than P-waves and only travel through solids. They cause particles to move perpendicular to the direction of the wave.
Surface Waves:
Surface waves are slower than P-waves and S-waves but can cause significant damage. They travel along the Earth’s surface and have both horizontal and vertical motion. Love waves and Rayleigh waves are examples of surface waves.
Faults:
Types of Faults (Normal, Reverse, Strike-Slip)
Types of Faults (Normal, Reverse, Strike-Slip):
Normal Faults: Occur in extensional environments where the Earth’s crust is being pulled apart. The hanging wall moves downward relative to the footwall.
Reverse Faults: Form in compressional environments where the Earth’s crust is being pushed together. The hanging wall moves upward relative to the footwall.
Strike-Slip Faults: Characterized by horizontal motion, where two blocks slide past each other horizontally. The San Andreas Fault is a notable strike-slip fault.
Faulting Mechanisms:
Brittle Deformation: In the shallow crust, rocks tend to fracture and fault in response to stress. This is common in areas where earthquakes occur.
Ductile Deformation: Deeper in the Earth, rocks may deform without significant faulting, exhibiting plastic flow instead of fracturing.
Understanding these fundamental aspects of earthquakes, including plate tectonics, seismic waves, and faults, is crucial for comprehending the geological processes that lead to seismic activity and earthquakes.
Measurement and Detection of Earthquakes
Seismograph device
Seismometers and Seismographs:
How Seismometers Work:
Seismometers, or seismographs, are instruments designed to detect and record the vibrations produced by seismic waves during an earthquake.
The basic components include a mass (pendulum or spring-mounted mass), a frame, and a recording device.
When seismic waves cause the ground to shake, the seismometer’s mass remains relatively stationary due to inertia, while the Earth moves beneath it.
The relative motion between the mass and the Earth is then amplified and recorded, producing a seismogram that represents the earthquake’s characteristics.
Importance of Seismographs in Earthquake Detection:
Seismographs are crucial for monitoring and studying earthquakes, providing valuable data for understanding their magnitude, depth, and epicenter.
They play a central role in earthquake early warning systems, helping to provide advance notice to areas at risk.
Seismographs also contribute to the development of seismic hazard maps, aiding in preparedness and risk mitigation efforts.
Richter Scale and Moment Magnitude Scale:
Richter Scale and Moment Magnitude Scale
Comparison and Limitations:
Richter Scale: Developed by Charles F. Richter, it measures the amplitude of seismic waves. However, it is limited in accurately assessing larger earthquakes and is now less commonly used.
Moment Magnitude Scale (Mw): The Moment Magnitude Scale is currently favored for assessing earthquake magnitude. It considers the total energy released, fault length, and average slip along the fault. It provides a more accurate representation of an earthquake’s size, especially for larger events.
Advances in Magnitude Measurement:
The Moment Magnitude Scale has become the standard for measuring earthquake magnitude due to its broader applicability across a wide range of earthquake sizes.
Advances in technology, including the use of modern seismometers and sophisticated data analysis techniques, have improved the accuracy and precision of magnitude determinations.
Moment magnitude is preferred for assessing the size of very large earthquakes because it provides a more reliable and consistent measure.
Understanding seismic measurement and detection is essential for accurately assessing and responding to earthquake activity. Modern techniques and advancements in technology contribute to more precise measurements and a better understanding of earthquake characteristics.
Earthquake Hazards
Ground Shaking:
Intensity and Amplification:
Intensity: The level of ground shaking at a specific location during an earthquake is known as intensity. It is measured on the Modified Mercalli Intensity (MMI) scale, which ranges from I (not felt) to XII (total destruction).
Amplification: Ground shaking can be amplified in certain geological conditions, such as soft soils. This amplification can lead to more significant damage to structures built on these types of soils.
Factors Influencing Ground Shaking:
Distance from the Epicenter: Ground shaking is typically more intense closer to the earthquake’s epicenter.
Depth of the Earthquake: Shallow earthquakes may result in stronger ground shaking than deeper ones.
Geological Conditions: The type of soil and geological formations can influence the amplitude and duration of ground shaking.
Surface Rupture:
Crack of asphalt road after earthquake
Effects on Infrastructure:
Displacement of Structures: Surface rupture can displace the ground horizontally and vertically, causing damage to buildings, roads, and other infrastructure.
Direct Impact: Structures intersecting the fault line may experience direct rupture-related damage.
Mitigation Strategies:
Land-use Planning: Avoiding construction directly on active fault lines through proper land-use planning.
Engineering Solutions: Designing structures with flexible building materials and construction techniques that can accommodate ground movement.
Seismic Retrofitting: Strengthening existing structures to make them more resistant to earthquake forces.
Secondary Hazards:
Tsunamis:
Formation: Tsunamis are often generated by undersea earthquakes, particularly those associated with subduction zones. The vertical displacement of the seafloor displaces water, creating a series of powerful waves.
Effects: Tsunamis can cause devastating coastal flooding and impact communities far from the earthquake’s epicenter.
Triggering Mechanisms: Earthquakes can trigger landslides by shaking loose rocks and soil on steep slopes.
Impact: Landslides can bury structures, block roads, and lead to further destruction.
Mitigation Strategies for Secondary Hazards:
Early Warning Systems: Implementing early warning systems for tsunamis to provide coastal communities with advance notice.
Vegetation and Slope Stability: Maintaining vegetation on slopes to stabilize soil and reduce the risk of landslides.
Infrastructure Planning: Avoiding critical infrastructure in high-risk areas and implementing measures to reinforce vulnerable structures.
Understanding and mitigating these earthquake hazards are crucial for minimizing the impact of seismic events on communities and infrastructure. This involves a combination of scientific research, engineering solutions, and effective land-use planning.
Earthquake Preparedness and Prediction
Early Warning Systems:
Success Stories:
Japan: Japan has a well-established earthquake early warning system that utilizes a network of seismometers. The system provides alerts seconds to minutes before strong shaking begins, allowing for actions like automatic braking on trains, shutdown of industrial processes, and alerts to the general public.
Mexico: Mexico has implemented the Earthquake Early Warning System (SASMEX), which has been successful in providing warnings to the public, schools, and businesses, helping reduce casualties and damage.
Challenges and Limitations:
Limited Warning Time: Early warning systems provide only a brief advance notice, ranging from a few seconds to a couple of minutes, depending on the distance from the earthquake’s epicenter.
False Alarms: The challenge of minimizing false alarms while ensuring timely and accurate warnings poses a significant technical challenge.
Infrastructure: The effectiveness of early warning systems depends on robust infrastructure, including real-time communication networks, which may be lacking in some regions.
Building Codes and Seismic Design:
Retrofitting:
Definition: Retrofitting involves modifying existing buildings and infrastructure to make them more resistant to seismic forces.
Importance: Retrofitting is crucial for enhancing the earthquake resilience of older structures that may not meet current seismic design standards.
Methods: Techniques include adding braces, base isolators, and dampers to absorb and dissipate seismic energy.
Impact on Infrastructure:
Building Codes: Implementing and enforcing stringent building codes is essential for new construction to ensure that structures are designed to withstand seismic forces.
Infrastructure Resilience: Seismic design considerations extend beyond buildings to include bridges, dams, and other critical infrastructure. Proper design and construction practices are vital for reducing damage and protecting public safety.
Effective earthquake preparedness and prediction involve a combination of technological, engineering, and regulatory measures. Early warning systems can provide valuable seconds to minutes for people to take protective actions, and building codes play a crucial role in ensuring that structures are resilient to seismic forces. Retrofitting existing structures further contributes to overall community resilience by reducing vulnerability to earthquakes. Ongoing research and investment in these areas are essential for improving earthquake resilience globally.
Notable Earthquakes
Indian Ocean Earthquake (2012)
Great East Japan Earthquake (2011): A massive magnitude 9.0 earthquake struck off the northeastern coast of Japan, triggering a powerful tsunami. The disaster resulted in significant loss of life, damage to infrastructure, and the Fukushima Daiichi nuclear disaster.
Sumatra-Andaman Earthquake (2004): With a magnitude of 9.1–9.3, this earthquake triggered a devastating tsunami across the Indian Ocean on December 26, 2004. It affected multiple countries and caused widespread destruction and loss of life.
Haiti Earthquake (2010): A magnitude 7.0 earthquake struck near Port-au-Prince, the capital of Haiti, causing extensive damage and resulting in a humanitarian crisis. The earthquake’s impact was exacerbated by the country’s vulnerable infrastructure.
San Francisco Earthquake (1906): The magnitude 7.8 earthquake and subsequent fires devastated San Francisco on April 18, 1906. It remains one of the most significant earthquakes in the history of the United States, leading to major changes in earthquake preparedness and building practices.
Indian Ocean Earthquake (2012): A magnitude 8.6 earthquake occurred off the west coast of northern Sumatra. Although it did not cause significant damage, it raised concerns about the potential for larger earthquakes in the region.
For the latest information on recent earthquakes, please refer to reliable earthquake monitoring websites or local geological agencies.
Case Studies
New Madrid Seismic Zone:
New Madrid Seismic Zone
Geological Features:
The New Madrid Seismic Zone (NMSZ) is located in the central United States, primarily in the states of Missouri, Arkansas, Tennessee, and Kentucky.
It is characterized by a series of faults and fractures in the Earth’s crust, with the most notable being the Reelfoot Fault.
The region is situated away from tectonic plate boundaries, making it an intraplate seismic zone. The geology of the area includes old faults that were reactivated due to stresses within the North American Plate.
Historical Seismicity:
The NMSZ gained historical significance due to a series of powerful earthquakes that occurred between December 1811 and February 1812, with estimated magnitudes of 7.5 to 7.9.
These earthquakes caused the Mississippi River to flow backward temporarily, created new landforms such as Reelfoot Lake in Tennessee, and were felt over a vast area, including the eastern United States.
While seismic activity in the NMSZ has been relatively low in recent decades, it remains a focus of scientific study and earthquake preparedness efforts due to the potential for significant future seismic events.
Ring of Fire:
Ring of Fire
Pacific Rim Tectonics:
The Ring of Fire is a horseshoe-shaped zone around the Pacific Ocean basin that is characterized by high seismic and volcanic activity.
It is associated with the boundaries of several tectonic plates, including the Pacific Plate, North American Plate, South American Plate, Juan de Fuca Plate, Philippine Sea Plate, and others.
Subduction zones are prevalent in the Ring of Fire, where one tectonic plate is forced beneath another. This process leads to the formation of deep ocean trenches, volcanic arcs, and seismic activity.
Seismic Hotspots:
The Ring of Fire includes numerous seismic hotspots, regions where magma rises from the mantle to the Earth’s crust, leading to volcanic activity and seismicity.
Notable volcanic arcs and hotspots along the Ring of Fire include the Andes in South America, the Cascade Range in the Pacific Northwest, the Aleutian Islands in Alaska, and the Japanese archipelago.
The region is known for its frequent earthquakes and powerful volcanic eruptions, making it one of the most geologically dynamic and hazardous areas on Earth.
These case studies highlight the geological features and historical seismicity of two significant seismic zones—New Madrid Seismic Zone in the central United States and the Ring of Fire along the Pacific Rim. Understanding these regions is crucial for earthquake preparedness and risk mitigation efforts.
Conclusion
In conclusion, the study of earthquakes encompasses a range of interconnected factors, from the geological processes underlying seismic activity to the impacts on human societies and infrastructure. Here is a recap of key points discussed:
Basics of Earthquakes:
Earthquakes result from the release of energy in the Earth’s crust, often associated with tectonic plate movements.
Plate tectonics, seismic waves (P-waves, S-waves, surface waves), and faults are fundamental components of earthquake dynamics.
Earthquake Hazards:
Ground shaking, surface rupture, and secondary hazards such as tsunamis and landslides pose significant threats during earthquakes.
Mitigation strategies include early warning systems, building codes, seismic design, and retrofitting.
Measurement and Detection:
Seismometers and seismographs play a crucial role in detecting and recording seismic waves.
The Richter Scale has been largely replaced by the Moment Magnitude Scale for more accurate magnitude measurements.
Notable Earthquakes:
Historical earthquakes, such as the Great East Japan Earthquake and the Indian Ocean Earthquake, have had profound impacts on communities and shaped seismic research and preparedness.
Case Studies:
The New Madrid Seismic Zone in the central U.S. and the Ring of Fire along the Pacific Rim exemplify different seismic settings with unique geological features and historical seismicity.
Earthquake Preparedness and Prediction:
Early warning systems provide critical seconds to minutes for protective actions.
Building codes, seismic design, and retrofitting are essential for enhancing the resilience of structures and infrastructure.
Importance of Continued Research and Preparedness:
Ongoing research is vital for improving our understanding of seismic processes and developing more effective mitigation strategies.
Preparedness measures at individual, community, and governmental levels are crucial for reducing the impact of earthquakes on human lives and property.
Encouraging Public Awareness and Education:
Public awareness and education initiatives are essential for fostering a culture of preparedness.
Understanding earthquake risks, knowing how to respond during an earthquake, and participating in drills contribute to community resilience.
Continued collaboration between scientists, engineers, policymakers, and the public is essential for building a safer and more resilient future in the face of earthquake hazards. By integrating knowledge, preparedness measures, and public awareness, we can mitigate the impact of earthquakes and enhance the safety of communities worldwide.
The process through which water is transferred from the surface of the
Earth (land surface, free water surfaces, soil water, etc.) to the atmosphere
is called evaporation.During evaporation process the latent heat of evaporation is taken from the surface of evaporation.Therefore evaporation is considered as a cooling process. Evaporation from land surface, free water surfaces, soil water, etc. are of great importance in hydrological and meterological studies,
because it affects:
the capacity of reservoirs,
the yield of river basins,
the size of pumping plants,
the consumptive use of water by plants, etc.
Transpiration defines the water loss from plants to atmosphere through the pores at the surface of their leaves.
The water returns to the atmospherein vapor form,
not via a single mechanism, but through three distinct processes.
the first process involves the fraction of water
intercepted by vegetation before
reaching the ground,
the second is the transpiration of plants,
and the third is the evaporation of
gravitational water.
water cycle
A portion of the precipitation falling on the vegetation covered land may be retained by plants. This portion is called interception.
This portion generally evaporates back to the atmosphere without reaching the ground surface.A very small amount of the water retained on the plants falls on the ground from the leaves. This portion is named as throughfall.
In the vegetation covered areas it is almost impossible to differentiate between evaporation and transpiration.Therefore, the two processes are lumped together and referred to as evapotranspiration.
Evaporation begins with the
movement of molecules of water.Inside a mass of liquid water, the
molecules vibrate and circulate in random fashion.This movement is related to the temperature: the higher the temperature, the more the movement is amplified.
The rate of evaporation
and evapotranspiration vary depending on:
meteorological (atmospheric) factors influencing the region,
and on the nature of the evaporating
surface.
The factors effecting the rate of
evaporation (and also evapotranspiration) are:
Solar radiation
Relative humidity
Air temperature
Wind
Atmospheric pressure
Temperature of the liquid water
Salinity
Depth of water
Aerodynamic characteristics
Energy characteristics
Solar radiation
Solar radiation is a driving force of
weather and climatic conditions, and consequently, of the hydrological cycle.Solar radiation supplies the energy necessary for the liquid water
molecules to evaporate.
Solar
radiation affects
the atmosphere,
the hydrosphere
and the lithosphere
At the time of evaporation, thermal energy (i.e. sensible heat) is transferred into latent energy.Latent heat (energy) is the heat either absorbed or released during a phase change from ice to liquid water, or liquid water to water vapour.When water moves from liquid to gas this is a negative flux (i.e. energy is absorbed). During the opposite phase change (gas to liquid) positive heat flux occures (i.e. energy is released).
Relative humidity
For a certain temperature
and air pressureit is possible to
specify the maximum amount of water vapour that may be held by the parcel of
air.
The saturation deficit is the difference between the saturation vapor pressure eS and the actual vapor pressure ea.
This deficit (es-ea) can also be described in relation to the concept of relative humidity Hr, Hr = (ea / es). 100
Relative humidity is the relationship between the quantity of water contained in an air mass and the maximum quantity of water the air mass can hold.
Hr = (ea
/ es). 100
The ability of the air to absorb more water vapor decreases as the humidity of air increases, so the rate of evaporation becomes slower.
Air temperature
Temperature is closely linked to the rate of radiation. Radiation itself is correlated directly to evaporation. It follows, then, that there is a relationship between evaporation and the temperature at the evaporating surface. The rate of evaporation is, in particular, a function of increasing temperature.Near the ground, air temperature is heavily
influenced by
the nature of the land surface
and the amount of sunshine.
The total amount of water vapour that may be held by a parcel of air is temperature and pressure dependent.
The temperature of air
has double effect on evaporation:
It increases
saturation vapor pressure, which means
increasing the saturation deficit.
On the other
hand, high temperature implies that there is energy available for evaporation.
Wind
As the liquid water vaporizes from a water body, land surface, or soil, etc.the air adjacent to these environments will become vapor saturated. For the continuation of evaporation, this saturated air should be removed. In other words atmospheric mixing has to occure.
The wind plays an essential role in the evaporation processbecause, it replaces the saturated air next to an evaporating surface with a drier layer of air. The removal of the saturated air (atmospheric mixing) is carried out by the wind.If the wind speed is zerothe parcel of air will not move away from the evaporative surface and will be saturated with water vapour.
In general, a 10% change in the wind speed causes 1-3% change in the evaporation amount when the other meteorological factors are the same.
Atmospheric pressure
Atmospheric pressure, is expressed
in kilopascals (kPa),
in millimeters of mercury (mm Hg)
or in millibars
(mb).
It represents the weight of a column of air per unit of area. An increase in atmospheric pressureprevents the movement of molecules out of water. The rate of evaporation increaseswhen atmospheric pressure decreases .It may be an important factor where there is an elevation difference of more than a few thousand meters.
Temperature of the liquid water
Molecular motion in the water is temperature dependent. When the temperature of the liquid water is high, molecular motion is fast. In this case the number of molecules leaving the water body will also be high, resulting an increase in evaporation.
If the temperature of the evaporating water is high, it can more readily vaporize. Thus evaporation amounts are high in tropical climates and tend to be low in polar regions. Similar contrasts are found between summer and winter evaporation quantities in mid-latitudes.
Salinity
The salinity (total dissolved solids) refers to all ions (cations and anions) dissolved in the water. The salinity of the water adversely affects evaporation. A 1% increase in salt concentration causes a 1% decrease in evaporation. A similar relationship exists with other substances in solution, because the dissolution of any substance brings about a decrease of vapor pressure. This drop in pressure is directly proportional to the concentration of the substance in solution.
Depth of water
The depth of a body of water plays a determining role in its capacity to store energy. The main difference between a shallow waterbody and a deeper one is that the shallow water is more sensitive to seasonal climatic variations. A shallow waterbody will be more sensitive to weather variations depending on the season.Deeper waterbodies, due to their thermal inertia, will have a very different evaporation response.
Aerodynamic characteristics
The
aerodynamic
characteristics of the surface such as
roughness,
texture of
the material on the surface (fine or coarse materials),
or size of the surface
also affect the amount of the evaporation.
Energy characteristics
The
reflection
coefficient (albedo) of the surface defines the energy
characteristics of the surface.If this coefficient (albedo) is high, a larger portion of the incoming radiation will be reflected, and then evaporation will be lower from that surface.
REFERENCES
Prof.Dr. FİKRET KAÇAROĞLU, Lecture Note, Muğla Sıtkı Koçman University
Davie, T., 2008, Fundamentals of Hydrology (Second Ed.). Rutledge, 200 p.
Musy, A., Higy, C., Hydrology. CRC Press, 316 p.
Newson, M., 1994. Hydrology and The River Environment. Oxford Univ. Pres, UK, 221 p.
Raghunath, H.M., 2006, Hydrology (Second Ed.). New Age Int. Publ., New Delhi, 463 p.
Usul, N., Engineering Hydrology. METU Press, Ankara, 404 p.
Precipitation is the release of water from the atmosphere to reach the surface
of the earth.The term ‘precipitation’ covers all forms of water
being released by the atmosphere (snow, hail,sleet and rain).Precipitation is the major input
of water to a river catchment
area.It needs careful assessment in hydrological and hydrogeological studies.
Occurence and Types of Precipitation
The ability of air to hold water vapour is temperature dependent (Davie, 2008): the cooler the air the less water vapour is retained.If a body of warm, moist air is cooled then it will become saturated with water vapour and eventually the water vapour will condense into liquid or solid water (i.e. water or ice droplets).The water will not condense spontaneously.There need to be minute particles present in the
atmosphere, called condensation nuclei.Upon condensation nuclei
the water or ice droplets form.The
water or ice droplets that form on condensation nuclei are normally too small to fall to the surface as precipitation.They need to grow in order
to have enough
mass to overcome uplifting forces within
a cloud.
There are three conditions that need to be met prior to precipitation forming (Davie, 2008):
Cooling of the atmosphere
Condensation of the vapor onto nuclei
Growth of the water or ice droplets
There are three major
types of precipitation:
Convective precipitation
Orographic precipitation
Cyclonic precipitation
Convective precipitation
Heated air
near the ground expands and absorbs
more water moisture.The warm moisture-laden air moves up and gets
condensed due to lower
temperature, thus producing
precipitation.This type
of precipiation is in the form of local whirling thunder storms.
Orographic precipitation
The
mechanical lifting of moist air over mountain barriers,
causes heavy precipitation
on the windward side of the mountain.
Cyclonic precipitation
The uneven heating of the earth surface by the sun results high and low pressure regions.Air masses move from high pressure regions to low pressure regions, and this motion produces precipitation.If warm air replaces colder air, the front is called a warm front. If cold air displaces warm air, its front is called a cold front.
Measurement of Precipitation
The precipitation is usually expressed as a vertical depth of liquid water.Rainfall is measured by millimetres (mm), rather than by volume such as litres or cubic metres.The measurement of precipitation is the depth of water that would accumulate on the surface if all the rain remained where it had fallen. Snowfall may also be expressed as a depth of liquid water.
For hydrological purposes it is most usefully described in water equivalent depth.
Waterequivalent depth is the depth of water
that would be present
if the snow
melted.
For hydrological analysis it is important;
to know how much precipitation has fallen,
and when this occurred.
Precipitation at different locations in the terrain
is recorded using two main types of rain
gauges:
non-recording rain gauges
recording rain gauges.
Non-recording Rain Gauges
The non-recording rain gauge
consists of a funnel
with a circular rim and
a glass bottle as a receiver.
The cylindrical metal casing
is fixed vertically to the masonry foundation with the level rim above
the ground surface.
Non-recording rain gauge (after Raghunath, 2006).
The rain falling into the funnel is collected in the receiver and is measured in a special measuring glass graduated in mm of rainfall. Usually, rainfall measurements are made at 08.00 hr and at 16.00 hr .During
heavy rains, it must be
measured three or four times
in the day.Thus the non-recording rain gauge gives only the total depth of rainfall for the previous 24 hours.
Recording Rain Gauges
A recording type rain gauge has an automatic mechanical arrangement consisting of:
a clockwork,
a drum with a graph paper
fixed around it
and a pencil
point, which draws the mass curve of rainfall.
This type of gauge is also
called self-recording, automatic or
integrating rain gauge.
From this rainfall mass curve;
the depth of rainfall
in a given time,
the rate or intensity of rainfall
at any instant
during a storm,
time of onset and cessation of rainfall, can be determined.
There are three types
of recording rain gauges:
Tipping bucket rain gauge
Weighing type rain gauge
Float type rain gauge
Tipping bucket rain gauge
Tipping bucket rain gauge consists of
a cylindrical receiver 30 cm diameter with a funnel inside.
Tipping bucket type rain gauge
Below the funnel there are a pair of tipping buckets.The buckets pivoted such that when one of the bucket. Tipping bucket type rain gauge (after Raghunath, 2006). receives a rainfall of 0.25 mm it tips and empties into a tank below, while the other bucket takes its position and the process is repeated. The tipping of the bucket actuates on electric circuit which causes a pen to move on a chart wrapped round a drum which revolves by a clock mechanism.
Weighing type rain gauge
In weighing type of rain gauge,
when a certain weight of rainfall is collected in a tank, it makes a pen to move on a chart wrapped round a clockdriven drum.
Weighing type rain gauge (after Raghunath, 2006).
The rotation of the drum sets the time scale while the vertical motion of the pen records the cumulative precipitation
Float type rain gauge
In float type rain gauge, as the rain is collected in a float chamber, the float moves up which makes a pen to move on a chart wrapped round a clock driven drum.
Float type rain gauge
When the float chamber fills up, the water siphons out automatically through a siphon tube kept in an interconnected siphon chamber. The weighing and float type rain gauges can store a moderate snow fall which the operator can weigh or melt and record the equivalent depth of rain.The snow can be melted in the gaugeitself (as it gets collected there) by a heating system fitted to it or by placing in the gauge certain chemicals (Calcium Chloride, ethylene glycol, etc).
Areal Mean Precipitation
Point precipitation: It is the precipitation recorded at a single station.
For small areas less than 50 km2, point precipitation may be taken as the average depth over the area. In large areas, a network of precipitation gauge stations (meteorological stations) has to be installed. As the precipitation over a large area is not uniform, the average depth of precipitation over the area has to be determined.Areal mean precipitation is the average precipitation of a large area (basin, plain, region etc.) for a specified time period (year, month etc.).
Areal
mean precipitation is determined by one of the
following three methods:
Arithmetic mean (average) method
The isohyetal method
Thiessen polygon method
Mean precipitation amounts of the precipitation gauge stations for the common (same) time period are used in the application of these methods, because the length of the observation period for each station may be different.
Arithmetic mean (average) method
It is obtained by simply averaging arithmetically the amounts of precipitation at the individual precipitation gauge stations (meteorological stations) in the drainage area.
Pave = ∑ Pi / n (2.1)
Pave = average depth
of precipitation over the area
∑ Pi
= sum of precipitation amounts at individual precipitation gauge stations
n = number of precipitation gauge stations in the area
This method is fast and simple
and yields
good
estimates in flat country
(Raghunath, 2006):
if the gauges are uniformly distributed,
and if the precipitation at different stations
do not vary very widely
from the mean.
The isohyetal method
The isohyetal method
In this method; the precipitations measured at gauging sites (meteorological stations) are plotted on a suitable base map, and the lines of equal recipitation (isohyets) are drawn giving consideration to orographic effects and storm morphology.
An isohyetal map shows lines of equal precipitation drawn the same way a topographic contour map is drawn. An isohyetal map has a precipitation interval between isohyets-10 mm, 25 mm, 50 mm, etc.
The average precipitation between the succesive isohyets (P1, P2, P3,…) are taken as the average of the two isohyetal values.
These averages are; weighted with the areas between the isohyets (a1, a2, a3, …), added up, and divided by the total area of the basin which gives the average depth of precipitation over the entire basin.
Pave = ∑ * (Pi +Pi+1)/2 ] ai
/ A (2.2) ai =
area between the
two
successive isohyets
Pi and
Pi+1
A = total area of the basin.
Thiessen polygon method
This method attempts to allow for non-uniform distribution of gauges by providing a weighting factor for
each gauge (Raghunath, 2006).
The stations are plotted on a base map and
are connected by straight lines.
Thiessen polygon method
Perpendicular bisectors are drawn to the straight
lines, joining adjacent stations
to form polygons.
Each polygon area is assumed
to be influenced by
the precipitation gauge station inside it.
P1, P2, P3, …. are the
precipitations at the individual stations,
and a1, a2, a3, ….
are the areas of the polygons
surrounding these stations (influence
areas).
The average
depth of precipitation for the basin is given by
Pave = ∑ Pi ai
/ A (2.3) A = total area
of the basin.
The results
obtained are usually
more accurate than those obtained by simple
arithmetic averaging.
The gauges (stations) should be properly located over the catchment to get regular shaped polygons.
Evaporation and Transpiration
The process through which water is transferred from the Earth surface (land surface, free water surfaces, soil water, etc.) to the atmosphere is called evaporation. During evaporation process the latent heat of evaporation is taken from the surface of evaporation. Therefore evaporation is considered as a cooling process. Evaporation from land surface, free water
surfaces, soil water, etc. are of great importance in hydrological and meterological studies because
it affects (Usul, 2001):
the capacity of reservoirs,
the yield of river basins,
the size of pumping
plants,
the consumptive use of water by plants, etc.
Transpiration defines the water loss from plants to atmosphere through the pores at the surface of their leaves. In the vegetation covered areas it is almost impossible to differentiate between evaporation and transpiration. Therefore, the two processes are lumped together and referred to as evapotranspiration.
Evaporation
The rate of evaporation and evapotranspiration vary depending on:
meteorological (atmospheric) factors
influencing the region,
and on the nature of the evaporating surface.
The factors effecting the rate of evaporation (and also evapotranspiration) are:
Solar radiation
Relative humidity
Air temperature
Wind
Atmospheric pressure
Temperature of the liquid water
Salinity
Aerodynamic characteristics
Energy characteristics
Measurement of evaporation
The most
common method for the
measurement of evaporation is using
an evaporationpan.
This is a large
pan of water with a water
depth measuring instrument.
Masurement of evaporation
This
device allows to record how much water is lost through
evaporation over a time period.
At a standard meteorological station the evaporation is measured daily as the change in water depth. An evaporation pan is filled with water, hence the open water evaporation is measured. A standard evaporation pan, called a Class A evaporation pan is 122 cm in diameter and 25.4 cm deep.
Empirical coefficients (pan coefficient) are applied to estimate the evaporation from larger water bodies (lake, dam resservoir etc.) using measured pan evaporation.
The values of the pan coefficient for Class A evaporation pan ranges between 0.60-0.80, and 0.70 is used as an annual average.
Evaporation Estimation Methods
The difficulties in measuring evaporation using meteorological instruments has led to much effort being placed on estimating evaporation.
There are different methods to estimate evaporation:
Emperical equations are based
on measured meteorollogical variables (parameters).
Precipitation, solar
radiation, wind speed
and relative humidity values are used in estimation of the evaporation by these equations.
Using these equations it is possible to make good estimation of evaporation from lakes for annual, monthly, or daily periods.
Transpiration
Transpirationby a plant leads to evaporation
from leaves through
small holes (stomata) in the leaf.
This is sometimes referred to as dry leaf evaporation.
Various methods are devised by botanists for the measurement of transpiration. One of the widely used methods is measurement by phytometer (Raghunath, 2006).
A phytometer consists of a closed water tight tank with sufficient soil for plant growth with only the plant exposed.
Water is applied artificially till the plant
growth is complete.
The equipment is weighed in the beginning (W1) and
at the end of the experiment (W2).
Water applied during the growth (w) is measured and the water consumed by transpiration
(Wt) is obtained as
Wt = (W1 + w) – W2
Evapotranspiration
Evapotranspiration (Et) is the total water lost from a cropped (or irrigated) land due to evaporation from the soil and transpiration by the plants.Potential evapotranspiration (Ept) is the evapotranspiration from the short green vegetation when the roots are supplied with unlimited water covering the soil. It is usually expressed as a depth (cm, mm) over the area.
The following are some of the methods of estimating evapotranspiration (Raghunath, 2006):
Tanks and lysimeter experiments
Field experimental plots
Evapotranspiration equations as developed by Lowry-Johnson, Penman, Thornthwaite, Blaney-Criddle, etc.
Evaporation index method.
Infiltration
Water entering the soil at the ground surface is called infiltration. It replenishes the soil moisture deficiency and the excess water moves downward by the force of gravity. This process is called deep seepage or percolation, recharges groundwater and builds up the ground water table.
The maximum rate at which the soil in any given condition is capable of absorbing water is called its infiltration capacity.
Infiltration (f) often begins at a high rate (20 to 25 cm/hr), and decreases to a fairly steady state rate (fc) as the rain continues, called the ultimate fp (=1.25 to 2.0 cm/hr)
The infiltration rate
The infiltration rate (f) at any time
t is given by Horton’s equation
(Raghunath, 2006): f = fc + (fo – fc) e–kt
fo = initial rate of
infiltration capacity
fc = final constant rate of
infiltration at saturation
k = a constant depending primarily upon soil
and vegetation e = base
of the Napierian logarithm
t = time from beginning of the storm
The infiltration depends upon:
the intensity and duration of rainfall,
weather (temperature),
soil characteristics,
vegetal cover,
land use,
initial soil moisture content (initial wetness),
entrapped air in the soil or rock,
and depth of the ground water table.
Determination of the Infiltration
The methods of determining infiltration are:
Infiltrometers
Observation in pits and ponds
Lysimeters
Artificial rain simulators
Hydrograph analysis
REFERENCES
Prof.Dr. FİKRET KAÇAROĞLU, Lecture Note, Muğla Sıtkı Koçman University
Davie, T., 2008, Fundamentals of Hydrology (Second Ed.). Rutledge, 200 p.
Raghunath, H.M., 2006, Hydrology (Second Ed.). New Age Int. Publ., New Delhi, 463 p.
Usul, N., Engineering Hydrology. METU Press, Ankara, 404 p.
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