Category: Geography Notes PPT

Andesite is an extrusive volcanic rock. It is an intermediate type between basalt and rhyolite. It is fine-grained in texture and is sodium-rich plagioclase and pyroxene or hornblende. The dominant rock type in island arcs is also known as Andesite. The average composition of the Earth’s crust is andesitic. They are major components of Martian Crust. The name andesite is derived from the Andes mountain range where this rock is found in abundance. 

Andesite Description

A rock that has a medium level of silica and lesser amounts of Alkali metals is Andesite rock. It is also fine-grained. It consists of less than 10% feldspathoid by volume. Andesite is distinguished from basalt by its silica content of over 52%. It is further not possible to determine the mineral composition of volcanic rocks, due to their fine grain-like texture. Andesite is defined chemically as a volcanic rock with a content of 57% to 63% silica. It does not consist of more than 6% alkali metal oxides.

It is usually light to dark grey in color due to its content of pyroxene minerals. It exhibits a wide range of shading. Darker andesite is usually difficult to distinguish from basalt. A common rule of thumb is used, it states when used away from the laboratory, andesite has a color index less than 35.

Porphyritic andesite is another variation that contains larger crystals of plagioclase formed prior to the extrusion in a finer-grained matrix. These minerals have the extreme melting temperatures of the typical minerals that can crystallize from the melting lava. These are usually the first to form solid crystals. Andesite porphyry is the general name that is used for these rocks with two different crystal sizes.

The plagioclase in andesite varies widely in sodium content from anorthite to oligoclase, but it is typically andesine. The mineral included in andesite is augite, pigeonite, or orthopyroxene. 

Andesite Rock 

Andesite rock description or andesite description type falls under the Igneous rock. The lava  that forms Andesite rock has moderate viscosity forming thick lava flow as well as domes. Andesite is the volcanic equivalent of diorite. It contains silica mainly between 52% – 63%. It is used as an aggregate or to fill. Usually used in the construction and roading industries. It is often not ideal for concrete aggregate because of high silica content. 

Above subduction zones are found Andesite and diorite rocks that have continental crusts. They usually form after an oceanic plate melts. The plate melts during its descent. It produces a source of magma. Diorite forms when magma remains below Earth’s surface and cools slowly. Andesite is a fine-grained rock that forms when magma erupts onto the surface and crystallizes quickly. 

Both Andesite and Diorite have a composition that is intermediate between basalt and granite. The parent magmas formed due to partial melting is the reason behind it.  The partial melting is of the basaltic oceanic plate. This magma receives a granitic contribution by melting granitic rocks. They are ascended or mixed with granitic magma.

Andesite Thin Section

A thin section of rock is prepared by gluing a small piece of rock onto a glass slide. It is then ground down to a thickness of 30 microns. It is done so that light shines through it when examined under the microscope. 

Banded iron formation also shortly known as BIF is a major source of iron. BIF is a rock type made up of substituting silica- and iron-rich bands. BIF is economically among the most significant rock types as our society is largely dependent on iron, which is principally extracted from this rock. Photosynthetic organisms that were producing oxygen, but reacted with the iron dissolved in seawater to create iron oxide minerals on the ocean floor, ended creating banded iron formations.

Composition of Banded Iron Formation

Banded iron formation contains layers of iron oxides (essentially either hematite or magnetite) isolated by layers of chert (silica-stocked sedimentary rock). Each layer is generally narrow (millimeters to few centimeters). The rock has a characteristically banded appearance due to differently colored darker iron-rich and lighter silica layers. In some cases BIFs may consist of siderite (carbonate iron-carrying mineral) or pyrite (sulfide) instead of iron oxides and in place of chert the rock may consist of carbonaceous (rich in organic matter) shale.

BIF is a chemogenic sedimentary rock (material thought to be chemically catapulted on the seafloor). Since old age BIFs usually have been metamorphosed to a different degree (particularly older types), but the rock has heavily retained its original appearance since its constituent minerals are reasonably stable at higher temperatures and pressures. These rocks can be defined as metasedimentary chemogenic rocks.

Types of Banded Iron Formation

BIFs formed in three episodes i.e. 3500-3000 Ma (millions of years ago), 2500-2000 Ma, and 1000-500 Ma. The BIFs from these three episodes are known as Algoma-, Superior- and Rapitan-types, respectively. In each case there were several simulations that resulted in their formation.

1. Algoma

Algoma-type is the oldest (from the Archaean) and appears to be linked with volcanic arcs. They are majorly found in old greenstone belts. Iron-rich minerals are customarily magnetite. Algoma-type iron ore bodies are comparatively small, generally less than 100 meters in thickness and several kilometers in lateral extent. Algoma-type accumulations are mined in the Bjørnevatn (Norway), Abitibi greenstone belt (Ontario, Canada), Kostomuksha (Russian Karelia), etc.

2. Superior

So far it is also one of the significant types of banded iron formations formed during the Paleoproterozoic (Superior-type). They formed on firm continental shelves. Superior-type accumulations are in vast dimensions (greater than 100 meters in thickness and over 100 km in lateral extent). A crucial iron-bearing phase is hematite, but magnetite also occurs. Iron mines where BIFs pertains to Superior-type include Lake Superior (Canada, USA), Labrador (Canada), Hamersley Basin (Australia), Kryvyi Rih (Ukraine), and Transvaal Basin (South Africa), Quadrilatero Ferrifero (Brazil), Singhbhum (India).

The ocean was also a profuse source of silica to form chert layers since the seawater is thought to have been saturated with silica (120 mg/l) during most of the Archaean-Proterozoic.

3. Rapitan

This type is the least significant with respect to the volume of ore mined. Their genesis appears to be linked with glaciations, global ice age (Snowball Earth) and related environmental changes. Iron-bearing mineral in Rapitan-type accumulations is hematite1.

The world ocean was almost completely overlaid ice and thus separated from the atmosphere. That reintroduced diminishing conditions in the water column same as those that existed before the oxygenation of the atmosphere. This near global anoxia in seawater is usually perceived to be the reason why BIFs reappeared as iron deposited in the water and were later accumulations when the ice age subsided and the ocean was oxygenated again.

Problem With Banding of BIFs

Another key issue is the banding of BIFs. These bands could display seasonal cycles as modern varves do. Or it could be some other major cyclical alteration in ocean water chemistry or biology. It appears possible that there was some form of biological mediation and the alterations in BIF composition display the cyclical changes in the numbers of organisms.

Fun Facts

• You can spot a 2.1 billion year-old rock with BIF formation at the National Museum of Mineralogy and Geology, Dresden, Germany.

• Approximately a 3-billion-year-old BIF from Canada reveals that the atmosphere and ocean once had no oxygen.

• Various controversies exist over BIF origination, and many theories have been proposed.

• Banded iron formations, although widely mined, remain mysterious in several ways.

• Understanding of their genesis is largely obstructed by the fact that there are no modern analogues.

• As per a theory, BIF formation has been distinguishably ascribed to volcanic activity; rhythmic accumulation from iron and silica solutions because of oxidation, seasonal variations; and precipitation from solution as an outcome of unique oxidation-reduction conditions.

• All these terms (Algoma, Superior, Rapitan) implies localities in Canada, but they are used to classify BIFs worldwide.

Cassiterite which is also known as tinstone is a heavy, metallic hard tin dioxide(SnO₂) that is the major ore of tin. Cassiterite is colorless when it is pure but turns to brown or black when the iron impurities are present. It is generally opaque but is also translucent in thin crystals. Throughout ancient history, cassiterite was the chief tin ore and even to the present day, it remains the most important source of tin. Cassiterite also occurs in granites and pegmatites.In the fifteenth century, the cassiterite veins present in Saxony and Bohemia were mined for tin and the production of tin was at its peak at the same place in the seventeenth century. In the eighteenth century and the nineteenth century, the very large vein deposits of Cornwall were the major source of tin. In the present day, most of the world’s cassiterite has been mined in Indonesia, Bolivia, Malaysia, Nigeria, Myanmar, Thailand, and other major parts of China. In this article on cassiterite, we are going to discuss what is cassiterite, cassiterite ore, its occurrence, and its physical properties.

 

What is Cassiterite? 

Cassiterite name has been derived from the term Cassiterides which in pre-Roman times was applied for ‘islands off the western coast of Europe’.Cassiterite is a tin oxide mineral and it is considered to be the most significant source of tin and most of the world’s supply of tin is derived by mining out cassiterite. Cassiterite chemical composition is SnO₂. Throughout the world, small amounts of primary cassiterite are found in igneous and metamorphic rocks. Cassiterite is also the residual mineral that is found in solid and sediments. It has been shown that cassiterite is more resistant to weathering when compared to other minerals and as a result of this reason, cassiterite in nature is concentrated in the streams and shoreline sediments. Cassiterite is the most important ore of tin and despite that its concentration is high in only a few locations. Cassiterite has been found in the hydrothermal veins and pegmatites which are associated with granite intrusions. 

Occurrence of the Cassiterite Ore 

•  The primary source of cassiterite ore which is worth mining is found in the high-temperature hydrothermal veins that companies granitic intrusions. 

• The alluvial or the placer deposits which contain the resistant weathered grains is considered to be the main source of cassiterite in today’s world. 

• Along with the deposits of cassiterite, there are also deposits of fluorite, topaz, apatite, and tourmaline. 

• The most important deposits of primary cassiterite ore are found in Brazil, Indonesia, Australia, Bolivia, China, England, The Democratic Republic of Congo, Peru, Portugal, Russia, Spain, and other countries of South Asia. 

• The secondary placed deposits are responsible for producing the world’s most cassiterite. These are sediment-hosted concentrations of cassiterite in stream valleys and along the shorelines. 

•  The hardness of cassiterite allows it to survive the stream transport and its property of high specific gravity causes it to concentrate in the deposits that are large and rich enough for mining. 

• The tin mines of Bolivia are the best source of the primary cassiterite, in the tin mines, the cassiterite is found in the hydrothermal veins. Rwanda has a nascent cassiterite mining industry.

• There are also other high specific gravity minerals that occur in the tin deposits. Deposits if cassiterite is being found in Burma, China, Indonesia, Malaysia. Myanmar, Nigeria, and Rwanda.

• There has been fighting over the cassiterite deposits particularly in Walikale and it is considered to be the major cause of the conflict waged in the eastern part of the Democratic Republic of Congo. Due to this reason cassiterite has been considered as the conflict mineral. 

• The United States of America does not have any major deposits of cassiterite or tin minerals and is heavily dependent on other countries for it. There are small deposits in Alaska, South Dakota, and other states.

• In the present day, the major production of tin comes from placer or the alluvial deposits in Malaysia, Thailand, Indonesia, Russia, and the Maakhir region of Somalia.

Physical Characteristics of Cassiterite

• The Colour of cassiterite is black, brownish-black, reddish-brown, brown, red, yellow, gray, white and  it is rarely colorless

• Transparency: Cassiterite is a very transparent mineral and they are transparent in the thin crystals otherwise are opaque. 

• Cassiterite has a luster that is either greasy or adamantine. 

• The crystal structure of cassiterite is tetragonal. 

• Cleavage is good but in two directions which forms prisms but it is poor on the third side(basal).

• Mohs Hardness of cassiterite is between 6-7.

• Specific Gravity of cassiterite mineral is between 6.8-7.1 which is very heavy for nonmetallic minerals.

• Cassiterite mineral has a high refractive index which is approximately close to 2. 

• Diagnostic properties of cassiterite include high specific gravity, bright metallic to adamantine luster, light streak, and fibrous appearance. 

• The chemical composition of cassiterite is SnO₂, Tin oxide. 

• The cassiterite mineral is used as an ore of tin, a collector’s gem, and a mineral specimen.

• The other minerals that are associated with cassiterite are molybdenite, bismuthinite, topaz, fluorite, arsenopyrite, tourmalines, and wolframite.

• The cassiterite mineral is either infusible or soluble with any other compounds. 

• The primary cassiterite ore is found in places such as England; Durango, Mexico; Malaya; Indonesia; Russia,  China, La Paz, and Colquiri areas of Bolivia and Cornwall

Cassiterite – The Gemstone

Cassiterite is a gem that is very rare to be found. Cassiterite must be transparent, free of fractures, have attractive color, and should have a high clarity to be gem-quality cassiterite. When the cassiterite mineral is cut properly it can be a beautiful gemstone. Cassiterite as gemstone occurs in various colors such as yellow, brown, orange, red, and green. Some gemstones of cassiterite have a strong fire that even rivals that of a diamond. 

Cassiterite as the gemstone is not found in the jewelry stores as it is very rare and that is the reason that there is no demand for it. The cassiterite gemstone is so rare that the adequate amounts required to support a marketing campaign are not available and as a result of this cassiterite is cut mainly for collectors and museum exhibits. 

High dispersion is the one property of cassiterite that makes it an eye-catching gemstone. Dispersion is the ability of any material to separate the white light into separate spectral colors. High dispersion is the property that is responsible for producing the colorful “fire” of a diamond. The dispersion of diamond is about 0.044 whereas the dispersion of cassiterite is 0.71 which is considerably higher than that of a diamond. Due to the high dispersion property of cassiterite, it enables it to produce a fire that exceeds that of a diamond. Cassiterite gemstones which have light colors show a strong fire whereas in many cases the cassiterite with dark color partially masks the fire. 

If you have visited the beach, you must have been on the coast. The cost is also known as coastline, or seacoast is defined as the area where the land touches the sea or oceans. The edges of a coast where the land touches water are known as the coastline. The coastline is formed through waves, tides, and currents. 

Coast enables us to understand natural events such as weather or changing sea levels. During storms, coastal areas are the first place to be flooded the most. The coastal areas, as beautiful as they seem to be, become uneven sometimes as they are highly affected by pollution, garbage, oil spills from both land and sea.

Tourists visit the coast during a vacation to participate in different activities like fishing, swimming, and boating. 

What is the Coastal Range?

The coastal range, also known as the Pacific coast range, is the series of mountain ranges in the United States running alongside the Pacific coast for more than 16000 km or 1000 miles starting from west-central Washington in the north to the Transverse Ranges of California in the south. 

The climate of the coastal range is cool, with dry summers and mild, wet winters in the North. From North to South, both summers and winters in the coastal ranges get steadily dusty or dry and variations in wintertime precipitation rise rapidly. Forests along the coast of Northern California and Southern Oregon are influenced by the giant redwoods while farther inland, there can be seen a mixed forest of conifers and broad-leaved redwood. 

Wildlife in the coast range includes small fur-bearing animals such as weavers, rabbits, muskrats, and bobcats, and large animals such as bears, elk, and deer. This is also the place where the legendary hairy, human-like creatures like ‘barefoot’  are almost seen.

Pacific Coast Range

What is Semper Paratus?

The Latin phrase “ Semper Paratus” means “Always Ready”.  Sometimes abbreviated as Semper P.It is also considered to be the official motto of the United States Coast Guard. A 1928 song of the same name, composed in 1927 by Captain Francis Saltan Van Boskerck is also used as the US Coast Guard’s official March and can be seen on the Organization flag.

The origin lyrics of the 1928 song were written by Captain Francis Saltan Van Boskerk in 1922, at the cabin of USRC Yamacraw in Savannah  Georgia. In 1927, he wrote the music on a beat-up old piano in Unalaska, Alaska.

In 1969, the first line of the chorus song was changed from ” So here’s the US Coast Guard Marching Song: We sing on land and sea” to “We are always there for the call, We play our trust in Thee”

What is NVDC?

NVDC, also known as National Vessel  Documentation Centre is the division of the coast guard responsible for managing the certification and federal registration of commercial and recreational boats in the US. The NVDC maintains a database that includes appropriate information regarding every registered ship. The list is available to the public so that they can look for the boats they know or have an interest in. With this, they can find more detailed information about the ships.

 Did You Know

• The climate of the coastal region is the most moderate in the Pacific Northwest.

• The coastal range is the next home to the rainforest.

• If you will measure the total length of the land where it meets water then you will find it is around 312,000 miles or 502,000 km.

• In the countries like Australia or England, the term coast is sometimes referred to as the seaside.

• The most famous example of coast in Great Britain is Holderness coast near Bridlington.

• Coast Guard National Vessel Documentation Centre (NVDC) registered approximately 23000 vessels for commercial and recreational purposes in U.S. waters.

The chemical name of cryolite is sodium hexafluoroaluminate and its chemical formula is Na3AlF6. It’s a rare mineral associated with the once-large deposit at Ivittuut on Greenland’s west coast, which was depleted by 1987. Cryolite, sodium aluminium fluoride, is a colourless to white halide mineral. It’s found in large quantities in Ivigtut, Greenland, and in small amounts in Spain, Colorado, and other places. 

It is used as a solvent for bauxite in the electrolytic production of aluminium and has various other metallurgical applications, and it is used in the glass or ceramic industries and enamel factories, inbounded abrasives as filtering membranes, and in the manufacture of insect-killing chemicals (insecticides). A huge amount of synthetic or artificial cryolite is made from fluorite.

On this page, we have covered all the important topics related to cryolite like cryolite meaning, its uses, properties, and its ore. Let us discuss the cryolite meaning, cryolite meaning indicates that it is a mineral of aluminium and fluoride.

Properties of Cryolite

• Cryolite occurs in a monoclinic crystal state.

• The cryolite is whitish glassy in colour.

• The hardness of cryolite in the moh scale is 2.5 to 3.

• The specific gravity of cryolite is 2.95 to 3.

• Cryolite is transparent to translucent to transparent in nature due to which its refractive index is very low.

• Cryolite is invisible in nature, due to a similar refractive index.

• Cryolite as the essential component of the electrolyte (85 – 90 %) decreases the temperature of the smelting flux electrolysis.

Cryolite Lattice Structure

The above figure represents the cryolite unit cell structure. In the above-shown figure, the arrangement of sodium atoms is shown by the purple colour. Fluorine atoms are shown by pale green colour. Fluorine atoms are arranged in an octahedral form around the sodium metal ion.

What are the Cryolite Ores?

Cryolite is a salt of sodium aluminium hexafluoride. It is represented as Na3AlF6. It consists of Aluminium, Sodium and Fluorine. It can be synthesized by the given reaction.

H2SiF6 + 6 NH3 + 2H20 → 6NH4F + SiO2

6NH4F + 3NaOH + Al(OH)3 → Na3AlF6+ 6NH3 + 6 H2O

Cryolite ores are the chief ore of aluminium. These cryolite ores are associated with the earthy material, these earthy materials are known as gangue.  

Cryolite Uses

• Cyolite plays an important role in the metallurgy of cryolite. It helps in making alumina a good conductor of electricity. 

• It helps in lowering the melting point of alumina.

• Cryolite is used in manufacturing aluminium waste.

• Cryolite is used as a flux in steel aluminization and in welding technology.

• Cryolite is used as additives in abrasives.

• Cryolite is used in the remelting of metals.

What is Synthetic Cryolite?

Synthetic cryolite is a crystalline white powder made of hydrofluoric acid, sodium carbonate, and aluminium. Since it essentially lowers the melting point of alumina, synthetic cryolite is mainly used as a flux in the electrolytic processing of aluminium. Cryolite is used in the ceramic industries and enamel coating industries as a filler, in compounded abrasives as a filler, in the synthesis of sodium salts and aluminium salts, porcelaneous glass, and pesticides and insecticides. Cryolite is a relatively safe insecticide for fruits and vegetables. Many iron, calcium, and magnesium-containing enzymes are inhibited by fluoride.

Types of Synthetic Cryolite

1. Sodium cryolite

2. Potassium cryolite

Let us discuss these synthetic cryolites one by one.

Sodium Cryolite

Sodium Cryolite salts are used as a solvent for bauxite in the electrolytic processing of aluminium; other metallurgical uses include foundry additives for aluminium foundries, sleeves, and cover flux; filler for bonded abrasives in the glass and enamel industries; and insecticide manufacturing.

Potassium Cryolite

Potassium Cryolite (K3AIF6) is utilised for the synthesis of welding agents, blasting agents (a large amount of energy-producing agents), pyrotechnics, and abrasives materials. KAlF4 and K3AlF6 are the chemical formulas for potassium cryolite. Potassium fluoroaluminate, Potassium tetrafluoroaluminate, Potassium Cryolite, Kalium Aluminium Fluoride, KAlF, KAlF4, and K3AlF6 are some of the other names for potassium cryolite.

Extraction of Aluminium Using Cryolite 

The Hall–Héroult process is the most popular industrial smelting method for aluminium. It entails dissolving aluminium oxide (alumina) in molten cryolite aluminium and electrolysing the molten salt bath, usually in a purpose-built cell, which is obtained most often from bauxite, aluminium’s chief ore, via the Bayer process. At 940–980 °C, the Hall–Héroult process produces 99.5–99.8 percent pure aluminium on an industrial scale. Since recycled aluminium does not require electrolysis, it is not used in this process. By emitting carbon dioxide, this process contributes to climate change. 

Sodium cryolite is a key component of the HallHeroult process, which uses an electrolyte to produce aluminium (Na3AlF6). Al2O3 has a very high melting point and is very soluble. Any addition to the molten sodium cryolite (typically AlF3, CaF2, MgF2) lowers the electrolyte liquidus temperature as well as the alumina solubility. Despite this, the operating temperature of aluminium electrolysis remains high (950-960 °C), which is a critical factor in increased fluoride corrosion operation. The inability to use new constructional materials in conventional sodium electrolytes, such as non-consumable anodes, piques interest in finding new low-melted electrolytes.

Did You Know?

• Cryolite is a scarce mineral. It consists of sodium fluoride bonds and aluminium fluoride bonds.

• On immersing it in water, it becomes invisible. Due to its similar refractive properties with water, it becomes invisible, although it does not dissolve.

• Cryolite minerals are found in vast quantities in Greenland.

• Nowadays, cryolite mineral is manufactured artificially from the fluorite.

El Nino and La Nina are opposing phases of the El Nino-Southern Oscillation (ENSO) cycle. The ENSO is a periodic climatic trend that involves temperature fluctuations in the eastern and central tropical Pacific Oceans, as well as changes in upper and lower-level wind patterns, sea level pressure, and tropical rainfall patterns over the Pacific basin. The warm phase of ENSO is typically referred to as El Nino, whereas the cold phase is referred to as La Nina. These deviations from average surface temperatures have the potential to have a substantial impact on global weather and climate conditions. 

This article will help you to understand what the La Nina and El Nino phenomena are and how they affect Indian weather.

El Nino Meaning

In Spanish, El Nino means “small boy” or “Christ child”. As it was initially seen by South American fishermen in the early 17th century, the phenomenon was given this name. Seas tended to become warm in the Pacific Ocean around December, which is why the name was picked. El Nino is a large-scale ocean-atmosphere climatic interaction associated with a recurrent increase of sea surface temperatures in the central and east-central Equatorial Pacific. It is linked to high pressure in the western Pacific. The El Nino effect has a negative influence on the Indian monsoons and, as a result, agriculture in India.

According to the work of Sir Gilbert Walker, climate scientists discovered that El Nino and the Southern Oscillation occur at the same time in the 1930s. A variation in air pressure over the tropical Pacific Ocean is known as the Southern Oscillation. The air pressure over the ocean lowers when coastal waters in the eastern tropical Pacific get warmer (El Nino). El Nino-Southern Oscillation is the name given to these two interconnected occurrences by climatologists (ENSO). The words El Nio and ENSO are now used interchangeably by most subject experts.

El Nino’s Impact on India

The pressure distribution in a typical monsoon year (without El Nino) is as follows.

• The pressure along Peru’s coast in South America is higher than in the region bordering northern Australia and South East Asia. 

• As the Indian Ocean is warmer than the surrounding oceans, it has lower pressure. As a result, moisture-laden winds blow from the western Pacific to the Indian Ocean. 

• As the pressure on India’s landmass is lower than that on the Indian Ocean, moisture-laden winds go farther from the ocean to the lands. The monsoons are disturbed if this typical pressure distribution is disrupted for any cause.

El Nino causes the chilly surface water off the Peruvian coast to warm. The regular trade winds are lost or alter their direction when the ocean is warm. As a result, moisture-laden winds from the western Pacific are steered towards Peru’s coast (the region near northern Australia and South East Asia). It creates significant rainfall in Peru, during the El Nino, depriving the Indian subcontinent of its typical monsoon rains. The greater the temperature and pressure differential, the greater is the rainfall deficit in India.

La Nina Meaning

In Spanish, La Nina means “small girl”, and it is also known as El Viejo, or “cold event”. In the Eastern Pacific, the water temperature drops below average. As a result, a powerful high-pressure system has formed over the eastern equatorial Pacific. Low pressure is now present in the Western Pacific and off the coast of Asia. La Nina causes drought in Peru and Ecuador, major floods in Australia, high temperatures in the Western Pacific, Indian Ocean, and off the coast of Somalia, and abundant monsoon rains in India. La Nina conditions are really advantageous to the Indian monsoon. El Nino and La Nina weather patterns occur every 4–5 years on average. El Nino is more common than La Nina. Typically, the episodes last nine to twelve months.

Effects of El Nino and La Nina on Indian Climate

El Nino generates warm weather across the Indian subcontinent in the winter and dry conditions and a deficient monsoon in the summer. In contrast, La Nina causes a better-than-normal monsoon in India. During the El Nino years of 2002 and 2009, India had little rainfall, although the monsoon was typical during the El Nino years of 1994 and 1997. It signifies that India faced droughts during the monsoon for nearly half of the year due to El Nino in the summer. El Nino will harm crops such as paddy, maize, groundnut, guar, castor, tur, moong, and bajra. 

El Nino: Measuring the Effects

Scientists, governments, and non-governmental organizations (NGOs) use a variety of technology, including scientific buoys, to collect data on the El Nino effect. A buoy is a floating object that serves as a navigational aid or warning signal for ships in the middle of the ocean. They are usually brightly coloured (fluorescent). Temperatures, currents, winds, and humidity are all measured by these buoys. The buoys provide data to academics and forecasters all across the world on a regular basis, allowing scientists to more correctly anticipate El Nino and visualize its evolution and influence around the planet.

The Oceanic Nino Index (ONI) is a tool for determining how much sea surface temperatures have deviated from normal. The major tool for determining, assessing, and forecasting each El Nino event is the Oceanic Nino Index, which is a measure of the departure from normal sea surface temperature in the east-central Pacific Ocean. El Nino occurrences range in severity from mild temperature rises (about 4-5° F) with relatively little local effects on weather and climate to extremely severe increases (14-18° F) linked to global climate change.