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GS Paper: GS1-15.Geographical features and their location- Changes in critical geographical features (including water-bodies and ice-caps) and in flora and fauna and the effects of such changes.

  • What is Onset of Monsoon?

    The monsoon is slated to make its earliest arrival in 13 years over Kerala, informs the India Meteorological Department (IMD).

    What does the “Onset of Monsoon” mean?

    • The onset of the monsoon over Kerala marks the beginning of the four-month, June to September southwest monsoon season over India.
    • It brings more than 70 per cent of the country’s annual rainfall.
    • It marks a significant transition in the large-scale atmospheric and ocean circulations in the Indo-Pacific region.
    • The IMD announces it only after certain newly defined and measurable parameters, adopted in 2016, are met.
    • The onset is a significant day in India’s economic calendar.

    How does IMD predict the monsoon?

    • Broadly, the IMD checks for the consistency of rainfall over a defined geography, its intensity, and wind speed:
    1. Rainfall: The IMD declares the onset of the monsoon if at least 60% of 14 designated meteorological stations in Kerala and Lakshadweep record at least 2.5 mm of rain for two consecutive days at any time after May 10.
    2. Wind field: The depth of westerlies should be upto 600 hectopascal (1 hPa is equal to 1 millibar of pressure) in the area bound by the equator to 10ºN latitude, and from longitude 55ºE to 80ºE. The zonal wind speed over the area bound by 5-10ºN latitude and 70-80ºE longitude should be of the order of 15-20 knots (28-37 kph) at 925 hPa.
    3. Heat: The INSAT-derived Outgoing Longwave Radiation (OLR) value (a measure of the energy emitted to space by the Earth’s surface, oceans, and atmosphere) should be below 200 watt per sq m (wm2) in the box confined by 5-10ºN latitude and 70-75ºE latitude.
    • The onset is not officially declared until the prescribed conditions (above) are met.

    Factors considered by IMD

    • The IMD uses a specialised model that forecasts the arrival dates within a four-day window.
    • It uses six predictors:
    1. Minimum temperatures over northwest India
    2. Pre-monsoon rainfall peak over south Peninsula
    3. Outgoing long-wave radiation (OLR) over the South China Sea
    4. Lower tropospheric zonal wind over the southeast Indian Ocean
    5. Upper tropospheric zonal wind over the east equatorial Indian Ocean, and
    6. OLR over the southwest Pacific region

    Where is the early arrival noticed?

    • The monsoon’s arrival over India is marked by rain over south Andaman Sea, which then advances north-westwards across the Bay of Bengal.
    • In general, the Andaman and Nicobar Islands start receiving monsoon rainfall between May 15 and May 20 every year.
    • And it usually starts raining along the Kerala coast in the last week of May.

    Does an early onset foretell a good monsoon?

    • No, it does not — just as a delay does not foretell a poor monsoon.
    • The onset is just an event that happens during the progress of the monsoon over the Indian subcontinent.
    • A delay of a few days, or perhaps the monsoon arriving a few days early, has no bearing on the quality or amount of rainfall, or its regional distribution across the country.

    Back2Basics: Long Period Average (LPA)

    • The IMD predicts a “normal”, “below normal”, or “above normal” monsoon in relation to a benchmark “long period average” (LPA).
    • The LPA of rainfall is the rainfall recorded over a particular region for a given interval (like month or season) average over a long period like 30 years, 50 years, etc.
    • LPA refers to the average rainfall recorded from June to September for the entire country, the amount of rain that falls every year varies from region to region and from month to month.
    • The IMD’s prediction of a normal monsoon is based on the LPA of the 1971-2020 period, during which India received 87 cm of rain for the entire country on average.
    • It has in the past calculated the LPA at 88 cm for the 1961-2010 period, and at 89 cm for the period 1951-2000.

    Why LPA is needed?

    • The IMD records rainfall data at more than 2,400 locations and 3,500 rain-gauge stations.
    • Because annual rainfall can vary greatly not just from region to region and from month to month, but also from year to year within a particular region or month.
    • An LPA is needed to smooth out trends so that a reasonably accurate prediction can be made.
    • A 50-year LPA covers for large variations in either direction caused by freak years of unusually high or low rainfall, as well as for the periodic drought years.
    • It also takes into account the increasingly common extreme weather events caused by climate change.

    Range of normal rainfall

    The IMD maintains five rainfall distribution categories on an all-India scale. These are:

    1. Normal or near normal, when the percentage departure of actual rainfall is +/-10% of LPA, that is, between 96-104% of LPA;
    2. Below normal, when departure of actual rainfall is less than 10% of LPA, that is 90-96% of LPA;
    3. Above normal, when actual rainfall is 104-110% of LPA;
    4. Deficient, when departure of actual rainfall is less than 90% of LPA; and
    5. Excess, when the departure of actual rainfall is more than 110% of LPA.

    Also read

    Various terms related to Indian Monsoon

     

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  • In news: Tropical Cyclone Asani

    Severe cyclonic storm ‘Asani’, packing winds above 105 kmph and setting off heavy rain, is likely to make landfall on the eastern coast of India.

    What are tropical Cyclones?

    • A tropical cyclone is an intense circular storm that originates over warm tropical oceans and is characterized by low atmospheric pressure, high winds, and heavy rain.
    • Cyclones are formed over slightly warm ocean waters. The temperature of the top layer of the sea, up to a depth of about 60 meters, need to be at least 28°C to support the formation of a cyclone.
    • This explains why the April-May and October-December periods are conducive for cyclones.
    • Then, the low level of air above the waters needs to have an ‘anticlockwise’ rotation (in the northern hemisphere; clockwise in the southern hemisphere).
    • During these periods, there is an ITCZ in the Bay of Bengal whose southern boundary experiences winds from west to east, while the northern boundary has winds flowing east to west.
    • Once formed, cyclones in this area usually move northwest. As it travels over the sea, the cyclone gathers more moist air from the warm sea which adds to its heft.

    Requirements for a Cyclone to form

    There are six main requirements for tropical cyclogenesis:

    • Sufficiently warm sea surface temperatures
    • Atmospheric instability
    • High humidity in the lower to middle levels of the troposphere
    • Enough Coriolis force to develop a low-pressure centre
    • A pre-existing low-level focus or disturbance
    • Low vertical wind shear

    How are the cyclones named?

    • In 2000, a group of nations called WMO/ESCAP (World Meteorological Organisation/United Nations Economic and Social Commission for Asia and the Pacific) decided to name cyclones.
    • It comprised Bangladesh, India, the Maldives, Myanmar, Oman, Pakistan, Sri Lanka and Thailand, decided to start naming cyclones in the region.
    • After each country sent in suggestions, the WMO/ESCAP Panel on Tropical Cyclones (PTC) finalised the list.
    • The WMO/ESCAP expanded to include five more countries in 2018 — Iran, Qatar, Saudi Arabia, United Arab Emirates and Yemen.

    Why is it important to name cyclones?

    • Adopting names for cyclones makes it easier for people to remember, as opposed to numbers and technical terms.
    • It’s easier and less confusing to say “Cyclone Titli” than remember the storm’s number or its longitude and latitude.
    • Apart from the general public, it also helps the scientific community, the media, disaster managers etc.
    • With a name, it is also easy to identify individual cyclones, create awareness of its development, rapidly disseminate warnings to increase community preparedness etc.

     

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  • Places in news: East Timor

    Asia’s youngest nation, East Timor, also known as Timor Leste, holds the second and final round of its presidential election.

    About East Timor

    • The territory was colonized by Portugal in the 18th century and remained under is control until 1975.
    • When the Portuguese withdrew, troops from Indonesia invaded and annexed East Timor as its 27th province.
    • A long and bloody struggle for independence ensued, during which at least 100,000 people died.
    • The East Timorese voted for independence in a 1999 U.N.-supervised referendum, but that unleashed even more violence until peace-keeping forces were allowed to enter.
    • The country was officially recognized by the United Nations in 2002.
    • East Timor has applied to be a member of the Association of Southeast Asian Nations (ASEAN). It currently holds observer status.

    Its geography

    • East Timor comprises the eastern half of Timor Island, the western half of which is part of Indonesia.
    • It spans a 15,000 square km (5,792 square mile) land area – slightly smaller than Israel – and it’s 1.3 million people are predominantly Roman Catholic.

    Politics and economy

    • In nearly 20 years since independence, East Timor’s presidential and parliamentary elections have been dominated by many of the same faces.
    • Its revolutionary have run for and held various positions of power and continue to feature prominently in the running of the country.
    • East Timor depends on revenues from its offshore oil and gas reserves which account for 90% of its gross domestic product.
    • Its main revenue stream, the Bayu Undan gas field, is set to dry up by 2023 and the country is now planning to collaborate with companies like Australia’s Santos to turn it into carbon capture facilities.

     

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  • What is the ‘Long Period Average’, IMD’s benchmark for monsoon prediction?

    India is likely to receive a normal monsoon for the fourth consecutive year, the India Meteorological Department (IMD) said in its first Long Range Forecast (LRF) for this year.

    What is Long Period Average (LPA)?

    • The IMD predicts a “normal”, “below normal”, or “above normal” monsoon in relation to a benchmark “long period average” (LPA).
    • The LPA of rainfall is the rainfall recorded over a particular region for a given interval (like month or season) average over a long period like 30 years, 50 years, etc.
    • LPA refers to the average rainfall recorded from June to September for the entire country, the amount of rain that falls every year varies from region to region and from month to month.
    • The IMD’s prediction of a normal monsoon is based on the LPA of the 1971-2020 period, during which India received 87 cm of rain for the entire country on average.
    • It has in the past calculated the LPA at 88 cm for the 1961-2010 period, and at 89 cm for the period 1951-2000.

    Why LPA is needed?

    • The IMD records rainfall data at more than 2,400 locations and 3,500 rain-gauge stations.
    • Because annual rainfall can vary greatly not just from region to region and from month to month, but also from year to year within a particular region or month.
    • An LPA is needed to smooth out trends so that a reasonably accurate prediction can be made.
    • A 50-year LPA covers for large variations in either direction caused by freak years of unusually high or low rainfall, as well as for the periodic drought years.
    • It also takes into account the increasingly common extreme weather events caused by climate change.

    Range of normal rainfall

    The IMD maintains five rainfall distribution categories on an all-India scale. These are:

    1. Normal or near normal, when the percentage departure of actual rainfall is +/-10% of LPA, that is, between 96-104% of LPA;
    2. Below normal, when departure of actual rainfall is less than 10% of LPA, that is 90-96% of LPA;
    3. Above normal, when actual rainfall is 104-110% of LPA;
    4. Deficient, when departure of actual rainfall is less than 90% of LPA; and
    5. Excess, when the departure of actual rainfall is more than 110% of LPA.

    Also read:

    Various terms related to Indian Monsoon

     

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  • [pib] International Monsoons Project Office (IMPO)

    Union Minister of Science & Technology has launched the International Monsoons Project Office (IMPO).

    International Monsoons Project Office (IMPO)

    • IMPO will be hosted at the Indian Institute of Tropical Meteorology (IITM), Pune, an institution under the Ministry of Earth Sciences, Govt of India, initially for five years.
    • Setting up the IMPO reiterates the importance of monsoons for the national economy.
    • It would encompass activities and connections related to international monsoon research that would be identified and fostered under the leadership of the World Climate Research Programme.
    • Both the World Climate Research Programme and World Weather Research Programme are international programmes coordinated by the United Nations World Meteorological Organisation (WMO).

    Significance of IMPO

    • Setting up the IMPO in India would mean expanding an integrated scientific approach to solve the seasonal variability of monsoons, enhancing the prediction skill of monsoons and cyclones.
    • It would promote knowledge sharing and capacity building in areas of monsoon research crucial for agriculture, water resources and disaster management, hydropower and climate-sensitive socio-economic sectors.
    • It is a step towards making India a global hub for monsoon research and coordination in a seamless manner for addressing common and region-specific aspects of the monsoons around the world.

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    Back2Basics:

    Various terms related to Indian Monsoon

  • Places in news: Erra Matti Dibbalu

    Citizens join hands to preserve the geological marvel of Erra Matti Dibbalu in Visakhapatnam.

    What is Erra Matti Dibbalu?

    • Located between Visakhapatnam and Bheemunipatnam, the Erra Matti Dibbalu are rare red sand dunes that are a reminder of the million years of geological processes.
    • Its towering red sand dunes with patches of greenery is like a meandering maze.
    • The width of the dunes, which runs for five kilometres along the coast, varies from 200 metres to two kilometres.
    • It is listed among the 34 notified National Geological Heritage Monument Sites of India by the Geological Survey of India.

    (Don’t they resemble to Ravines of Chambal?)

    Its formation

    • Studies indicate that the area was tectonically active between 2.5 million years and 11,000 years ago.
    • The sediments are mainly derived from the Khondalite rocks from the hinterland of the Eastern Ghats.
    • Geologically these red sand dune sediments particularly hold significance.
    • They are the result of the combined effect of numerous factors including global climatic changes, sea-level variations, monsoonal variability and as a result serves as valuable paleo-environment indicators.

     

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  • What is Bomb Cyclone?

    Major cities such as New York and Boston in US are witnessing a “Bomb Cyclone” characterized by the explosive power of rapid drops in atmospheric pressure.

    What is Bomb Cyclone?

    • A bomb cyclone is a large, intense mid-latitude storm that has low pressure at its center, weather fronts and an array of associated weather, from blizzards to severe thunderstorms to heavy precipitation.
    • It becomes a bomb when its central pressure decreases very quickly—by at least 24 millibars in 24 hours.
    • When a cyclone “bombs,” or undergoes bombogenesis, this tells us that it has access to the optimal ingredients for strengthening, such as high amounts of heat, moisture and rising air.

    Why is it called a bomb?

    • Most cyclones don’t intensify rapidly in this way.
    • Bomb cyclones put forecasters on high alert, because they can produce significant harmful impacts.

    Its etymology

    • The word “bombogenesis” is a combination of cyclogenesis, which describes the formation of a cyclone or storm, and bomb, which is, well, pretty self-explanatory.
    • This can happen when a cold air mass collides with a warm air mass, such as air over warm ocean waters.
    • The formation of this rapidly strengthening weather system is a process called bombogenesis, which creates what is known as a bomb cyclone.

    How does it occur?

    • Over the warmer ocean, heat and moisture are abundant.
    • But as cool continental air moves overhead and creates a large difference in temperature, the lower atmosphere becomes unstable and buoyant.
    • Air rises, cools and condenses, forming clouds and precipitation.

    Where does it occur the most?

    • The US coast is one of the regions where bombogenesis is most common.
    • That’s because storms in the mid-latitudes – a temperate zone north of the tropics that includes the entire continental US – draw their energy from large temperature contrasts.
    • Along the US East Coast during winter, there’s a naturally potent thermal contrast between the cool land and the warm Gulf Stream current.

     

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  • What is the Pacific ‘Ring of Fire’?

    The Hunga Tonga-Hunga Ha’apai volcano which massively erupted lies along the Pacific ‘Ring of fire’, and is just over 60 kilometers from the island nation of Tonga.

    What is the Pacific ‘Ring of Fire’?

    • The Pacific ‘Ring of Fire’ or Pacific rim, or the Circum-Pacific Belt, is an area along the Pacific Ocean that is characterized by active volcanoes and frequent earthquakes.
    • Volcanic arcs and oceanic trenches partly encircling the Pacific Basin form the so-called Ring of Fire.
    • It is home to about 75 per cent of the world’s volcanoes – more than 450 volcanoes.
    • Also, about 90 per cent of the world’s earthquakes occur here.

    Its spread

    • Its length is over 40,000 kilometres and traces from New Zealand clockwise in an almost circular arc covering Tonga, Kermadec Islands, Indonesia.
    • It is moving up to the Philippines, Japan, and stretching eastward to the Aleutian Islands, then southward along the western coast of North America and South America.

    Seismic activity of the region

    • The area is along several tectonic plates including the Pacific plate, Philippine Plate, Juan de Fuca plate, Cocos plate, Nazca plate, and North American plate.
    • The movement of these plates or tectonic activity makes the area witness abundant earthquakes and tsunamis every year.
    • Along much of the Ring, tectonic plates move towards each other creating subduction zones.
    • One plate gets pushed down or is subducted by the other plate.
    • This is a very slow process – a movement of just one or two inches per year.
    • As this subduction happens, rocks melt, become magma and move to Earth’s surface and cause volcanic activity.

    What has happened in recent eruption in Tonga?

    • In the case of Tonga, the Pacific Plate was pushed down below the Indo-Australian Plate and Tonga plate, causing the molten rock to rise above and form the chain of volcanoes.
    • Subduction zones are also where most of the violent earthquakes on the planet occur.
    • The December 26, 2004 earthquake occurred along the subduction zone where the Indian Plate was subducted beneath the Burma plate.

     

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  • Undersea Volcanic Eruption in Hunga Islands, Tonga

    A distant undersea volcano has erupted in spectacular fashion near the Pacific nation of Tonga sending large tsunami waves reaching the shore.

    Hunga Volcano

    • The Hunga-Tonga-Hunga-Ha’apai volcano has erupted regularly over the past few decades.
    • It consists of two small uninhabited islands, Hunga-Ha’apai and Hunga-Tonga, poking about 100m above sea level 65km north of Tonga’s capital Nuku’alofa.
    • But hiding below the waves is a massive volcano, around 1800m high and 20 kilometres wide.
    • During events in 2009 and 2014/15 hot jets of magma and steam exploded through the waves. But these eruptions were small, dwarfed in scale by the January 2022 events.
    • Researchers suggest this is one of the massive explosions the volcano is capable of producing roughly every thousand years.

    Impact of the eruption

    • The ash plume is already about 20km high.
    • Most remarkably, it spread out almost concentrically over a distance of about 130km from the volcano, creating a plume with a 260km diameter, before it was distorted by the wind.
    • The eruption also produced a tsunami throughout Tonga and neighbouring Fiji and Samoa.
    • Shock waves traversed many thousands of kilometres, were seen from space, and recorded in New Zealand some 2000km away.
    • All these signs suggest the large Hunga caldera has awoken.

    Why is it so explosive even after being underwater?

    Answer: Fuel-coolant interaction

    • If magma rises into sea water slowly, even at temperatures of about 1200 degrees Celsius, a thin film of steam forms between the magma and water.
    • This provides a layer of insulation to allow the outer surface of the magma to cool.
    • But this process doesn’t work when magma is blasted out of the ground full of volcanic gas.
    • When magma enters the water rapidly, any steam layers are quickly disrupted, bringing hot magma in direct contact with cold water.
    • Volcano researchers call this ‘fuel-coolant interaction’ and it is akin to weapons-grade chemical explosions.

    A chain reaction

    • Extremely violent blasts tear the magma apart.
    • A chain reaction begins, with new magma fragments exposing fresh hot interior surfaces to water, and the explosions repeat, ultimately jetting out volcanic particles and causing blasts with supersonic speeds.

    How has it emerged out to be so big?

    • The caldera is a crater-like depression around 5km across.
    • Small eruptions (such as in 2009 and 2014/15) occur mainly at the edge of the caldera, but very big ones come from the caldera itself.
    • These big eruptions are so large the top of the erupting magma collapses inward, deepening the caldera.
    • Looking at the chemistry of past eruptions, we now think the small eruptions represent the magma system slowly recharging itself to prepare for a big event.

    What next?

    • This latest eruption has stepped up the scale in terms of violence.
    • Researchers are still in the middle of this major eruptive sequence and many aspects remain unclear, partly because the island is currently obscured by ash clouds.

     

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  • India’s first open Rock Museum in Hyderabad

    The Ministry of Science & Technology has inaugurated India’s first open rock museum displaying different types of rocks gathered from different States of ages ranging from 3.3 billion years to around 55 million years.

    Rock System in India

    Based on this complex and varied geological history, the Geological Survey of India has classified rock systems of the country into 4 major divisions:

    1. Archaean Rock System
    2. Dravidian Rock System
    3. Purana Rock System
    4. Aryan Rock System

    [I] Archaean Rock System:

    The Archaean group of rocks consists of two systems-(a) Achaean granites and gneisses, and (b) Dharwarian sedimentary:

    Archaean Gneisses and Schists (pre-2500 million years)

    • The Archean System contains the first formed rocks of the earth.
    • The rocks are primarily gneisses and granites, having no marks of fossils.
    • They often underlie the strata formed subsequently and the system is generally known as the basement complex or fundamental gneisses.
    • The Archaean rocks cover two-thirds of peninsular India. They also occur in the roots of the mountain peaks all along the Greater Himalayas, trans-Himalayan ranges of Zaskar, Ladakh and Karakoram.

    Dharwar System (2500-1800 million years ago)

    • The weathering of the Archaean rocks yielded the earliest sediments and formed the oldest sedimentary strata, the Dharwar system.
    • These are found today in metamorphic forms and do not contain fossils.
    • These rocks occur in scattered patches in parts of Karnataka, Tamil Nadu, central and eastern parts of Chotanagpur plateau, Meghalaya plateau, Aravalis, Himalayan region etc

    Mineral contents:

    • They contain gneisses (which range from granite to gabbro) and schists (crystalline rocks such as mica, talc etc.).
    • These rocks have metallic and non-metallic minerals like copper, tin, graphite, lead, zinc, etc.

    [II] Dravidian Rock System:

    • This is also known as carboniferous rock system and formed during the Paleozoic era, i.e., from 600- 300 million years ago.
    • They are not much abundant in India.
    • They have plentiful fossils and beginning of coal formation can be seen in this period. The quality of carboniferous coal is high.
    • They are found in extra- Peninsular regions of the Himalayas and the Gangetic plains.

    Mineral content

    • This type of rock system comprises of limestones, shale and quartzite and Mount Everest is formed of upper Carboniferous limestones.
    • Most of the coal is not of the Carboniferous period, which is found in India.
    • The meaning of Carboniferous in geology is coal-bearing.

    [III] Purana Rock System:

    The Purana rock system has two divisions: Cuddapah system and Vindhyan system. The word ‘Purana’ was used in place of a Proterozoic era in India.

    Cuddapah Rock system:

    • They are observed in Cuddapah districts of Andhra Pradesh.
    • The non-fossiliferous clay, slates, sandstones and limestones were accumulated in the depression between two-fold mountains which is known as synclinal basins.
    • They also have a large accumulation of building purpose cement grade limestones and quartzites.
    • This type of rock contains ore of iron, cobalt, nickel, manganese etc.

    Vindhya Rock System:

    • This type of rock system is also ancient or old sedimentary rocks which are superimposed on the Archaean rock base and derived its name from Vindhya mountains.
    • The recognition of fossils is negligible, only traces of few animal and plant life were found.
    • This rock system has diamond-bearing regions from which Golconda and Panna diamond mined.

    [IV] Aryan Rock System

    The Aryan rock system in India has the following four subsystems:

    1. Gondwana rock system
    2. Jurassic Rock System
    3. Cretaceous system/ Deccan Trap
    4. Tertiary rock system

    (1) Gondwana Rock System:

    • These are found mainly in Raniganj, Jharia regions of Jharkhand, Damodar valley, Pench valley in Chhattisgarh and Madhya Pradesh.
    • They are called so after the name of Gondwana tribe (indigenous people especially residing in Telangana and Andhra Pradesh region).
    • In this type of rock system, you found metallic minerals like iron, manganese, uranium etc. other than coal.
    • They have low carbon content as it is much younger than Carboniferous coal. These rocks have nearly 98% of India’s coal reserve.

    (2) Jurassic Rock System

    • During the latter part of Jurrasic when sea level rises as compared to land and shoreline moves towards ground or land which result in a flood. In geology, this phenomenon is called marine transgression.
    • This gives rise to a thick series of shallow-water deposits kin Rajasthan and Kutch. Between the Guntur and Rajamundry, another transgression in the east coast of Peninsula.
    • In Kuchchh, coral limestone, shales and conglomerates are found.

    (3) Deccan traps

    • These are formed by the flow of magma over the solidified rock system in layers.
    • Deccan trap gets rise due to volcanic outburst over a major area of Peninsular India from the end of Cretaceous till the beginning of Eocene.
    • The meaning of trap is “stair” or “step” in Swedish and called due to deposition of the volcanic outburst which has a flat top and steep sides.
    • It is mainly found in parts of Kuchchh, Saurashtra, Maharashtra, the Malwa plateau and Northern Karnataka and presently cover near 5 lakh sq. Km.
    • Regur, which is black soil, is formed due to the weathering of these rocks for a long time.

    (4) Tertiary rock system

    • The formation of this type of rock system occurs from 60 to 7 million years ago.
    • It is the most noteworthy period in India’s geological history as the Himalayas were born and recent form came in this period.

    Also read:

    The Geological Structure of India

     

     

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