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Subject: Geography

  • 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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  • Western Disturbances to bring rain in New Delhi

    Under the influence of two consecutive western disturbances, New Delhi is in for a wet spell.

    Western Disturbances

    • A western disturbance is an extratropical storm originating in the Mediterranean region that brings sudden winter rain to the northwestern parts of the Indian subcontinent.
    • It is a non-monsoonal precipitation pattern driven by the westerlies.
    • The moisture in these storms usually originates over the Mediterranean Sea, the Caspian Sea and the Black Sea.
    • Extratropical storms are global phenomena with moisture usually carried in the upper atmosphere, unlike their tropical counterparts where the moisture is carried in the lower atmosphere.
    • In the case of the Indian subcontinent, moisture is sometimes shed as rain when the storm system encounters the Himalayas.
    • Western disturbances are more frequent and strong in the winter season.

    Impact: Winter Rainfall and Extreme Cold

    • Western disturbances, specifically the ones in winter, bring moderate to heavy rain in low-lying areas and heavy snow to mountainous areas of the Indian Subcontinent.
    • They are the cause of most winter and pre-monsoon season rainfall across northwest India.
    • An average of four to five western disturbances forms during the winter season.

    Its significance

    • Precipitation during the winter season has great importance in agriculture, particularly for the rabi crops.
    • Wheat among them is one of the most important crops, which helps to meet India’s food security.

    Try this PYQ:

    Q. Consider the following statements:

    1. The winds which blow between 30°N and 60°S latitudes throughout the year are known as westerlies.
    2. The moist air masses that cause winter rains in the North-Western region of India are part of westerlies.

    Which of the statements given above is/are correct?

    (a) Only 1

    (b) Only 2

    (c) Both 1 and 2

    (d) Neither 1 nor 2

     

     

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  • Recurring urban floods point to need for moving away from land-centric urbanism

    Context

    Flood in Chennai has revived memories of the devastating Chennai floods of 2015, a collective trauma that its residents are yet to outlive.

    Role of climate change

    • In August this year, as monsoon floods raged across the subcontinent, IPCC’s 6th Assessment Report (AR6) was published.
    • The report noted the increasing frequency of heavy precipitation events since the 1950s and inferred that they were being driven by human-induced climate change.
    • The climate crisis, is here.
    • It has made extreme rainfall events more severe and unpredictable than ever before.

    Role of poor planning and encroachment

    • In 2015, the National Green Tribunal in India formed a committee to report on the status of natural stormwater drains in Delhi.
    • On inspection, out of the 201 “drains” recorded in 1976, 44 were found to be “missing.
    • Geospatial imaging established that 376 km of natural storm drains — encroached on and paved over — had disappeared from Bengaluru.
    • In both cases, these “missing” waterways were either encroached and built over or connected to sewage drains.
    • Poor design and corruption significantly contribute to urban floods.
    • By violating environmental laws and municipal bye-laws, open spaces, wetlands and floodplains have been mercilessly built over, making cities impermeable and hostile to rainwater.

    Way forward

    • We need to move away from land-centric urbanisation and recognise cities as waterscapes.
    • We need to let urban rivers breathe by returning them to their floodplains.
    • The entire urban watershed needs to heal, and for that to happen, we need less concrete and more democracy and science at the grassroots.

    Conclusion

    Ever since concretisation became shorthand for urbanisation, rainfall in a changing climate no longer finds its way towards subterranean capillaries or surface water bodies.

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  • Earth’s first landmass emerged in Singhbhum: Study

    A new study has challenged the widely accepted view that the continents rose from the oceans about 2.5 billion years ago.

    About Singhbhum

    • Singhbhum district of Jharkhand is part of the Chhota Nagpur Division.
    • It is one of the leading producers of copper in India.

    First landmass to emerge

    • The study suggests that the earliest continental landmass to emerge may have been Jharkhand’s Singhbhum region.
    • Scientists have found sandstones in Singhbhum with geological signatures of ancient river channels, tidal plains and beaches over 3.2 billion years old.
    • They somewhat represent the earliest crust exposed to air.

    Studying the sandstones

    • The research studies a sedimentary rock, called granite. They tried to find their age and in which conditions they have formed.
    • They found the age by analysing the uranium and lead contents of tiny minerals.
    • These rocks are 3.1 billion years old, and were formed in ancient rivers, beaches, and shallow seas.
    • All these water bodies could have only existed if there was continental land.
    • Thus, they inferred that the Singhbhum region was above the ocean before 3.1 billion years ago.

    How did they analyse?

    • The researchers studied the granites that form the continental crust of Singhbhum region.
    • These granites are 3.5 to 3.1 billion years old and formed through extensive volcanism that happened about 35-45 km deep inside the Earth.
    • This process continued on-and-off for hundreds of millions of years until all the magma solidified to form a thick continental crust in the area.
    • Due to the thickness and less density, the continental crust emerged above surrounding oceanic crust owing to buoyancy.

    Back2Basics: Emergence of Landmass

    • In the beginning, more than 4.6-billion years ago, the world was a ball of burning gas, spinning through space.
    • It took hundreds of millions of years for the first land masses to emerge.
    • About 250-million years ago, long, long after the Earth had formed, all the continents of the time had joined together to form a super-continent called Pangaea.
    • This super-continent broke up about 200-million years ago to form two giant continents, Gondwana and Laurasia.
    • Gondwana comprised what is now Africa, South America, Australia, Antarctica and India.
    • The Indian sub-continent lay off the east coast of Africa, before it broke off and moved north rapidly.

    Isostacy

    • Huge plates of crustal and upper mantle material (lithosphere) “float” on more dense, plastically flowing rocks of the asthenosphere.
    • The “depth” to which a plate, or block of crust, sinks is a function of its weight and varies as the weight changes.
    • This equilibrium, or balance, between blocks of crust and the underlying mantle is called isostasy.
    • The taller a block of crust is, the deeper it penetrates into the mantle because of its greater mass and weight. Isostasy occurs when each block settles into an equilibrium with the underlying mantle.
    • Blocks of crust that are separated by faults will “settle” at different elevations according to their relative mass.

     

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  • Sixth Mass Extinction?

    A paper published recently has come up with a new reason behind the first mass extinction, also known as the Late Ordovician mass extinction.

    Species Extinction

    • Extinction is a part of life, and animals and plants disappear all the time. About 98% of all the organisms that have ever existed on our planet are now extinct.
    • When a species goes extinct, its role in the ecosystem is usually filled by new species, or other existing ones.

    What is Mass Extinction?

    • Earth’s ‘normal’ extinction rate is often thought to be somewhere between 0.1 and 1 species per 10,000 species per 100 years.
    • This is known as the background rate of extinction.
    • A mass extinction event is when species vanish much faster than they are replaced.
    • This is usually defined as about 75% of the world’s species being lost in a ‘short’ amount of geological time – less than 2.8 million years.

    How many mass extinctions have there been?

    Five great mass extinctions have changed the face of life on Earth. We know what caused some of them, but others remain a mystery:

    [I] Ordovician-Silurian ME

    • It occurred 443 million years ago and wiped out approximately 85% of all species.
    • Scientists think it was caused by temperatures plummeting and huge glaciers forming, which caused sea levels to drop dramatically.
    • This was followed by a period of rapid warming. Many small marine creatures died out.

    [II] Devonian ME

    • It took place 374 million years ago and killed about three-quarters of the world’s species, most of which were marine invertebrates that lived at the bottom of the sea.
    • This was a period of many environmental changes, including global warming and cooling, a rise and fall of sea levels and a reduction in oxygen and carbon dioxide in the atmosphere.
    • We don’t know exactly what triggered the extinction event.

    [III] Permian ME

    • It happened 250 million years ago, was the largest and most devastating event of the five.
    • Also known as the Great Dying, it eradicated more than 95% of all species, including most of the vertebrates which had begun to evolve by this time.
    • Some scientists think Earth was hit by a large asteroid which filled the air with dust particles that blocked out the Sun and caused acid rain.
    • Others think there was a large volcanic explosion that increased carbon dioxide and made the oceans toxic.

    [IV] Triassic ME

    • It took place 200 million years ago, eliminating about 80% of Earth’s species, including many types of dinosaurs.
    • This was probably caused by colossal geological activity that increased carbon dioxide levels and global temperatures, as well as ocean acidification.

    [V] Cretaceous ME

    • It occurred 65 million years ago, killing 78% of all species, including the remaining non-avian dinosaurs.
    • This was most likely caused by an asteroid hitting the Earth in what is now Mexico, potentially compounded by ongoing flood volcanism in what is now India.

    What caused first ME?

    • The cooling climate likely changed the ocean circulation pattern.
    • This caused a disruption in the flow of oxygen-rich water from the shallow seas to deeper oceans, leading to a mass extinction of marine creatures.
    • Ordovician Sea has familiar groups like clams and snails and sponges.
    • Many other groups are now very reduced in diversity or entirely extinct like trilobites, brachiopods, and crinoids.

    The sixth mass extinction

    • We are currently experiencing a sixth mass extinction as the result of human-induced climate change.
    • There have been several theories behind each mass extinction and with advances in new technologies, researchers have been uncovering more intricate details about these events.

    Try this PYQ from CSP 2018

    The term “sixth mass extinction/sixth extinction” is often mentioned in the news in the context of the discussion of:

     

    (a) Widespread monoculture Practices agriculture and large-scale commercial farming with indiscriminate use of chemicals in many parts of the world that may result in the loss of good native ecosystems.

    (b) Fears of a possible collision of a meteorite with the Earth in the near future in the manner it happened 65million years ago that caused the mass extinction of many species including those of dinosaurs.

    (c) Large scale cultivation of genetically modified crops in many parts of the world and promoting their cultivation in other Parts of the world may cause the disappearance of good native crop plants and the loss of food biodiversity.

    (d) Mankind’s over-exploitation/misuse of natural resources, fragmentation/loss, natural habitats, destruction of ecosystems, pollution and global climate change.

     

    [wpdiscuz-feedback id=”agqt1mog92″ question=”Please leave a feedback on this” opened=”1″]Post your answers here.[/wpdiscuz-feedback]

     

     

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  • Various terms related to Indian Monsoon

    The monsoon is likely to begin withdrawing from the mainland from October 6, said the India Meteorological Department (IMD).

    Let us learn all terminologies related to Monsoon.

    What is Monsoon?

    • Indian monsoon, the most prominent of the world’s monsoon systems, which primarily affects India and its surrounding water bodies.
    • It blows from the northeast during cooler months and reverses direction to blow from the southwest during the warmest months of the year.

    Onset of Monsoon

    • This process brings large amounts of rainfall to the region during June and July.
    • As the high-sun season (that is, the Northern Hemisphere summer) moves northward during April, India becomes particularly prone to rapid heating because the highlands to the north protect it from any incursions of cold air.
    • There are three distinct areas of relative upper tropospheric warmth—namely, (1) above the southern Bay of Bengal, (2) above the Plateau of Tibet, and (3) across the trunks of the various peninsulas that are relatively dry during this time.
    • These three areas combine to form a vast heat-source region.
    • In contrast, a heat sink appears over the southern Indian Ocean as the relatively cloud-free air cools by emitting long-wavelength radiation.
    • Monsoon winds at the surface blow from heat sink to heat source.

    Peak period

    • The position of the easterly jet controls the location of monsoonal rains, which occur ahead and to the left of the strongest winds and also behind them and to the right.
    • The surface flow, however, is a strong, south-westerly, humid, and unstable wind that brings humidifies of more than 80 percent and heavy squally showers that are the “burst” of the monsoon.
    • The overall pattern of the advance follows a frontal alignment, but local episodes may differ considerably.

    Key areas

    • Most spectacular clouds and rain occur against the Western Ghats in India, where the early monsoonal airstream piles up against the steep slopes, then recedes, and piles up again to a greater height.
    • Each time it pushes thicker clouds upward until wind and clouds roll over the barrier and, after a few brief spells of absorption by the dry inland air, cascade toward the interior.
    • Various factors, especially topography, combine to make up a complex regional pattern.

    Break in Monsoon

    • During the south-west monsoon period after having rains for a few days, if rain fails to occur for one or more weeks, it is known as break in the monsoon.
    • These dry spells are quite common during the rainy season.
    • In northern India rains are likely to fail if the rain-bearing storms are not very frequent along the monsoon trough or the ITCZ over this region.
    • Over the west coast the dry spells are associated with days when winds blow parallel to the coast.

    Withdrawal of Monsoon

    • By August the intensity and duration of sunshine have decreased, temperatures begin to fall, and the surge of south-westerly air diminishes spasmodically almost to a standstill in the northwest.
    • In September, dry, cool, northerly air begins to circle the west side of the highlands and spread over north-western India.
    • The easterly jet weakens, and the upper tropospheric easterlies move much farther south.
    • Because the moist southwesterlies at lower levels are much weaker and variable, they are soon pushed back.
    • The rainfall becomes extremely variable over most of the region, but showers are still frequent in the south-eastern areas and over the Bay of Bengal.
    • By early October, variable winds are very frequent everywhere.

    Winter rains

    • At the end of the month, the entire Indian region is covered by northerly air and the winter monsoon takes shape.
    • The surface flow is deflected by the Coriolis force and becomes a north-easterly flow.
    • Tropical depressions and cyclones are important contributing factors.
    • Most of India thus begins a sunny, dry, and dusty season.
    • Conversely, the western slopes of the Karakoram Range and Himalayas are then reached by the midlatitude frontal depressions that come from the Atlantic and the Mediterranean.
    • The winter rains they receive, moderate as they are, place them clearly outside the monsoonal realm.

     

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  • Cyclone Gulab

    As a very rare occasion during monsoons, Cyclone Gulab has been developed in the Bay of Bengal and later made landfall close in Andhra Pradesh.

    Tauktae, Amphan, Fani, Titli, Bulbul, Gaja
 And now Gulab. As and when cyclones with intriguing names approach the Indian coasts, a common question comes to our minds: Who names these storms?

     

    This time it is Pakistan, not India, who proposed this name Gulaab!

    About Tropical Cyclones

    • A tropical cyclone is a rapidly rotating storm system characterized by a low-pressure centre, a closed low-level atmospheric circulation, strong winds, and a spiral arrangement of thunderstorms that produce heavy rains.
    • Depending on its location and strength, a tropical cyclone is referred to by different names, including hurricane, typhoon, tropical storm, cyclonic storm, tropical depression, or simply cyclone.
    • A hurricane is a tropical cyclone that occurs in the Atlantic Ocean and the northeastern Pacific Ocean, and a typhoon occurs in the north-western Pacific Ocean.
    • In the south Pacific or the Indian Ocean, comparable storms are referred to simply as “tropical cyclones” or “severe cyclonic storms”.

    Cyclone Gulab

    • Three factors —in-sync phase of Madden Julian Oscillation (MJO), warm sea surface temperatures over the Bay of Bengal, and the formation of a low-pressure system.
    • The system’s intensification phases between low pressure – well-marked low pressure – depression – deep depression and to finally becoming Cyclone Gulab was rather rapid, even as the system moved closer to the south Odisha – north Andhra Pradesh coast, where it also made landfall.

    What makes Gulab special?

    • India has a bi-annual cyclone season that occurs between March to May and October to December. But on rare occasions, cyclones do occur in June and September months.
    • Cyclones are less common during the June to September monsoon season, as there are limited or almost no favourable conditions for cyclogenesis due to strong monsoon currents.
    • This is also the period when the wind shear — that is, the difference between wind speeds at lower and upper atmospheric levels — is very high.
    • As a result, clouds do not grow vertically and monsoon depressions often fail to intensify into cyclones.
    • So it can be stated that this year, the cyclone season commenced earlier than usual. The last time a cyclone developed in the Bay of Bengal in September was Cyclone Day in 2018.

    Also read

    [Burning Issue] Tropical Cyclones and India

     

     

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  • Dinosaur Footprints found in Thar desert

    In a major discovery, footprints of three species of dinosaurs have been found in the Thar desert in Rajasthan’s Jaisalmer district.

    Details of the footprints

    • The footprints, made in the sediment or silt of the seashore, later become permanently stone-like.
    • They belong to three species of dinosaurs — Eubrontes cf. giganteus, Eubrontes glenrosensis and Grallator tenuis.
    • While the giganteus and glenrosensis species have 35 cm footprints, the footprint of the third species was found to be 5.5 cm.
    • The dinosaur species are considered to be of the theropod type, with the distinguishing features of hollow bones and feet with three digits.
    • All three species, belonging to the early Jurassic period, were carnivorous.
    • Eubrontes could have been 12 to 15 metres long and weighed between 500 kg and 700 kg, while the height of the Grallator is estimated to have been two metres, as much as a human, with a length of up to three metres.

    Key findings

    • The discovery of dinosaur footprints prove the presence of the giant reptiles in the western part of the State, which formed the seashore to the Tethys Ocean during the Mesozoic era.
    • Careful geological observations enabled the scientists to interpret ancient environments in which the rocks of the footprints, which were once soft sediments, were deposited.
    • Geochemical analyses and calculation of weathering indices showed that the hinterland climate was seasonal to semi-arid during the deposition of the footprints.
    • Fieldwork in the Kutch and Jaisalmer basins has suggested that after the main transgression during the early Jurassic period, the sea level changed several times.
    • Spatial and temporal distribution of sediments and traces of fossils and post-depositional structures provided an indication to this phenomenon.

    Significance

    • These trace fossils are significant to ascertain how life started and evolved after the mass extinction of species, including dinosaurs, at the end of the cretaceous period around 65 million years ago.
    • This research also illustrates the evidence of a fluvial freshwater palaeo-environment and tropical palaeo-climate, indicating the presence of a tropical forest and a huge network of rivers.

    No matter what, try this PYQ:

    Q.The term “sixth mass extinction/sixth extinction” is often mentioned in the news in the context of the discussion of (CSP 2018):

    (a) Widespread monoculture Practices agriculture and large-scale commercial farming with indiscriminate use of chemicals in many parts of the world that may result in the loss of good native ecosystems.

    (b) Fears of a possible collision of a meteorite with the Earth in the near future in the manner it happened 65million years ago that caused the mass extinction of many species including those of dinosaurs.

    (c) Large scale cultivation of genetically modified crops in many parts of the world and promoting their cultivation in other Parts of the world which may cause the disappearance of good native crop plants and the loss of food biodiversity.

    (d) Mankind’s over-exploitation/misuse of natural resources, fragmentation/loss, natural habitats, destruction of ecosystems, pollution, and global climate change.

     

    [wpdiscuz-feedback id=”vvcp20y3dc” question=”Please leave a feedback on this” opened=”1″]Post your answers here.[/wpdiscuz-feedback]

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  • Hurricane Ida makes landfall in US

    Hurricane Ida has made landfall in Louisiana, US as an extremely dangerous Category 4 storm.

    What is a Hurricane?

    • A hurricane is a tropical cyclone that occurs in the Atlantic Ocean and the northeastern Pacific Ocean.
    • And a typhoon occurs in the northwestern Pacific Ocean; in the south Pacific or the Indian Ocean, comparable storms are referred to simply as “tropical cyclones” or “severe cyclonic storms”.

    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.

    Try this question from CSP 2020:

    Q.Consider the following statements:

    1. Jet Streams occur in the Northern Hemisphere only.
    2. Only some cyclones develop an eye.
    3. The temperature inside the eye of a cyclone is nearly 10 degree Celsius lesser than that of the surroundings.

    Which of the statements given above is/are correct?

    (a) 1 only

    (b) 2 and 3 only

    (c) 2 only

    (d) 1 and 3 only

     

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    Destruction caused

    • Strong Winds: Cyclones are known to cause severe damage to infrastructure through high-speed winds.
    • Torrential rains and inland flooding: Torrential rainfall (more than 30 cm/hour) associated with cyclones is another major cause of damages. Unabated rain gives rise to unprecedented floods.
    • Storm Surge: A Storm surge can be defined as an abnormal rise of sea level near the coast caused by a severe tropical cyclone.

    Some (unexpected) benefits

    Although Tropical cyclones are known for the destruction they cause, when they strike they also bestow certain benefits to the climatic conditions of that area such as

    • Relieve drought conditions
    • Carry heat and energy away from the tropics and transport it towards temperate latitudes
    • Maintain a relatively stable and warm temperature worldwide

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    Also read:

    [Burning Issue] Tropical Cyclones and India

  • Hawaii’s Kilauea Volcano

    Geologists have detected a swarm of earthquakes at Hawaii’s Kilauea volcano, though it was not erupting.

    Kilauea Volcano

    • Kilauea is about 200 miles south of Honolulu, on the Big Island of Hawaii.
    • It is one of the world’s most active volcanoes, having erupted 34 times since 1952. In Hawaiian tradition, Kilauea is home to the volcano goddess Pele.
    • From 1983 to 2018, it erupted almost continuously, in some cases sending streams of lava that covered farms and homes.
    • At the end of this decades-long eruption, Kilauea spewed lava from vents in a residential neighborhood on its eastern flank and destroyed more than 700 homes.
    • In December, Kilauea erupted at the crater, creating a lake with enough lava to fill 10 Hoover dams. That eruption ended in May.

    Do not skip answering this PYQ:

    Consider the following statements:

    1. The Barren Island volcano is an active volcano located in the Indian Territory.
    2. Barren Island lies about 140 km east of Great Nicobar.
    3. The last time the Barren Island volcano erupted was in 1991 and it has remained inactive since then.

    Which of the statements given above is/are correct? (CSP 2014)

    (a) 1 only

    (b) 2 and 3 only

    (c) 3 only

    (d) 1 and 3 only

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    Back2Basics: Volcanic Landforms

    • Note the intrinsic and extrinsic types of volcanic landforms

    • A volcano has 3 main characteristics
    1. Cone shaped mountain
    2. Formed by rock or ash thrown from the inside of the earth
    3. At times, opening or depression at top
    • The three main types of volcanos are:

    1. Cinder cone Volcano: The cinder cones are small volcanoes with steep sides. Even though they are small, these are the ones you probably hear about.  They are very explosive and made of ash and rock.  Most of the cinder cones are small and less than 500 meters high.  A famous cinder cone is Sunset Crater Volcano in Arizona.
    2. Shield Volcanoes: A shield is a low and broad volcano that usually has a very wide crater (a dent in the Earth’s surface). It is formed from thin layers of lava after consistent low-grade eruptions.  The largest volcano in the world is a shield volcano.  It is located in Hawaii.
    3. Composite volcanoes: They are the tallest type of volcano. They look very impressive but do usually have quiet and slow lava flows.  They sometimes have small eruptions that cause ash and rock to go flying.  One of the most famous volcanoes in the world is a composite volcano.  It is Mount Fuji in Japan.