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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.

  • 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.

     

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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.

  • Water shortage in Colorado River Basin

    The federal government in the US has declared a water shortage for the Colorado river basin due to a historic drought.

    Try this PYQ

    Q. Consider the following pairs

    River – Flows into

    1. Mekong — Andaman Sea
    2. Thames — Irish Sea
    3. Volga — Caspian Sea
    4. Zambezi — Indian Ocean

    Which of the pairs given above is/are correctly matched?(CSP 2020)

    (a) 1 and 2 only

    (b) 3 only

    (c) 3 and 4 only

    (d) 1, 2 and 4 only

     

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    Colorado River

    • The Colorado River flows from the Rocky Mountains into the southwestern US and into Mexico.
    • The river is fed by snowmelt from the Rocky and Wasatch mountains and flows a distance of over 2,250 km (river Ganga flows through a distance of roughly 2,500 km) across seven states and into Mexico.
    • The Colorado River Basin is divided into the Upper (Wyoming, Colorado, New Mexico, Utah and northern Arizona) and Lower Basins (parts of Nevada, Arizona, California, southwestern Utah and western New Mexico).
    • In the Lower Basin, the Hoover Dam controls floods and regulates water delivery and storage.
    • Apart from the Hoover dam, there is the Davis Dam, Parker Dam and the Imperial Dam that regulate the release of water from the Hoover Dam.

    Major lakes in its basin

    • Lake Mead is the largest reservoir in the US in terms of volume and was formed in the 1930s by the Hoover Dam in Southern Nevada.
    • Its main source of water is obtained from the Rocky Mountain snowmelt and runoff.
    • The other is Lake Powell, the reservoir created by the Glen Canyon Dam in Arizona.

    Reasons for shortage

    • Since the year 2000, this river basin has been experiencing a prolonged drought.
    • This persistent drought has led to a lowering down of the water levels in the basin’s reservoirs to meet the demand over the years.
    • But even with great water storing capacity, over the years the demand for water from the basin has increased whereas supply is restricted.

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  • How the Moon ‘Wobble’ affects rising tides

    US coastlines will face increasing flooding in the mid-2030s due to a regular lunar cycle called the wobble effect that will magnify rising sea levels caused by climate change.

    What is the Moon Wobble?

    • The moon wobble is nothing but a regular swaying in the moon’s orbit.
    • It was first documented way back in 1728.
    • This wobble takes over an 18.6-year period to complete and continues in a cyclic fashion.

    How does this wobble occur?

    • High tides on this planet are caused mostly by the pull of the moon’s gravity on a spinning Earth. On most beaches, you would see two high tides every 24 hours.
    • The moon also revolves around the Earth about once a month, and that orbit is a little bit tilted.
    • moon’s orbital plane around the Earth is at an approximate 5-degree incline to the Earth’s orbital plane around the sun.
    • Because of that, the path of the moon’s orbit seems to fluctuate over time, completing a full cycle — sometimes referred to as a nodal cycle — every 18.6 years.
    • At certain points along the cycle, the moon’s gravitational pull comes from such an angle that it yanks one of the day’s two high tides a little bit higher, at the expense of the other.
    • This does not mean that the moon itself is wobbling, nor that its gravity is necessarily pulling at our oceans any more or less than usual.

    What impact does this wobble have on Earth?

    • Influences the ebb and flow of tides: The moon wobbles impacts the gravitational pull of the moon, and therefore, indirectly influences the ebb and flow of tides here on the Earth.
    • One half of the 18.6-year cycle suppresses the tides, which means that the high tides get lower, while the low tides get higher than normal.
    • Once this cycle completes, the situation flips—in the subsequent cycle, the tides are amplified, with high tides getting higher and low tides, lower.
    • The lunar cycle is expected to shift again by mid-2030, and in the coming phase, the tides will amplify once again.

    Moon wobble and climate change

    • The upcoming changes in the lunar cycle will pose a serious threat, as the amplified high tides coupled with the rising sea levels will make the risk of flooding far greater across all coastal regions of the globe.
    • The study predicts that the high tide-associated floods—also known as nuisance floods or sunny day floods—may occur in clusters that could last for months or even for longer periods!
    • This surge will be closely associated with the position of the Moon, Earth and the Sun.
    • When the Moon and Earth line up in specific ways with each other and the Sun, the resulting gravitational pull and the ocean’s corresponding response may leave city-dwellers coping with floods every day or two.

  • What is Summer Solstice?

    The summer solstice will happen today around 9:02 am on Monday (Indian Standard Time).

    What is Summer Solstice?

    • Solstice means “sun stands still” in Latin.
    • The longest day of 2021 for those living north of the Equator is June 21.
    • This day is characterized by a greater amount of energy received from the sun.
    • In technical terms, this day is referred to as the summer solstice, the longest day of the summer season. It occurs when the sun is directly over the Tropic of Cancer, or more specifically right over 23.5-degree north latitude.

    The Southern Hemisphere receives most sunlight on December 21, 22 or 23 when the northern hemisphere has its longest nights– or the winter solstice.

    Why do we have summer solstice?

    • Since Earth rotates on its axis, the Northern Hemisphere gets more direct sunlight between March and September over the course of a day.
    • This also means people living in the Northern Hemisphere experience summer during this time.
    • The rest of the year, the Southern Hemisphere gets more sunlight.
    • During the solstice, the Earth’s axis — around which the planet spins, completing one turn each day — is tilted in a way that the North Pole is tipped towards the sun and the South Pole is away from it.

    Answer this PYQ in the comment box:

    Q.On 21st June, the Sun (CSP 2019):

    (a) Does not set below the horizon at the Arctic Circle

    (b) Does not set below the horizon at Antarctic Circle

    (c) Shines vertically overhead at noon on the Equator

    (d) Shines vertically overhead at the Tropic of Capricorn

    Some other facts

    • Summer solstice does not mean the earliest sunrise or latest sunset.
    • Although June 21 will be the longest day in 2021, it does not necessarily mean that it brings the earliest sunrise or latest sunset.
    • It depends on the latitudinal location of the country.

  • [pib] Northern Limit of Monsoon (NLM)

    The Northern Limit of Monsoon (NLM) continues to pass through Diu, Surat, Nandurbar, Bhopal, Nowgong, Hamirpur, Barabanki, Bareilly, Saharanpur, Ambala & Amritsar.

    Try this question from CS Mains 2017:

    Q.What characteristics can be assigned to monsoon climate that succeeds in feeding more than 50 percent of the won population residing in Monsoon Asia?

    What is the Northern Limit of Monsoon?

    • NLM, is the northernmost boundary of India up to which monsoon rains have advanced on any given day.
    • So, it is a way of tracking the progress of monsoon clouds as they move over India’s landmass.
    • The India Meteorological Department (IMD) adds that the monsoon “advances northwards, usually in surges, and covers the entire country around July 15″.

    What are the Eastern and Western Arms?

    • It is the mountains of southern India that split the south-western winds, giving the Indian monsoon its ‘two arms.
    • The western arm of the monsoon is deflected northwards, by the Western Ghats, to (Mumbai) and then on to Pakistan.
    • The eastern arm travels up through the Bay of Bengal to (Kolkata) and Assam and is deflected north-westwards by the Himalayas.

    Also refer this link:

    Explain the formation of Indian monsoons. Highlight the link between monsoons and India’s cropping pattern. (15 marks)

  • Anti-hail guns to mitigate hailstorms crop damage

    To help out horticulturists who face crop damage due to hailstorms, the Himachal Pradesh government will be testing the use of indigenously developed ‘anti-hail guns’.

    What are anti-hail guns?

    • An anti-hail gun is a machine that generates shock waves to disrupt the growth of hailstones in clouds, according to its makers.
    • It comprises a tall, fixed structure somewhat resembling an inverted tower, several metres high, with a long and narrow cone opening towards the sky.
    • The gun is “fired” by feeding an explosive mixture of acetylene gas and air into its lower chamber, which releases a shock wave (waves that travel faster than the speed of sound, such as those produced by supersonic aircraft).
    • These shock waves supposedly stop water droplets in clouds from turning into hailstones, so that they fall simply as raindrops.

    Answer this PYQ in the comment box:

    Q.During a thunderstorm, the thunder in the skies is produced by the

    1. meeting of cumulonimbus clouds in the sky
    2. lightning that separates the nimbus clouds
    3. violent upward movement of air and water particles

    Select the correct option using the codes given below:

    (a) 1 only

    (b) 2 and 3 only

    (c) 1 and 3 only

    (d) None of the above

    How do they ‘prevent’ a hailstorm?

    • It is this hail formation process that the shock waves from anti-hail guns try to disrupt in a radius of 500 meters, so that the water droplets fall down before they can be lifted by the updrafts.
    • The machine is repeatedly fired every few seconds during an approaching thunderstorm.
    • However, the effectiveness of anti-hail guns has remained a contentious issue.

    How do Hailstorms occur?

    • Hail is produced by cumulonimbus clouds, which are generally large and dark and may cause thunder and lightning.
    • In such clouds, winds can blow up the water droplets to heights where they freeze into ice.
    • The frozen droplets begin to fall but are soon pushed back up by the winds and more droplets freeze onto them, resulting in multiple layers of ice on the hailstones.
    • This fall and rise is repeated several times, till the hailstones become too heavy and fall down.

  • Monsoon onset over Kerala delayed: IMD

    • The monsoon’s arrival over Kerala has been delayed to June 3, according to an update by the India Meteorological Department (IMD).
    • Private weather forecast agency, Skymet, however, said that the monsoon had arrived.
    • This was because two of the three criteria — as defined by the IMD — had been met.
    • Currently, IMD’s own data indicated that except for the OLR, the other criteria were met. Thus, there is an element of subjectivity in arrival.

    What are those criterias defined by IMD?

    1. Rain-bearing westerlies being at a minimum depth and speed;
    2. At least 60% of the available 14 stations in Kerala and coastal Karnataka, reporting rainfall of 2.5 mm or more for two consecutive days after May 10;
    3. A certain degree of clouding, indicated by a parameter called ‘outgoing long wave radiation’ (OLR), being below 200 W/square meter.

    What is meant by ‘Outgoing Long Wave Radiation’ (OLR)?

    • Outgoing Long-wave Radiation (OLR) is electromagnetic radiation of wavelengths from 3–100 μm emitted from Earth and its atmosphere out to space in the form of thermal radiation.
    • It is also referred to as up-welling long-wave radiation and terrestrial long-wave flux, among others.
    • The flux of energy transported by outgoing long-wave radiation is measured in W/m.
    • In the Earth’s climate system, long-wave radiation involves processes of absorption, scattering, and emissions from atmospheric gases, aerosols, clouds and the surface.
    • Over 99% of outgoing long-wave radiation has wavelengths between 4 μm and 100 μm, in the thermal infrared part of the electromagnetic spectrum.

    Factors responsible for south-west monsoon formation:

    1. Intense heating of Tibetan plateau during summer months.
    2. Permanent high pressure cell in the South Indian Ocean (east to north-east of Madagascar in summer).

    Factors that influence the onset of south-west monsoons:

    1. Above points +
    2. Subtropical Jet Stream (STJ).
    3. Tropical Easterly Jet (African Easterly Jet).
    4. Inter Tropical Convergence Zone.

    Factors that influence the intensity of south-west monsoons:

    1. Strengths of Low pressure over Tibet and high pressure over southern Indian Ocean.
    2. Somali Jet (Findlater Jet).
    3. Somali Current (Findlater Current).
    4. Indian Ocean branch of Walker Cell.
    5. Indian Ocean Dipole.

    Factors responsible for north-east monsoon formation:

    1. Formation and strengthening of high pressure cells over Tibetan plateau and Siberian Plateau in winter.
    2. Westward migration and subsequent weakening of high pressure cell in the Southern Indian Ocean.
    3. Migration of ITCZ to the south of India.