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Subject: Geography

  • What is a Supermoon?

    The Moon will have the nearest approach to Earth on May 26, and therefore will appear to be the closest and largest Full Moon or “supermoon” of 2021.

    Tap here to read more about Solar and Lunar Eclipses

    What is a Supermoon?

    • A supermoon occurs when the Moon’s orbit is closest to the Earth at the same time that the Moon is full.
    • As the Moon orbits the Earth, there is a point of time when the distance between the two is the least (called the perigee when the average distance is about 360,000 km from the Earth).
    • Also, there is a point of time when the distance is the most (called the apogee when the distance is about 405,000 km from the Earth).
    • Now, when a full moon appears at the point when the distance between the Earth and the Moon is the least, not only does it appear to be brighter but it is also larger than a regular full moon.
    • According to NASA, the term supermoon was coined by astrologer Richard Nolle in 1979.
    • In a typical year, there may be two to four full supermoons and two to four new supermoons in a row.

    What is happening today?

    • Two celestial events will take place at the same time.
    • One is the supermoon and the other is a total lunar eclipse, which is when the Moon and Sun are on opposite sides of the Earth.
    • Because of the total lunar eclipse, the moon will also appear to be red.
    • This is because the Earth will block some of the light from the Sun from reaching the moon.
    • The Earth’s atmosphere filters the light, it will soften “the edge of our planet’s shadow” “giving the Moon a deep, rosy glow.”

  • Eruption of Mount Nyiragongo

    Thousands have fled a volcanic eruption in the Democratic Republic of Congo from Mount Nyiragongo on the outskirts of Goma City.

    These were some volcanoes in news this year:

    Mount Vesuvius, Taal Volcano, La Soufriere

    Mount Nyiragongo

    • Mount Nyiragongo is an active stratovolcano with an elevation of 3,470 m (11,385 ft) in the Virunga Mountains associated with the Albertine Rift.
    • The main crater is about 2km wide and usually contains a lava lake.
    • The crater presently has two distinct cooled lava benches within the crater walls.
    • It is one of the 16 Decade Volcanoes.
    • Nyiragongo’s lava lake has at times been the most voluminous known lava lake in recent history. The depth of the lava lake varies considerably.
    • Nyiragongo and nearby Nyamuragira are together responsible for 40 percent of Africa’s historical volcanic eruptions.

    Answer this PYQ in the comment box:

    Q.Which of the following adds/add carbon dioxide to the carbon cycle on the planet Earth?

    1. Volcanic action
    2. Respiration
    3. Photosynthesis
    4. Decay of organic matter

    Select the correct answer using the code given below:

    (a) 1 and 3 only

    (b) 2 only

    (c) 1, 2 and 4 only

    (d) 1, 2, 3 and 4

    What are Decade Volcanoes?

    • The Decade Volcanoes are 16 volcanoes identified by the International Association of Volcanology and Chemistry of the Earth’s Interior (IAVCEI).
    • They are considered worthy of particular study in light of their history of large, destructive eruptions and proximity to densely populated areas.
    • They are named Decade Volcanoes because the project was initiated in the 1990s as part of the United Nations-sponsored International Decade for Natural Disaster Reduction.

  • Cyclone Tauktae

    Cyclone Tauktae (pronounced Tau-Te), classified as a very severe cyclonic storm (VSCS) and developed in the Arabian Sea, is wreaking havoc all across the Indian Coast.

    Don’t you think?

     In recent years, strong cyclones have been developing in the Arabian Sea more frequently than earlier.

    Cyclone Tauktae

    • Tauktae is a currently active and strengthening tropical cyclone threatening the state of Gujarat in India and impacting the states Karnataka, Goa and Maharashtra.
    • It is the fourth cyclone in consecutive years to have developed in the Arabian Sea, that too in the pre-monsoon period (April to June).
    • All these cyclones since 2018 have been categorised as either ‘Severe Cyclone’ or above.
    • Once Tauktae makes its landfall, three of these will have hit either the Gujarat or Maharashtra coast.
    • After Cyclone Mekanu in 2018, which struck Oman, Cyclone Vayu in 2019 struck Gujarat, followed by Cyclone Nisarga in 2020 that struck Maharashtra.

    What is aiding such rapid intensification?

    • Any tropical cyclone requires energy to stay alive.
    • This energy is typically obtained from the warm water and humid air over the tropical ocean.
    • Currently, seawater up to depths of 50 metres has been very warm, supplying ample energy to enable the intensification of Cyclone Tauktae.
    • The more the heat released through condensation of water vapour, the steeper the drop in pressure.
    • A low-pressure system undergoes multiple stages of intensification to form cyclones.

    Not a rare phenomenon

    • Typically, tropical cyclones in the North Indian Ocean region (the Bay of Bengal and the Arabian Sea) develop during the pre-monsoon and post-monsoon (October to December) periods.
    • May-June and October-November are known to produce cyclones of severe intensity that affect the Indian coasts.

    Is the Arabian Sea becoming cyclone-friendly?

    • Annually, five cyclones on average form in the Bay of Bengal and the Arabian Sea combined.
    • Of these, four developments in the Bay of Bengal, which is warmer than the Arabian Sea.
    • In the Arabian Sea, cyclones typically develop over the Lakshadweep area and largely traverse westwards, or away from India’s west coast.
    • However, in recent years, meteorologists have observed that the Arabian Sea, too, has been warming. This is a phenomenon associated with global warming.

    Back2Basics: Tropical Cyclone

    • 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 northwestern Pacific Ocean.
    • In the south Pacific or the Indian Ocean, comparable storms are referred to simply as “tropical cyclones” or “severe cyclonic storms”.

    Also read:

    [Burning Issue] Tropical Cyclones and India

  • Major seismic hazard along Assam faultline

    Location of epicentre

    • An earthquake of magnitude 6.4 on the Richter scale hit Assam around 8 am on Wednesday.
    • The primary earthquake had its epicentre at latitude 26.690 N and longitude 92.360 E, about 80 km northeast of Guwahati, and a focal depth of 17 km, the National Centre for Seismology (NCS) said.

    The faultline

    • The preliminary analysis shows that the events are located near to Kopili Fault closer to Himalayan Frontal Thrust (HFT).
    • The Kopili Fault is a 300-km northwest-southeast trending fault from the Bhutan Himalaya to the Burmese arc.
    • The fault is a fracture along which the blocks of crust on either side have moved relative to one another parallel to the fracture.
    • The area is seismically very active falling in the highest Seismic Hazard zone V associated with collisional tectonics where Indian plate sub-ducts beneath the Eurasian Plate the NCS report said.
    • HFT, also known as the Main Frontal Thrust (MFT), is a geological fault along the boundary of the Indian and Eurasian tectonic plates.

    Need for earthquake preparedness

    • The Northeast is located in the highest seismological zone, so we must have constant earthquake preparedness at all levels.
    • Continuous tectonic stress keeps building up particularly along the faultlines.
    • Today’s earthquake was an instance of accumulated stress release — probably, stress was constrained for a fairly long time at this epicentre, and hence the release was of relatively higher intensity.

  • [pib] Satellite-based real-time monitoring of Himalayan glacial catchments

    Melting of glaciers in Himalaya and GLOFs

    • The Himalayan region is home to the largest ice mass outside of the planet’s Polar Regions.
    • The glaciers in the Himalayas are melting at a faster rate creating new lakes and expanding the existing ones.
    • The rising temperatures and extreme precipitation events make the region increasingly prone to a variety of natural hazards, including devastating glacial lake outburst floods (GLOFs).
    • GLOFs occur when either a natural dam containing a glacial lake bursts or when the lake’s level suddenly increases and overflows its banks, leading to catastrophic downstream destruction.
    • However, the remote, challenging Himalayan terrain and the overall lack of cellular connectivity throughout the region have made the development of early flood warning systems virtually impossible.
    • In their recent work the Scientists point out that the surge of meltwater in mountain streams is most commonly caused by cloud-burst events during the monsoon season (June–July–August) time frame.

    Satelitte-based real-time monitoring

    • Satellite-based real-time monitoring of Himalayan glacial catchments would improve understanding of flood risk in the region and help inform an early flood warning system that could help curb disaster and save human lives, says a recent study.
    • This should be the future strategy to reduce loss of human lives during glacial lake outburst floods (GLOF), said a study carried out by scientists from IIT Kanpur.
    • The IIT Kanpur team suggests that efforts to help mitigate GLOF events in the future should include the creation of a network of satellite-based monitoring stations that could provide in situ and real-time data on GLOF risk.
    • The integration of monitoring devices with satellite networks will not only provide telemetry support in remote locations that lack complete cellular connectivity but will also provide greater connectivity in coverage in the cellular dead zones in extreme topographies such as valleys, cliffs, and steep slopes.

  • La Soufriere volcanic eruption

    Sulphur dioxide (SO2) emissions from La Soufriere volcano eruption in the Caribbean have reached all the way to India.

    Why in news?

    • Its eruption has sparked fear of increased pollution levels in the northern parts of India and acid rain.
    • Volcanic plumes can cause aviation and air quality hazards.

    La Soufriere

    • It is an active stratovolcano on the Caribbean island of Saint Vincent in Saint Vincent and the Grenadines.
    • It is the highest peak in Saint Vincent and has had five recorded explosive eruptions since 1718.

    Impact of such eruptions

    • Volcanic emissions reaching the stratosphere can have a cooling effect on global temperatures.
    • The most significant climate impacts from volcanic injections into the stratosphere come from the conversion of sulphur dioxide to sulphuric acid, which condenses rapidly in the stratosphere to form fine sulphate aerosols.
    • The aerosols increase the reflection of radiation from the Sun back into space, cooling the Earth’s lower atmosphere or troposphere.

    Try this PYQ:

    Q.Which of the following adds/add carbon dioxide to the carbon cycle on the planet Earth?

    1. Volcanic action
    2. Respiration
    3. Photosynthesis
    4. Decay of organic matter

    Select the correct answer using the code given below:

    (a) 1 and 3 only

    (b) 2 only

    (c) 1, 2 and 4 only

    (d) 1, 2, 3 and 4

  • How Asian desert dust enhances Indian summer monsoon?

    A new study has revealed how dust coming from the deserts in West, Central and East Asia plays an important role in the Indian Summer Monsoon.

    Try this PYQ:

    With reference to ‘Indian Ocean Dipole (IOD)’, sometimes mentioned in the news while forecasting Indian monsoon, which of the following statements is/are correct?

    1. IOD phenomenon is characterized by a difference in sea surface temperature between tropical Western Indian Ocean and tropical Eastern Pacific Ocean.
    2. An IOD phenomenon can influence an El Nino’s impact on the monsoon.

    Select the correct Option using the code given below:

    (a) Only 1

    (b) Only 2

    (c) Both 1 and 2

    (d) Neither 1 nor 2

    Why study dust?

    • Many studies have shown that the dust emission scheme is extremely sensitive to climate change.
    • Understanding these mechanisms and effects of dust will help us understand our monsoon systems in the face of global climate change.

    Impact of dust on Indian Monsoon

    • Dust swarms from the desert when lifted by strong winds can absorb solar radiation and become hot.
    • This can cause heating of the atmosphere, change the air pressure, wind circulation patterns, influence moisture transport and increase precipitation and rainfall.
    • A strong monsoon can also transport air to West Asia and again pick up a lot of dust.
    • The researchers say this is a positive feedback loop.

    Role of the Iranian plateau

    • Not just the dust from the Middle East, the Iranian Plateau also influences the Indian Summer Monsoon.
    • The hot air over the Iranian Plateau can heat the atmosphere over the plateau, strengthen the circulation over the deserts of the Arabian Peninsula and increase dust emission from the Middle East.
    • The researchers also explain how the Indian Summer Monsoon has a reverse effect and can increase the winds in West Asia to produce yet more dust.

    Transported aerosols

    • Deserts across the globe play important roles in monsoons.
    • The dust aerosols from deserts in West China such as the Taklamakan desert and the Gobi Desert can be transported eastward to eastern China and can influence the East Asia summer monsoon.
    • And in the southwest United States, we have some small deserts that influence the North African monsoon.

    Anthropogenic contributions

    • Some studies have found that the anthropogenic aerosols emitted from the Indian subcontinent can decrease summer monsoon precipitation.
    • However, some others found that absorbing aerosols such as dust can strengthen the monsoon circulation.

    Minor components

    • Earlier it was believed that dust from deserts across the globe will have the same components.
    • But it was found that different deserts have different chemical compositions and this can influence the dust’s properties.
    • For example, dust from the Middle East has the more absorbing ability of solar radiation than dust from North Africa and this difference in absorbing ability might influence monsoon systems.

  • Indian monsoon 25 million years ago resembled present day Australia’s

    Using leaf fossils, researchers have found that the Indian monsoon 25 million years ago resembled present-day Australia’s.

    Try this PYQ:

    Q.Which one of the following is the appropriate reason for considering the Gondwana rocks as the most important rock systems of India?

    (a) More than 90% of limestone reserves of India are found in them

    (b) More than 90% of India’s coal reserves are found in them

    (c) More than 90% of fertile black cotton soils are spread over them

    (d) None of the reasons given above is appropriate in this context

    India’s drift

    • About 180 million years ago, India separated from the ancient supercontinent Gondwana and took a long northward journey of about 9,000 km to join Eurasia.
    • During this journey, the subcontinent moved from the southern hemisphere, crossed the Equator to reach its current position in the northern hemisphere.
    • Due to these changing latitudes, it experienced different climatic conditions, and a new study has now tried to map these climatic variations using leaf fossils.

    Clueless over the evolution of monsoon

    • The evolution of the monsoonal climate in India is still debatable and not fully understood.
    • Though recent data indicates that the monsoon system we experience now dates back to about 25 million years, it is still unclear how the climate was during its long voyage.

    Indian research

    • The researchers analysed the morphological characters of fossil leaves collected from Deccan Volcanic Province, East Garo Hills of Meghalaya, Gurha mine in Rajasthan and Makum Coalfield in Assam.
    • The four fossil assemblages were found to be from four different geological ages.
    • It has been observed from across the globe that plant leaf morphological characters such as apex, base and shape are ecologically tuned with the prevailing climatic conditions.
    • The research applied this model to characterize the past monsoon from fossil leaves.

    It’s finding

    • The results indicated that the fossil leaves from India were adapted to an Australian type of monsoon and not the current Indian monsoon system during its voyage.
    • The reconstructed temperature data show that the climate was warm (tropical to subtropical) at all the studied fossil sites with temperatures varying from 16.3–21.3 degrees C.
    • All the fossil sites experienced high rainfall, which varied from 191.6 cm to 232 cm.

  • [pib] Coalition for Disaster resilient Infrastructure (CDRI)

    The Prime Minister has recently addressed the third edition of the annual conference of the Coalition for Disaster resilient Infrastructure (CDRI).

    What is CDRI?

    • The CDRI is an international coalition of countries, UN agencies, multilateral development banks, the private sector, and academic institutions that aim to promote disaster-resilient infrastructure.
    • Its objective is to promote research and knowledge sharing in the fields of infrastructure risk management, standards, financing, and recovery mechanisms.
    • It was launched by the Indian PM Narendra Modi at the 2019 UN Climate Action Summit in September 2019.
    • CDRI’s initial focus is on developing disaster-resilience in ecological, social, and economic infrastructure.
    • It aims to achieve substantial changes in member countries’ policy frameworks and future infrastructure investments, along with a major decrease in the economic losses suffered due to disasters.

    Try this PYQ:

    Q.Consider the following statements:

    1. Climate and Clean Air Coalition (CCAC) to Reduce Short Lived Climate Pollutants is a unique initiative of G20 group of countries
    2. The CCAC focuses on methane, black carbon and hydrofluorocarbons.

    Which of the above statements is/are correct?

    (a) 1 only

    (b) 2 only

    (c) Both 1 and 2

    (d) Neither 1 nor 2

    Its inception

    • PM Modi’s experience in dealing with the aftermath of the 2001 Gujarat earthquake” as the chief minister led him to the idea.
    • The CDRI was later conceptualized in the first and second edition of the International Workshop on Disaster Resilient Infrastructure (IWDRI) in 2018-19.
    • It was organized by the National Disaster Management Authority (NDMA), in partnership with the UN Office for Disaster Risk Reduction (UNDRR), the UN Development Programme, the World Bank, and the Global Commission on Adaptation.

    Its diplomatic significance

    • The CDRI is the second major coalition launched by India outside of the UN, the first being the International Solar Alliance.
    • Both of them are seen as India’s attempts to obtain a global leadership role in climate change matters and were termed as part of India’s stronger branding.
    • India can use the CDRI to provide a safer alternative to China’s Belt and Road Initiative (BRI) as well.

  • What is Rule Curve of a river?

    The Supreme Court has warned the Tamil Nadu Chief Secretary against the failure to give information on the rule curve for Mullaperiyar dam.

    Do you know?

    The Mullaperiyar dam is located in Kerala on the river Periyar but is operated and maintained by the neighbouring state of Tamil Nadu.

    What is the Rule Curve?

    • A rule curve or rule level specifies the storage or empty space to be maintained in a reservoir during different times of the year.
    • Here the implicit assumption is that a reservoir can best satisfy its purposes if the storage levels specified by the rule curve are maintained in the reservoir at different times.
    • It decides the fluctuating storage levels in a reservoir.
    • The gate opening schedule of a dam is based on the rule curve.
    • It is part of the “core safety” mechanism in a dam.

    Why such a move?

    • During the high-voltage hearing, the Tamil Nadu government blamed Kerala for delaying the finalization of the rule curve for the 123-year-old dam.
    • Kerala government has accused Tamil Nadu of adopting an “obsolete” gate operation schedule dating back to 1939.

    About Mullaperiyar Dam

    • Mullaperiyar Dam is a masonry gravity dam on the Periyar River in the Indian state of Kerala.
    • It is located on the Cardamom Hills of the Western Ghats in Thekkady, Idukki District of Kerala.
    • It was constructed between 1887 and 1895 by John Pennycuick and also reached an agreement to divert water eastwards to the Madras Presidency area (present-day Tamil Nadu).
    • It has a height of 53.6 m from the foundation, and a length of 365.7 m.
    • The Periyar National Park in Thekkady is located around the dam’s reservoir.
    • The dam is built at the confluence of Mullayar and Periyar rivers.