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Subject: Geographical Features

  • Venezuela Earthquake

    Why in News?

    A powerful doublet earthquake (Magnitude 7.2 followed by 7.5) struck Venezuela, killing over 188 people and injuring more than 1,500. It is the strongest earthquake to hit Venezuela in 126 years.

    Key Highlights

    • Two major earthquakes struck within one minute, making it a doublet earthquake.
    • Epicentres were located west of Caracas, near the coastal town of Morón.
    • Tremors were felt in Colombia and Brazil.
    • The earthquakes occurred at shallow depths (10 km and 22 km), resulting in severe ground shaking.
    • International humanitarian assistance was offered by India, the United States, the United Nations, China, Brazil, and others.

    Why Did the Earthquake Occur?

    • Plate Boundary: Venezuela lies along the boundary between the Caribbean Plate and the South American Plate.
    • Strike-slip Faulting: The Caribbean Plate moves eastward relative to the South American Plate, causing horizontal movement along faults.
    • Active Fault Zone: The earthquake occurred near the El Pilar Fault System, one of the most active fault systems in northern Venezuela.
    • Shallow-focus Earthquake: Shallow earthquakes release energy close to the Earth’s surface, leading to greater destruction.
    • Doublet Earthquake: Two large earthquakes occurring almost simultaneously amplify structural damage.

    Prelims Pointers

    • Earthquake: Sudden release of energy in the Earth’s crust due to movement along faults.
    • Focus (Hypocentre): Point inside the Earth where an earthquake originates.
    • Epicentre: Point on the Earth’s surface directly above the focus.
    • Shallow-focus earthquakes: Depth less than 70 km; generally cause maximum damage.
    • Strike-slip fault: Fault where two blocks move horizontally past each other.
    • Doublet earthquake: Two major earthquakes of similar magnitude occurring close together in time and location.

    [2023] Consider the following statements :
    1. In a seismograph, P waves are recorded earlier than S waves.
    2. In P waves, the individual particles vibrate to and fro in the direction of wave propagation whereas in S waves, the particles vibrate up and down at right angles to the direction of wave propagation.
    Which of the statements given above is/are correct?

    [A] 1 only

    [B] 2 only

    [C] Both 1 and 2

    [D] Neither 1 nor 2

  • Big Island (Hawaii)

    Why in the news?

    A magnitude 6.0 earthquake struck near Honaunau-Napoopoo on the Big Island.

    About the Big Island

    • The largest island in the Hawaiian archipelago
    • Part of Hawaii in the Pacific Ocean
    • Area: ~10,432 km²
    • Formed through volcanic activity

    Five Major Volcanoes

    • Kohala
    • Hualālai
    • Mauna Kea
    • Mauna Loa
    • Kīlauea

    Important Volcanoes

    Mauna Loa

    • One of the world’s largest volcanoes
    • Shield volcano
    • Greatest mass of any mountain on Earth

    Kīlauea

    • Among the world’s most active volcanoes
    • Frequently erupting since 1983

    Shield Volcano

    • A volcano with broad, gentle slopes formed by fluid lava flows. Examples: Mauna Loa and Kīlauea

    Mauna Kea

    • The highest point in Hawaii above sea level
    • Hosts major astronomical observatories

    Hawaiʻi Volcanoes National Park

    • UNESCO World Heritage Site
    • Protects Kīlauea and Mauna Loa volcanoes

    Why are Earthquakes Common in Hawaii?

    Due to:

    • Volcanic activity
    • Movement of tectonic plates
    • Hotspot volcanism

    Hotspot Volcanism

    • A hotspot is a place where hot magma rises from Earth’s mantle. As the Pacific Plate moves over it, volcanic islands form.

    [2024] Consider the following:
    1. Pyroclastic debris
    2. Ash and dust
    3. Nitrogen compounds
    4. Sulphur compounds
    How many of the above are products of volcanic eruptions?

    [A] Only one

    [B] Only two

    [C] Only three

    [D] All four

  • Mayon Volcano 

    Why in the News

    The Mayon Volcano recently erupted, leading to the evacuation of thousands of people in affected areas of the Philippines.

    About Mayon Volcano

    • Type: Active stratovolcano (composite volcano)
    • Location: Albay province, Luzon Island
    • Height: 2,462 metres
    • Known as: “World’s most perfect volcanic cone” due to its symmetry

    Geographical Setting

    • Part of the Pacific Ring of Fire
    • Located near the Philippine Trench
    • Formed at a convergent plate boundary
      • Philippine Sea Plate subducting beneath the Philippine Mobile Belt

    What is a Stratovolcano

    • Tall, steep cone shaped volcano
    • Built from alternating layers of:
      • Lava
      • Pyroclastic material
    • Found mainly in subduction zones
    • Magma type:
      • Andesite and dacite (viscous lava)
    • Leads to explosive eruptions
    [2024] Consider the following: 
    1. Pyroclastic debris 
    2. Ash and dust 
    3. Nitrogen compounds 
    4. Sulphur compounds 
    How many of the above are products of volcanic eruptions? 
    [A] Only one [B] Only two [C] Only three [D] All four

  • El Niño Likely to Develop After July 2026: WMO

    Why in the News

    The World Meteorological Organization has indicated high chances of the development of El Niño in the second half of 2026, after the current **La Niña conditions weaken and transition to ENSO-neutral.

    What is El Niño?

    • El Niño is the warm phase of the El Niño–Southern Oscillation (ENSO).
    • It is a periodic warming of sea surface temperatures in the central and eastern equatorial Pacific Ocean.
    • This warming disrupts global atmospheric circulation and affects weather patterns worldwide.

    ENSO Phases

    • El Niño (Warm Phase)
      • Warmer Pacific Ocean temperatures.
      • Often linked to weaker monsoon rainfall in India.
    • La Niña (Cool Phase)
      • Cooler-than-normal Pacific waters.
      • Often associated with stronger monsoon rainfall in India.
    • ENSO Neutral
      • Neither El Niño nor La Niña conditions.
    • Currently, La Niña is weakening, and neutral conditions are expected soon.

    Impact on India

    • India receives over 70% of annual rainfall during the southwest monsoon (June–September).
    • July and August alone contribute more than 50% of seasonal rainfall.
    • If El Niño develops after July, it could reduce monsoon rainfall and affect agriculture, water supply, and food production.

    Key Prelims Points

    • ENSO occurs in the equatorial Pacific Ocean.
    • El Niño years often correlate with weaker Indian monsoon, though not always.
    • Monitoring agencies include IMD and WMO.
    • ENSO affects temperature, rainfall, cyclones, and global climate patterns.
    [2011] La Nina is suspected to have caused recent floods in Australia. How is La Nina different from EI Nino? La Nina is characterized by unusually cold ocean temperature in the equatorial Indian ocean whereas EI Nino is characterized by unusually warm ocean temperature in the equatorial Pacific Ocean. EI Nino has an adverse effect on the southwest monsoon of India, but La Nina has no effect on monsoon climate. Select the correct answer using the code given below: (a) 1 only (b) 2 only (c) Both 1 and 2 (d) Neither 1 nor 2

  • Satellite data show India’s major deltas sinking

    Why in the News

    A global study published in Nature on 14 January reports widespread land subsidence across India’s major river deltas, driven largely by human activities and observed using Sentinel 1 satellite data.

    Study at a Glance

    • Data source Interferometric Synthetic Aperture Radar from ESA Sentinel 1
    • Period 2014 to 2023
    • Coverage 40 major global deltas including 6 Indian deltas
    • Spatial resolution 75 metres
    • Population relevance Deltas support over 340 million people globally

    Indian Deltas Confirmed to be Sinking

    • Ganges Brahmaputra Delta, Brahmani Delta, Mahanadi Delta, Godavari Delta, Cauvery Delta and Kabani Delta.
    • More than 90 percent area affected in Ganges Brahmaputra, Brahmani and Mahanadi deltas.

    Key Quantitative Findings

    • Brahmani delta: 77 percent area sinking at more than 5 mm per year
    • Mahanadi delta: 69 percent area sinking at more than 5 mm per year
    • In Ganges, Brahmani, Mahanadi, Godavari and Kabani,
       Subsidence rate exceeds regional sea level rise
    • Godavari delta: Even 95th percentile subsidence exceeds projected global sea level rise under worst climate scenario
    • Kolkata: Subsidence equals or exceeds delta average due to urban load and resource extraction

    Major Human Drivers Identified

    • Unsustainable groundwater extraction: Ganges Brahmaputra and Cauvery deltas
    • Rapid urbanisation: Brahmani delta
    • Reduced sediment flux: Mahanadi and Kabani deltas
    • Population pressure: Intensifies compaction and land lowering
    [2018] Which of the following is/are the possible consequence/s of heavy sand mining in riverbeds? 

    1. Decreased salinity in the river 

    2. Pollution of groundwater 

    3. Lowering of the water-table 

    Select the correct answer using the code given below: 

    (a) 1 only (b) 2 and 3 only (c) 1 and 3 only (d) 1, 2 and 3

  • Minamitori Island  

    Why in the News?

    Japan has decided to conduct test mining of rare earth rich mud from the deep seabed near Minamitori Island to reduce dependence on imported critical minerals.

    About Minamitori Island

    • Minamitori Island is also known as Marcus Island.
    • It is an isolated Japanese coral atoll located in the northwestern Pacific Ocean.
    • It marks the easternmost territorial point of Japan.
    • It is the first location in Japan to witness sunrise due to its eastern position.
    • The island is situated about 1,950 kilometres southeast of central Tokyo.

    Geographical and Geological Features

    • Minamitori Island represents the exposed summit of a massive underwater seamount.
    • The seamount rises from the deep ocean floor along the Marcus Necker Ridge.
    • It is the only landmass of Japan that lies entirely on the Pacific Plate.
    • The island provides Japan with a large Exclusive Economic Zone in the Pacific Ocean.

    What is Rare Earth Mud

    • Rare earth mud is a type of pelagic sediment formed from the accumulated remains of plankton.
    • Over millions of years, these sediments become enriched with rare earth elements.
    • The mud contains significant quantities of neodymium and dysprosium.
    • These elements are essential for manufacturing high performance permanent magnets.
    Consider the following statements: (2021)

    1. The Global Ocean Commission grants licenses for seabed exploration and mining in international waters. 

    2. India has received licenses for seabed mineral exploration in international waters. 

    3. ‘Rare earth minerals’ are present on the seafloor in international waters. 

    Which of the statements given above are correct? 

    (a) 1 and 2 only (b) 2 and 3 only (c) 1 and 3 only (d) 1, 2, and 3

  • Chillai Kalan Begins in Kashmir 

    Why in the News?

    The higher reaches of Kashmir Valley witnessed snowfall and the plains received rain as Chillai-Kalan, the harshest 40 day winter phase, began on December 21, 2025.

    What is Chillai Kalan

    • Meaning: Big cold in Kashmiri
    • Duration: 40 days
    • Period: December 21 to January 30
    • Significance: Coldest phase of winter in Kashmir
    • Belief: Rain or snow on the first day is considered a good omen and indicates heavy snowfall ahead

    Importance of the Precipitation

    • Ended a prolonged dry spell in the Valley
    • Helped reduce dust and dryness
    • Expected to improve water availability and snow reserves
    • Dry winter last year had caused
      • Health issues like cough and cold
      • Problems for agriculture and tourism sector

    Follow-Up Cold Phases

    After Chillai Kalan, Kashmir experiences two shorter cold spells

    • Chillai Khurd meaning small cold
    • Chillai Bacha meaning baby cold

    Prelims Pointers

    • Chillai Kalan is unique to Kashmir climate tradition
    • Heavy snowfall during this phase replenishes glaciers and water sources
    • Gulmarg and Sonamarg are key winter tourism centres
    • Sadhna Top is strategically important due to its proximity to the Line of Control
    [2015] 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 North-Western region of India are part of westerlies. 

    Which of the statements given above is/are correct? 

    (a) 1 only (b) 2 only (c) Both 1 and 2 (d) Neither 1 nor 2

  • Kavachi Volcano

    Why in the News?

    Scientists have reported rare underwater footage showing sharks living inside the crater of Kavachi volcano, near the Solomon Islands. This discovery challenges earlier assumptions about marine survival in extreme volcanic environments.

    About Kavachi Volcano

    • A shallow submarine volcano located in the South Pacific Ocean
    • Situated south of Vangunu Island in the Solomon Islands
    • Lies on the Pacific Ring of Fire, a highly tectonically active zone
    • Among the few active and visible undersea volcanoes in the world

    Volcanic Activity

    • Known for frequent but unpredictable eruptions
    • First documented eruptive activity in 1939
    • Has experienced multiple temporary island forming events

    Prelims Pointers

    • Type: Submarine volcano
    • Location: South Pacific Ocean
    • Tectonic setting: Pacific Ring of Fire
    • Key feature: Temporary island formation
    • Recent relevance: Sharks observed inside a volcanic crater

    [2024] Consider the following: 1. Pyroclastic debris 2. Ash and dust 3. Nitrogen compounds 4. Sulphur compounds. How many of the above are products of volcanic eruptions? 

    (a) Only one

    (b) Only two

    (c) Only three

    (d) All four 

  • Hormuz Island

    Why in the News?

    • A rare natural phenomenon turned the coastlines of Hormuz Island into a blood red landscape, drawing global attention

    About Hormuz Island

    • Location: Iran, on the Strait of Hormuz
     • Lies between the Persian Gulf and the Gulf of Oman
     • Situated about 8 km off the Iranian coast
     • Area: 41.9 sq km
     • A hilly island with distinctive geomorphology

    Geological Features

    • Composed mainly of sedimentary rocks and volcanic ash
     • Dominant red colour due to high iron oxide content
     • Presence of hematite mineral gives the soil its deep red hue
     • Ocean waves turn pink when they wash over iron rich sands

    Soil and Climate

    • Experiences low precipitation
     • Soil and water are saline in nature
     • Landscape is largely barren

    Unique Identity

    • Known as Rainbow Island due to multi coloured soil
     • Sand and soil colours include red, gold, silver, and white

    Human Settlement and Livelihood

    • Hormuz village is the only permanent settlement
     • Fishing is the primary source of livelihood
     • Inhabited mainly by the Bandari ethnic group

    What is the importance of developing Chabahar Port by India? (2017)

    (a) India’s trade with African countries will enormously increase. 

    (b) India’s relations with oil-producing Arab countries will be strengthened. 

    (c) India will not depend on Pakistan for access to Afghanistan and Central Asia. 

    (d) Pakistan will facilitate and protect the installation of a gas pipeline between Iraq and India.

  • Bitra Island

    Why in the News?

    The Chief of Staff, Southern Naval Command, announced that the Indian Navy is setting up a detachment on Bitra Island, and the facility is almost completed. This will make Bitra the third island in Lakshadweep to host a defence establishment.

    About Bitra Island

    • Location: Northern Lakshadweep, Arabian Sea
    • Smallest inhabited island in Lakshadweep
    • Land area: 0.105 sq. km
    • Dimensions: Length – 0.57 km | Width – 0.28 km
    • Lagoon area: 45.61 sq. km (significantly larger than the landmass)
    • Population (2011): 271

    Key Features

    • Cultural Significance: Hosts a shrine of Malik Mulla, an Arab saint believed to be buried there.
      • Important pilgrimage site for locals across Lakshadweep.
    • Ecology: Once covered with thick shrubs.
      • Historically a major breeding ground for seabirds, which declined in the 19th century due to human interference.
    • Climate: Similar to Kerala’s climate.
    • Hottest months: March–May
    • Temperature: 25°C – 35°C
    • Humidity: 70–76% throughout most of the year.

    Strategic Importance

    • Located in a key position in the Arabian Sea, critical for maritime security.
    • Enhances surveillance over sea lanes close to India’s western maritime frontier.
    • Adds to Lakshadweep’s defence infrastructure:
      • INS Dweeprakshak – Kavaratti
      • INS Jatayu – Minicoy
      • New Navy detachment – Bitra Island

    Prelims Pointers

    • Bitra = smallest inhabited island of Lakshadweep
    • Features a shrine of Malik Mulla
    • Large lagoon-to-land ratio
    • Strategically vital for India’s naval presence in the Arabian Sea
    • Climate closely resembles Kerala
    Which one of the following pairs of islands is separated from each other by the ‘Ten Degree Channel’? (2014)

    (a) Andaman and Nicobar 

    (b) Nicobar and Sumatra 

    (c) Maldives and Lakshadweep 

    (d) Sumatra and Java