Daily Static Quiz Prelims Practice 2027
Option (b) is correct — composite volcanoes (stratovolcanoes) like Mt. Fuji, Mt. Vesuvius, and Mt. St. Helens are built of alternating layers of solidified lava, ash, and pyroclastic deposits, with steep profiles and viscous, silica-rich lava that make eruptions explosive and dangerous. Option (a) is wrong — that description fits a composite volcano, not a shield volcano; shield volcanoes like Mauna Loa have gentle broad slopes and free-flowing basaltic lava producing quiet eruptions. Option (c) is wrong — a caldera is a depression formed by summit collapse after a massive eruption, not a dome-shaped elevation (that describes a lava dome). Option (d) is wrong — cinder cones are actually the smallest volcano type; the largest are shield volcanoes, typically found at hotspots or mantle plumes rather than exclusively mid-ocean ridges.
- The "Ring of Fire" encircling the Pacific Ocean accounts for approximately 75% of the world's active volcanoes and is associated with subduction zones where oceanic plates dive under continental or other oceanic plates.
- Mid-ocean ridges are sites of divergent plate boundaries where volcanic activity produces new oceanic crust, contributing to seafloor spreading.
- Intraplate volcanoes, such as those in Hawaii, are explained by the movement of tectonic plates over stationary hotspots or mantle plumes.
- The Himalayan mountain range is a region of intense volcanic activity due to the collision of the Indian and Eurasian plates.
Statements 1, 2 and 3 are correct. The Pacific Ring of Fire is the world's most volcanically and seismically active zone, linked to subduction of the Pacific Plate. Mid-ocean ridges are divergent boundaries where magma wells up to form new basaltic crust, driving seafloor spreading. Hawaii is a classic case of intraplate volcanism, as the Pacific Plate moves over a stationary mantle plume, creating a chain of progressively older islands. Statement 4 is incorrect — the Himalayas are a continental collision zone between the Indian and Eurasian plates, which produces mountain-building and earthquakes but not volcanism.
Reason (R): Subduction zone earthquakes typically occur at greater depths and involve larger fault surfaces, often triggering tsunamis when the ocean floor is suddenly displaced upward.
Both A and R are correct, and R explains A. Subduction zone earthquakes, such as the 2004 Indian Ocean and 2011 Tōhoku events, are among the most powerful ever recorded, including megathrust quakes above magnitude 9.0. This destructiveness stems from the enormous rupture area along the plate interface and the vertical displacement of the ocean floor, which generates tsunamis capable of devastating coasts thousands of kilometres away — as the 2004 Indian Ocean tsunami, which killed over 230,000 people, directly illustrates.
Option (b) is correctly matched — Krakatoa is an active volcanic island in the Sunda Strait, Indonesia, famous for its catastrophic 1883 eruption, heard nearly 5,000 km away and causing global temperature drops. Option (a) is wrong — Mt. Etna is in Sicily, Italy, not Greece, and is Europe's tallest active volcano. Option (c) is wrong — Popocatépetl is an active stratovolcano in Mexico, near Mexico City, not Argentina. Option (d) is wrong — Mt. Erebus is on Ross Island, Antarctica, not Norway, notable for one of the world's few persistent lava lakes.
Option (b) is correct — a tsunami results from the sudden vertical displacement of a large volume of water, most commonly by an undersea megathrust earthquake, but also by submarine volcanic eruptions or landslides. In open ocean, tsunamis have very long wavelengths and low heights, travelling up to 800 km/h, but slow and grow dramatically taller as they approach shallow coastal waters (shoaling). Option (a) describes a storm surge, an entirely different coastal-flooding mechanism caused by cyclones. Option (c) is wrong — tsunamis have long, not short, wavelengths and occur in open oceans, not enclosed bodies. Option (d) is wrong — the overwhelming majority of tsunamis are caused by natural geological events, not nuclear explosions.
