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Q57 (CDS-I/2022) Geography › World Physical Geography › Seismology and volcanism Answer Verified

Individual lava flows are normally only a few feet thick, but over a long period of time, repeated flows may build up a volcano. Such volcanoes are termed as :

Result
Your answer: —  Â·  Correct: A
Explanation

Shield volcanoes are primarily constructed from highly fluid basaltic lava flows [6]. Because the lava is very runny, it spreads far from the vent, creating broad, gentle slopes rather than steep cones [5]. These volcanoes are built up over long periods by the accumulation of thousands of individual lava flows that are typically only a few feet thick [6]. In contrast, composite volcanoes (or stratovolcanoes) are built from alternating layers of viscous lava, ash, and pyroclastic debris, resulting in much steeper profiles [2]. While composite volcanoes grow in height through successive eruptions, the specific characteristic of being built almost entirely by repeated, thin, fluid lava flows that create a broad, shield-like profile is the defining feature of a shield volcano [6]. Examples include the Hawaiian volcanoes Mauna Loa and Mauna Kea [5].

Sources

  1. [3] https://www.bgs.ac.uk/discovering-geology/earth-hazards/volcanoes/how-volcanoes-form/
  2. [6] Certificate Physical and Human Geography , GC Leong (Oxford University press 3rd ed.) > Chapter 3: Volcanism and Earthquakes > Extrusive Landforms > p. 30
  3. [1] Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 11: Volcanism > Shield Type Volcano > p. 141
  4. [5] Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 11: Volcanism > Composite Type Volcano (Stratovolcano) > p. 140
  5. [4] https://www.nps.gov/articles/000/shield-volcanoes.htm
  6. [2] https://pubs.usgs.gov/gip/volc/types.html
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