Q. Which of the following statements with regard to volcanic structures is/are correct?
1.Shield volcanoes feature steep, precipitous slopes and are built by high-viscosity, silica-rich lava flows.
2.Stratovolcanoes are composite structures composed of alternating layers of hardened lava flows, volcanic ash, and tephra.
3.Cinder Cone volcanoes are typically small, steep-sided cones constructed from loose pyroclastic debris ejected during explosive eruptions.
Select the correct answer using the code given below:
Answer: B
Notes:
Explanation:
- Statement 1 is incorrect: Shield volcanoes have broad, gently sloping sides (resembling a warrior’s shield) and are formed by the eruption of low-viscosity, low-silica basaltic lava that flows easily over long distances, not high-viscosity lava.
- Statement 2 is correct: Stratovolcanoes (composite volcanoes) develop their characteristic steep profiles because they are built from sequential layers of thick, sticky lava flows alternating with explosive deposits of ash, cinders, and volcanic rocks.
- Statement 3 is correct: Cinder cones are the simplest type of volcano. They build up when gas-charged lava is blown violently into the air, breaks into small fragments (cinders), and falls back around the vent to form a circular or oval cone with a central bowl-shaped crater.
