GEOLOGY

Detailed explanation-1: -Pyroclastic flow – expulsion of ash, cinders, bombs, and gases during an explosive volcanic eruption.

Detailed explanation-2: -Stratovolcano: A large, steep-sided, symmetrical cone built of alternating layers (strata) of lava, ash, cinders, blocks, and bombs. Also called composite volcano, these stratovolcanoes form some of Earth’s grandest mountains rising as much as 8, 000 feet above their bases (movie).

Detailed explanation-3: -In stratovolcanoes the collapse and formation of a caldera results from rapid evacuation of the underlying magma chamber by voluminous explosive eruptions that form extensive fall deposits and pyroclastic flows.

Detailed explanation-4: -Pyroclastic flows have their origin in explosive volcanic eruptions, when a violent expansion of gas shreds escaping magma into small particles, creating what are known as pyroclastic fragments.