GEOLOGY

Detailed explanation-1: -Pyroclastic material is likely to form from high-viscosity lava. Pyroclastic material is a cloud of lava fragments and ash, and viscosity means thickness (so high-viscosity lava will be thicker than low-viscosity lava).

Detailed explanation-2: -These form as a result of the the expansion of gas in as viscous magma rises to the surface. Since low viscosity magma have low gas content, it is not likely to form significant proportions of pyroclastic material.

Detailed explanation-3: -Pyroclastic flows contain a high-density mix of hot lava blocks, pumice, ash and volcanic gas. They move at very high speed down volcanic slopes, typically following valleys.

Detailed explanation-4: -Pyroclasts are derived from either the magma itself or are plucked as solid pieces from the walls of the conduit, usually near the surface. Pyroclasts and pyroclastic rocks may be seen in most parks that contain volcanoes or volcanic rocks.

Detailed explanation-5: -pyroclastic flow, in a volcanic eruption, a fluidized mixture of hot rock fragments, hot gases, and entrapped air that moves at high speed in thick, gray-to-black, turbulent clouds that hug the ground.