GEOLOGY

Detailed explanation-1: -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.

Detailed explanation-2: -Explosive eruptions can occur when viscous magma, such as rhyolite or andesite, erupts at the surface. The eruptions are powered by expanding volcanic gases, and by expanding steam if magma interacts with water. Explosive eruptions yield pyroclastic material consisting of ash and coarser debris thrown into the air.

Detailed explanation-3: -Bomb: A pyroclast with a diameter greater than 64 mm (2.5 inches) and that has a rounded or ellipsoidal shape that indicates that it was wholly or partially molten during eruption and flight.

Detailed explanation-4: -Composite volcanoes, sometimes known as strato volcanoes, are steep sided cones formed from layers of ash and [lava] flows. The eruptions from these volcanoes may be a pyroclastic flow rather than a flow of lava. A pyroclastic flow is a superheated mixture of hot steam, ash, rock and dust.