Adense mix of dry, hot rock fragments and hot gas erupting from volcanic vents at high speed is
pyroclastic flow.
lahar.
fumarole.
tephra.

Answer : Option A) Pyroclastic Flow.

Explanation : A dense mix of dry, hot rock fragments and hot gas erupting from volcanic vents at high speed is called as Pyroclastic Flow.

A pyroclastic flow is a fast-moving current of hot gas and volcanic matter which is collectively known as tephra that moves away from a volcano it is also known as a pyroclastic density current or a pyroclastic cloud. It has a speed of about 100 km/h on average but can reach to the speed of 700 km/h. The gases can reach temperatures involved in the flow are of about 1,000 °C .

Pyroclastic flows are a very common and are considered to be devastating, as they are result of certain explosive eruptions; which normally touch the ground and hurtle downhill, or spread laterally under gravity. The speed of the flow depends upon many factors such as; the density of the current, the volcanic output rate, and the gradient of the slope.

b. examine and describe cells

the answer is option a.