After which type of natural disaster would pyroclastic flow most likely occur?

A pyroclastic flow (also known scientifically as a pyroclastic density current) is a fast-moving current of hot gas and rock (collectively known as tephra), which reaches speeds moving away from a volcano of up to 700 km/h (450 mph). The gas can reach temperatures of about 1,000 °C (1,830 °F). Pyroclastic flows normally hug the ground and travel downhill, or spread laterally under gravity. Their speed depends upon the density of the current, the volcanic output rate, and the gradient of the slope. They are a common and devastating result of certain explosive volcanic eruptions.

The word pyroclast is derived from the Greek πῦρ, meaning "fire", and κλαστός, meaning "broken in pieces". A name for some pyroclastic flows is nuée ardente (French, "burning cloud"); this was first used to describe the disastrous 1902 eruption of Mount Pelée on Martinique. In the dark, these pyroclastic flows glowed red.