Eruptions on the islands of Santorini in Greece and Krakatau in Indonesia resulted in:

A) collapse of a huge caldera that caused part of an island to disappear beneath the sea
B) a huge ash column and pyroclastic flows
C) destructive waves that traveled across the sea
D) all of these

Caldera

A vast volcanic depression, usually created when land collapses after a volcanic explosion.

Pyroclastic Flows

Fast-moving current of hot gas and volcanic materials that move away from a volcano during an explosive eruption.

Ash Column

A large plume of volcanic ash that is ejected into the atmosphere during a volcanic eruption.