Final answer:
The pyroclastic stage was part of the volcanic eruption of Mount Vesuvius in 79 AD, involving rapid, hot flows of gas and matter that destroyed and preserved Pompeii and Herculaneum.
Step-by-step explanation:
The pyroclastic stage refers to a phase of a volcanic eruption characterized by the emission of pyroclastic flows, which are fast-moving currents of hot gas and volcanic matter (such as ash, pumice, and volcanic rocks). One of the most noteworthy instances of this occurred during the eruption of Mount Vesuvius in 79 AD, which devastated the ancient cities of Pompeii and Herculaneum. These pyroclastic flows began on the night of August 24 or early the next day, August 25, and resulted in the incineration or suffocation of those who had not evacuated, as well as the preservation of organic material and non-organic artifacts due to the intense heat and rapid sedimentation.