Final answer:
During explosive volcanic eruptions, pyroclasts are shattered magma pieces that can range from fine ash to large boulders. They can form volcanic fragmental rocks or be part of fast-moving, destructive pyroclastic flows.
Step-by-step explanation:
During explosive volcanic eruptions, pyroclasts are solid fragments of rock that originate from the volcano as it forcefully ejects materials. These pyroclasts are essentially shattered magma pieces that can vary in size from fine ash to large boulders.
The eruptions that throw these materials into the air and environment are often violent and can impact large areas, depositing a layer of pyroclastic material over the landscape. The term 'pyroclastic' comes from the Greek meaning 'fire-broken' or 'fire-clast', signifying their fiery origin.
Pyroclasts can also form volcanic fragmental rocks when they settle and consolidate. This can include materials like tuff, which is a type of rock formed from volcanic ash and sometimes includes glass and pumice fragments.
Pyroclastic flows, which are fast-moving currents of hot gas and volcanic matter, can also contain pyroclasts. These flows can be extremely destructive, as was seen in historical eruptions like that of Mount Vesuvius in 79 AD, which buried the cities of Pompeii and Herculaneum.
Therefore, the correct answer to what happens to pyroclasts during explosive volcanic eruptions is that they are shattered magma pieces, thrown into the environment where they can eventually form various igneous rocks or be part of destructive pyroclastic flows.