pyrochlastic

Pyrochlastic is an adjective that appears occasionally in geological texts, but it is not widely recognized as a distinct term in modern volcanology. In current scientific usage, the standard term is pyroclastic, derived from Greek pyro- “fire” and klastos “broken.” Pyroclastic describes fragments and deposits produced by explosive volcanic activity, including ash, pumice, lapilli, and the chaotic mixtures that form pyroclastic flows and tephra beds.

When pyrochlastic is encountered, it is generally treated as a misspelling or an archaic variant of pyroclastic rather than as a term with a separate technical meaning. If used, it may reflect historical spelling practices or non-specialist writing, but there is no widely accepted alternative definition that distinguishes it from pyroclastic in modern geology.

In formal writing, readers should prefer pyroclastic to ensure accuracy and clarity. The concept remains central to volcanology, encompassing the materials ejected during eruptions and the deposits they leave behind, such as ignimbrites, tuffs, and tephra layers. Related terms include tephra, pyroclastic flow, and pyroclastic deposit, which collectively describe the processes and products of explosive volcanic activity.