pyroclastic

Etymology

From pyro- + clastic, from Ancient Greek πῦρ (pûr, “fire”), and κλαστός (klastós, “broken”).

adj

1. (volcanology) Mostly composed of rock fragments of volcanic origin or comminuted during an eruption.
   The word "ash" is not a very good one to include all the mechanical accompaniments of a subaerial or subaqueous eruption, since ash seems to be restricted to a fine powder, the residuum of combustion. A word is wanting to express all such accompaniments, no matter what their size or condition may be, when they are accumulated in such mass as to form beds of "rock." We might call them perhaps "pyroclastic materials," ... 1862, Joseph Beete Jukes, “Igneous Rocks”, in The Student's Manual of Geology, 2nd edition, Edinburgh: Adam and Charles Black, page 68
   Within sixty seconds, the entire area was razed by pyroclastic material with a temperature of nearly two thousand degrees Fahrenheit. 2022, Lindsey Fitzharris, The Facemaker, page 61

noun

1. A rock mostly composed of rock fragments of volcanic origin
   The basic volcanics are altered andesites, porphyritic diabases and andesites, and various pyroclastics. 1897, “General Notes: Geology and Paleontology”, in Edward D. Cope, Frederick C. Kenyon, editors, The American Naturalist: An Illustrated Magazine of Natural History, volume 31, Philadelphia: The Edwards & Docker Co., No. 363, page 221