pyroclastic

About 0.21 uses per million words.

Meaning

1. adjective Mostly composed of rock fragments of volcanic origin or comminuted during an eruption.
2. noun A rock mostly composed of rock fragments of volcanic origin.

Similar words

subaqueous volcanoclastic volcaniclastic pyrometamorphic clastic vitroclastic fragmentary subvolcanic glomeroporphyritic platy

Often followed by

flows rocks flow material deposits materials debris and rock surge