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[pahy-ruh-klas-tik] /ˌpaɪ rəˈklæs tɪk/
adjective, Geology
composed chiefly of fragments of volcanic origin, as agglomerate, tuff, and certain other rocks; volcaniclastic.
Origin of pyroclastic
1885-90; pyro- + clastic Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2015.
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Examples from the web for pyroclastic
  • Above this coarse pumice-fall layer, layers of pyroclastic flow and tephra fall deposits record changes in the eruption.
  • pyroclastic surges are low-density versions of the pyroclastic flow.
  • pyroclastic flows can generate lahars by melting snow and ice.
  • The outer flanks of the asymmetrical pyroclastic shield volcano are formed by thick pyroclastic-flow deposits.
  • Dark streaks on pyroclastic-flow deposits are lahar deposits generated by rains.
  • Lower-density pyroclastic flows, called pyroclastic surges, can easily overflow ridges hundreds of feet high.
  • Gases, lava, and pyroclastic material are erupted from volcanic vents.
British Dictionary definitions for pyroclastic


(of rocks) formed from the solid fragments ejected during a volcanic eruption
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition
© William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins
Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
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Word Origin and History for pyroclastic

1887, from pyro- + clastic.

Online Etymology Dictionary, © 2010 Douglas Harper
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pyroclastic in Science
Composed chiefly of rock fragments of explosive origin, especially those associated with explosive volcanic eruptions. Volcanic ash, obsidian, and pumice are examples of pyroclastic materials.
The American Heritage® Science Dictionary
Copyright © 2002. Published by Houghton Mifflin. All rights reserved.
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