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pyroclastic




A term that describes any rock fragments thrown out by volcanic activity, generally in association with some violent explosive action. Pyroclasts normally include solidified lava left behind by a previous eruption of the volcano, as well as rocks from the crust, small pieces of cinders, ash, and dust. The largest pyroclastic fragments, known as volcanic bombs, weigh several tons. Smaller pieces are known as lapilli. When the pyroclastic activity stops, outpourings of lava often follow. Rocks formed by consolidation of these pyroclastic fragments, such as volcanic breccia and tuff, are also termed pyroclastic.


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   • GEOLOGY AND PLANETARY SCIENCE