I would like to know a definition of the words: Hyaloclastic,agglomerate,breccia and dolerite. I am researching a web page on the volcanic history of Great Britain and I need to know what these words mean.

David

Hyaloclastite: A deposit formed by the flowing or intrusion of lava or magma into water, ice, or water-saturated sediment, and its consequent granulation or shattering into small angular fragments. Agglomerate: A term for a chaotic assemblage of coarse angular pyroclastic material. Also called volcanic breccia. Breccia:A coarse-grained clastic rock composed of angular broken rock fragments held together by mineral cement or a fine matrix. Dolerite:A fine-grained intrusive rock made of labradorite and pyroxene with an ophitic texture. In England the word is used for weathered basalt. Sources of definitions: Bates, R.L., and Jackson, J.A., Glossary of Geology (American Geological Institute, 1987)

Sincerely,
Steve Mattox

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