volcanic rock

Other forms: volcanic rocks

Definitions of volcanic rock

1. noun

   extrusive igneous rock solidified near or on the surface of the Earth
   types:

   agglomerate

   volcanic rock consisting of large fragments fused together

   amygdaloid

   volcanic rock in which rounded cavities formed by expanding gas have subsequently become filled with mineral deposits

   dacite

   a grey volcanic rock containing plagioclase and quartz and other crystalline minerals

   basalt

   the commonest type of solidified lava; a dense dark grey fine-grained igneous rock that is composed chiefly of plagioclase feldspar and pyroxene

   volcanic glass

   a kind of natural glass produced when molten lava cools very rapidly

   lava

   rock that in its molten form (as magma) issues from volcanos; lava is what magma is called when it reaches the surface

   tufa, tuff

   hard volcanic rock composed of compacted volcanic ash

   obsidian

   acid or granitic glass formed by the rapid cooling of lava without crystallization; usually dark, but transparent in thin pieces

   pitchstone

   dark acid granitic glass

   tachylite

   a basic or basalt glass

   aa

   a dry form of lava resembling clinkers

   pahoehoe

   freely flowing lava

   pillow lava

   lava that hardened in rounded shapes suggestive of pillows; believed to result from underwater eruptions

   type of:

   igneous rock

   rock formed by the solidification of molten magma