Quick Reference

A formation of rock made of magma which has erupted onto the earth's surface as lava and has then solidified. The crystals in extrusive rocks are small, since the lava solidifies rapidly, giving little time for crystal growth. Extrusions emerge from fissure eruptions and volcanoes. See Redfield et al. (2007) Geology 35, 11.

Subjects: Earth Sciences and Geography.

Reference entries