We often talk about climate change, melting glaciers, or strange landforms. But we rarely think about something that’s always ...

The word extrusive means that the magma was forced onto the earth's surface and cooled in a matter of hours. Granite is an example of intrusive igneous rock.

Igneous rocks are formed when molten rock (magma) cools and solidifies, with or without crystallization, either below the surface as intrusive (plutonic) rocks or on the surface as extrusive ...

Extrusive igneous rocks are formed by magma that has erupted onto the surface as lava and then cooled quickly. Obsidian is an example of an extrusive igneous rock.

In my last column, I wrote about the locations where you can find igneous rocks that were formed from lava. The metarhyolite and metabasalt described in the column are known as extrusive rocks ...

It is formed by cooling and crystallizing magma that has been melted in volcanoes, or from the melted rock that is still inside the crust. During the solidification process, that makes volcanic rock, ...

According to the seismologists, this suggests that entire oceanic slabs – up to 62 miles (100 kilometers) thick – carry significant amounts of the extrusive igneous rock as they descend ...

University of Hawaii ‑ SOEST. "Extrusive volcanism formed the Hawaiian Islands." ScienceDaily. ScienceDaily, 7 October 2013. <www.sciencedaily.com / releases / 2013 / 10 / 131007094558.htm>.

O. F. Tuttle, Origin of the Contrasting Mineralogy of Extrusive and Plutonic Salic Rocks: A Reply, The Journal of Geology, Vol. 61, No. 3 (May, 1953), pp. 278-280 ...

Lunar igneous activities, including intrusive and extrusive magmatism, and their products contain significant information about the lunar interior and its thermal state. Their distribution is ...