Pumice is an example of extrusive igneous rock. 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 ...

This week...another photo from Chile. Here we got a good ol' geologic puzzle...the kind you'd learn in an intro class. Here we can use the intuitive law of cross ...

POTASSIUM–ARGON age determinations have been carried out mainly on minerals with a high potassium content, particularly micas and potassium feldspars, found in intermediate to acid igneous rocks, but ...

Proceedings of the Royal Irish Academy. Section B: Biological, Geological, and Chemical Science, Vol. 65 (1966/1967), pp. 203-236 (39 pages) The Ardara granite pluton is made up of two intrusive units ...

THE potential of the potassium–argon technique in the dating of young rocks can be evaluated by applying it to intrusive igneous rocks which are well dated by conventional geological methods. Because ...

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 (volcanic ...

An igneous intrusion composed of gabbro and granodiorite, Zuma Rock is located in Niger state, Nigeria. Here’s why this rock of our forefathers is surrounded by myth and legends. 1. The rock catches ...

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, those ...