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 ...

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 ...

Devils Tower in Wyoming is surrounded by myths and mysteries. To the Sioux people, this site was sacred and some of their stories tell how this mountain formed: A long time ago a giant bear chased a ...

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 ...

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 ...

Both volcanic and plutonic rocks occur associated with the Martinsburg formation in Lebanon County. The area is located about one-half mile south of Jonestown and is approximately six and one-half ...

There are three types of rock found on Earth. These are igneous, metamorphic and sedimentary. Each rock type is formed in a different way. For example, the rock malachite is mostly made of the ...

Scientists on NASA's Perseverance mission made a surprising discovery about the composition of rock in Jezero Crater, one that will help them get a better idea of when water existed on Mars, and ...

Sedimentary rocks are made up of pieces of older rocks (igneous, metamorphic, and sedimentary) and organic remains (shells, bone, etc.). When rocks break apart from erosion they are transported by ...