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 ...

When you consider plate tectonics we often think of hot magma bubbling up from the Earth’s mantle, and we remember the vast assortment of pictures that we’ve seen–images featuring hundreds of active ...

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 ...

Introduction -- Physical properties of magma -- Intrusion of magma -- Forms of igneous bodies -- Cooling of igneous bodies and other diffusion processes -- Classification of igneous rocks -- ...

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 ...

You might not know it, but Ireland is dotted with extinct volcanoes that have shaped the island we know and love today ...

What’s hiding inside? Why Wyoming’s Devils Tower is still a geological mystery Standing tall at 1,267 feet in Northeastern ...