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 ...

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 ...

Igneous rocks contain randomly arranged interlocking crystals. The size of the crystals depends on how quickly the molten magma solidifies and can form extrusive igneous rocks or intrusive igneous ...

being the only place on earth where rocks from the earth’s mantle (6 km below the ocean floor) are being actively exposed above sea-level. These unique exposures include excellent examples of pillow ...