Coastal & Marine Geology InfoBank

USGS CMG InfoBank: Crystallized Minerals


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Comment: 12:07 - 12:38 (00:31)

Source: Annenberg/CPB Resources - Earth Revealed - 14. Intrusive Igneous Rocks

Keywords: plutonic, intrusion, mafic, felsic, crystal, "lava flow", ash, magma

Our transcription: Geologists find evidence of differentiation preserved in many plutonic rocks.

For example, some intrusions are layered due to settling out of early forming mafic minerals.

As these minerals left the upper part of the magma body, only felsic minerals were left to crystallize there.

At volcanoes, the composition of lava and ash may change in time reflecting differentiation in the magma underneath.

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U.S. Department of the Interior \| U.S. Geological Survey URL: http://walrus.wr.usgs.gov/infobank/programs/html/school/moviepage/13.01.13.html Page Contact: InfoBank staff Page Last Modified: Wed Aug 27 06:15:23 PDT 2008 (wcs)