Photograph of compositionally-layered gneiss outcrop southeast of San Gorgonio Mtn in the San Bernardino Mountains, southern California (Section 16 of T.1S., R.2E.); pencil is about 6 inches (15 cm) long. This outcrop shows metamorphic rocks that look considerably different today than when the geologic materials first were formed. The rocks began life either as sedimentary materials deposited in a marine environment, or as igneous materials of granitic composition.
Whatever their original origin, the parent rock (protolith) was subjected to high temperatures and strong directed forces (stress) that reconfigured the original mineral components into the conspicuous dark- and light-colored (mafic and felsic) layers that characterize the outcrop. This mineral segmentation into discrete layers is a type of foliation that geologists refer to as gneissose layering, and the rock generally is called "gneiss". Note the contortion of the mafic and felsic layers into small folds. Photo by J.C. Matti, USGS, June, 1978.
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Despite these uncomfortable conditions, metamorphic rocks do not get hot enough to melt, or they would become igneous rocks!