6.1: Prelude to Metamorphic Rocks

Figure \(\PageIndex{1}\): Painted Wall of Black Canyon of the Gunnison National Park, Colorado, made of 1.7 billion-year-old gneiss intruded by younger pegmatites.

Metamorphic rocks, meta- meaning change and –morphos meaning form, is one of the three rock categories in the rock cycle (see Chapter 1). Metamorphic rock material has been changed by temperature, pressure, and/or fluids. The rock cycle shows that both igneous and sedimentary rocks can become metamorphic rocks. And metamorphic rocks themselves can be re-metamorphosed. Because metamorphism is caused by plate tectonic motion, metamorphic rock provides geologists with a history book of how past tectonic processes shaped our planet [1].

Figure \(\PageIndex{1}\): Rock cycle showing the five materials (such as igneous rocks and sediment) and the processes by which one changes into another (such as weathering). (Source: Peter Davis)

Reference

1. Yardley BWD (1989) An introduction to metamorphic petrology. Prentice Hall