The topics covered in this chapter can be summarized as follows:
6.1 What Is a Rock?
A rock is a cohesive aggregate of minerals. It may consist of many grains of the same mineral, or grains of different minerals.
6.2 The Rock Cycle
The three types of rocks are igneous, formed from magma; sedimentary, formed from fragments of other rocks or precipitations from solution; and metamorphic, formed when existing rocks are altered by heat, pressure, and/or chemical action. The rock cycle summarizes the processes that contribute to cycling of rock material among these three types. The rock cycle is driven by Earth’s internal heat, and by processes happening at the surface, which are driven by solar energy.
Questions for Review
1. What processes must take place to transform rocks into sediment?
2. What processes normally take place in the transformation of sediments to sedimentary rock?
3. What are the processes that lead to the formation of a metamorphic rock?