Study Guide Notes: Chapter 4 Unit Test OVERVIEW: Lesson 1: Rocks and the Rock Cycle (begins on p. 110) Geologists use texture and the composition of grains to classify types of rocks. Vocabulary: Rock – is a natural, solid mixture of minerals or grains. Grain – the fragments that make up rock. Texture – describes the size & arrangement of minerals or grains in a rock. Rock Types: (Igneous, Sedimentary, Metamorphic) Igneous Rocks – are rocks that form from cooling and crystalizing magma and lava. Magma – is molten or liquid underground rock. Lava – is molten rock that erupts onto Earth’s surface. Extrusive Rocks – are rocks formed on the surface of the Earth when volcanic material erupts, cools, and crystallizes. *(creating fine-grain texture) Intrusive Rocks – are rocks formed underground as magma slowly cools. *(creating large crystals) Sedimentary Rocks – are rocks formed from rock fragments and materials that include mineral crystals, or the remains of certain plants and animals. Compaction – occurs when the weight of layers of sediment forces out fluids and decreases the space between the grains of rocks. Cementation – occurs when minerals dissolved in water crystallize between sediment grains of rocks. Clastic – are types of Sedimentary rocks that made up of broken pieces of minerals and rock fragments. The broken pieces and fragments are called clasts. Conglomerate – rounded clasts that are formed by fast moving water. Breccia – are angular fragments that form clastic sedimentary rocks. Chemical – are rocks formed when minerals crystallize directly from water. *(ex., rock salt) Biochemical – are rocks formed by organisms or contains the remains of organisms. Metamorphic Rocks – are rocks that form from preexisting rock that react to extreme changes in temperature and pressure, or the addition of chemical fluids. Most of these rocks form deep within Earth. *This process affects the structure or composition of a rock in a solid state. *See other (separate study guide for more Metamorphic information) Rock Cycle – is a series of natural processes that change one type of rock into another type of rock. See diagram on page 115). *Note – the ovals represent processes and the rectangles represent materials.