You Rock! Well… at least the Earth Rocks! 1 How Rocks Form 2 Igneous Rocks 3 Sedimentary Rocks 4 Metamorphic Rocks

How Rocks Form VOCABULARY In general, a rock is a group of minerals bound together. rock igneous magma Igneous, sedimentary, and metamorphic rocks are formed, broken down, and reformed in a recurring process called the rock cycle. sedimentary sediment metamorphic rock cycle click image to enlarge

6.2 Igneous Rock VOCABULARY Igneous rocks form as molten rock solidifies, as magma deep in the crust or lava at Earth’s surface cool. felsic mafic pluton Felsic magmas form light-colored, silica-rich rocks. Mafic magmas form dark-colored rocks rich in iron and magnesiums. batholith Igneous rock texture depends mainly on the rate at which magma or lava cools. Granite is igneous rock formed from felsic magma. Basalt is igneous rock formed from mafic magma.

6.2 Igneous Rock VOCABULARY Igneous rocks are grouped into families by mineral composition and texture. felsic mafic pluton Texture coarse- grained fine- glassy porous Chemical Composition felsic ultramafic felsic- intermediate mafic batholith granite granodiorite diorite gabbro peridotite, dunite, pyroxenite rhyolite andesite basalt obsidian basalt glass most pumice scoria diabase

6.2 Igneous Rock VOCABULARY Magma that solidifies underground forms various types of igneous intrusions. felsic mafic pluton Volcanic neck Laccolith batholith Volcano Stock Dike Sill Batholith

Sedimentary Rock VOCABULARY Sedimentary rocks form from sediments that result from weathering and erosion of rock at Earth’s surface. They often occur in layers, formed over time as different sediments are deposited on top of each other. cementation stratification fossil

Sedimentary Rock VOCABULARY Sedimentary rocks are grouped by the type of sediment from which they form: clastic, chemical, or organic. cementation stratification fossil Clastic: Sandstone Chemical: Rock Salt Flat Organic: Limestone Cliffs

6.3 Sedimentary Rock VOCABULARY Clastic sediments are often sorted by water action before pressure and mineral cements turn them into rock. cementation stratification fossil 1. A river moves sediment into a lake. 2. Particles are sorted by size. The largest gravels are the first to be deposited, followed by sands, and then silt and clay. Sands and Gravels Sands Silt and Clay 3. Over time, the sediments are buried, compacted, and may be cemented. Conglomerate Sandstone Shale

Sedimentary Rock VOCABULARY Clastic sediments are often sorted by water action before pressure and mineral cements turn them into rock. cementation stratification fossil Fossils, ripple marks, mud cracks, nodules, concretions, and geodes features associated with sedimentary rocks.

6.4 Metamorphic Rock VOCABULARY Metamorphic rocks form when heat or pressure or both alter parent, or preexisting, rocks. parent rock metamorphism deform Shale Slate becomes becomes Phyllite Schist becomes

6.4 Metamorphic Rock VOCABULARY Metamorphic rocks form when heat or pressure or both alter parent, or preexisting, rocks. parent rock metamorphism deform Metamorphism can occur across a region, as in mountain building events, or it can occur in smaller local areas. A metamorphic rock may be described and identified according to its parent rock, mineral composition, and texture.