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Download Introduction to Rocks - Red Hook Central Schools
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You Rock! Well… at least the Earth Rocks! 1 How Rocks Form 2 Igneous Rocks 3 Sedimentary Rocks 4 Metamorphic Rocks VOCABULARY rock igneous magma sedimentary sediment How Rocks Form In general, a rock is a group of minerals bound together. Igneous, sedimentary, and metamorphic rocks are formed, broken down, and reformed in a recurring process called the rock cycle. metamorphic rock cycle click image to enlarge VOCABULARY felsic mafic pluton batholith 6.2 Igneous Rock Igneous rocks form as molten rock solidifies, as magma deep in the crust or lava at Earth’s surface cool. Felsic magmas form light-colored, silica-rich rocks. Mafic magmas form dark-colored rocks rich in iron and magnesiums. 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 felsic mafic pluton batholith Igneous rocks are grouped into families by mineral composition and texture. Chemical Composition Texture coarsegrained felsic granite felsicintermediate granodiorite intermediate diorite mafic gabbro ultramafic peridotite, dunite, pyroxenite finegrained glassy porous rhyolite obsidian most pumice andesite diabase basalt basalt glass scoria VOCABULARY felsic mafic 6.2 Igneous Rock Magma that solidifies underground forms various types of igneous intrusions. pluton batholith Volcanic neck Laccolith Volcano Stock Dike Sill Batholith VOCABULARY cementation stratification fossil Sedimentary Rock 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. VOCABULARY cementation stratification fossil Sedimentary Rock Sedimentary rocks are grouped by the type of sediment from which they form: clastic, chemical, or organic. Clastic: Sandstone Chemical: Rock Salt Flat Organic: Limestone Cliffs VOCABULARY cementation stratification fossil 6.3 Sedimentary Rock Clastic sediments are often sorted by water action before pressure and mineral cements turn them into rock. 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 Conglomerate Sandstone Silt and Clay Shale 3. Over time, the sediments are buried, compacted, and may be cemented. VOCABULARY cementation stratification fossil Sedimentary Rock Clastic sediments are often sorted by water action before pressure and mineral cements turn them into rock. Fossils, ripple marks, mud cracks, nodules, concretions, and geodes features associated with sedimentary rocks. VOCABULARY parent rock metamorphism 6.4 Metamorphic Rock Metamorphic rocks form when heat or pressure or both alter parent, or preexisting, rocks. deform becomes Shale becomes Slate becomes Phyllite Schist VOCABULARY parent rock metamorphism deform 6.4 Metamorphic Rock Metamorphic rocks form when heat or pressure or both alter parent, or preexisting, rocks. 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.
