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Objectives Identify 3 types of rocks and how they are classified. Determine how each type of rock is formed Definition A naturally occurring solid mixture of one or more minerals Did you know….. ths 5/6 That rocks occupy of the volume of Earth and account for 2/3rds of its mass? Three types of rocks Igneous Sedimentary Metamorphic Rocks are classified based on how they form Igneous Derived from the Latin word ignis, meaning “fire” Rocks that form when magma cools and crystallizes Examples: Granite, pumice, basalt, rhyolite, obsidian, gabbro Classifying igneous rocks Texture Extrusive igneous rocks ○ Form from molten material that has cooled and crystallized close to or on Earth’s surface ○ Contact with air or water causes material to cool rapidly ○ Fine-grained or small crystals ○ Ex. Pumice, basalt, rhyolite, obsidian Classifying igneous rocks Texture Intrusive igneous rocks ○ Magma that pushes into surrounding rocks and crystallizes underground ○ Cools slowly ○ Large, visible crystals, coarse grained ○ Contain mineral crystals (may contain valuable minerals and gemstones) Classifying igneous rocks Mineral Composition Granitic Composition Basaltic Composition Andesitic Composition Did you know… the oldest rocks are meteorites, more than 4.5 billion years old, which formed at the same time as earth? Sedimentary Rocks Recycled pieces that form new rock How is it done? Sedimentary rock formation Preexisting rock Weathering Weathering When rock gets broken into pieces by the effects of wind, water, ice, changing temperatures and gravity Two types of weathering Chemical weathering Physical weathering Sedimentary rock formation Sedimentary rock formation Deposition Occurs when the sediment eventually comes to rest on the ground or sinks to the bottom of bodies of water Layers will build up on top of one another Sedimentary rock formation Preexisting rock Weathering Sediments Erosion Deposition Compaction and cementation Compaction and Cementation New layers of sediment may be loosely packed with many air and H2O pockets The lower layers get squished together due to the weight and pressure of the layers above…this pushes out the water Compaction and Cementation The dissolved minerals in the water form crystals between the grains which holds them together Sedimentary rock formation Then the cycle begins again Sedimentary Rocks Examples Shale Sandstone Conglomerate (also called pudding stone) Soft coal Rock salt Features of Sedimentary Rocks Bedding Distinct horizontal layers Effects of wind, H20, the sun, and raindrops can be preserved Fossils Preserved remains or traces of organisms that once lived Mud cracks Ripple marks A joke… Where night? do fossils go to bed at Metamorphic Rock High temps and/or pressure Change the texture, mineral makeup or chemical makeup of a rock WITHOUT melting it. Metamorphic Rock Regional metamorphism When large areas of Earth’s crust are effected by high pressure and temperature Contact metamorphism When magma comes in contact with solid rock Hydrothermal metamorphism Hot H20 from volcanic activity