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Rocks What is a rock? a. Naturally occurring b. Solid c. Made of two or more minerals. Composed mostly of these eight elements: Oxygen-O; Silicon-Si; Aluminum-Al; Iron-Fe; Calcium-Ca; Sodium-Na; Potassium-K; Magnesium-Mg d. Their classification is based on how they were formed. What is a mineral? Is naturally occurring Is a solid Is inorganic Has a fixed chemical formula Has an orderly crystalline structure Over 4000 minerals! But only eight groups commonly found in earth’s rocks. Rock Types by Formation a. Igneous 1. 2. 3. Temperatures in lower crust and upper mantle melt rock into magma. Approximately 1400 degrees C. This liquid is less dense than solid rock so it rises. As the magma rises, magma cools and hardens to form igneous rocks. Rock Types by Formation b. Sedimentary (most common) 1. Sediments, small pieces of rock, shells and other organic material are carried by wind or water and deposited. 2. As layers of sediment deposit on top of each other they are compacted and cemented into sedimentary rock. Rock Types by Formation c. Metamorphic 1. a result of changes that occur to existing rocks. 2. Changes are caused by high heat, pressure, or by chemical reactions. The Rock Cycle Rock Cycle The rock cycle shows how the three rock types relate to each other. Rock Cycle There are 4 processes of rock formation that are the links between the rock types, sediment and magma. weathering, crystallization, lithification metamorphism Weathering is the gradual wearing down of all rock types once they are exposed at the surface. Crystallization is the cooling of magma to form an igneous rock. Lithification is the transformation of loose sediment into a rock by a slight heating and/or cementation. Metamorphism occurs when a rock is subjected to heat and pressure, transforming a rock. This can occur on any rock, even a metamorphic rock. Fig. 2.9 MAGMA IGNEOUS Crystallization MAGMA 14 IGNEOUS Plutonic Crystallization MAGMA 15 Volcanic IGNEOUS Plutonic Crystallization MAGMA 16 Weathering Volcanic IGNEOUS Plutonic Crystallization Uplift MAGMA 17 Weathering SEDIMENT Volcanic IGNEOUS Plutonic Crystallization Uplift MAGMA 18 Weathering SEDIMENT Erosion & Transport Volcanic IGNEOUS Plutonic Crystallization Uplift MAGMA Water Wind Ice Gravity 19 Weathering Volcanic SEDIMENT Lithification = Cementation + Compaction IGNEOUS Erosion Transport Deposition SEDIMENTARY Plutonic Crystallization Uplift MAGMA 20 Weathering SEDIMENT Erosion Transport Deposition Volcanic SEDIMENTARY IGNEOUS Plutonic Increased P&T METAMORPHIC Crystallization Burial Uplift MAGMA 21 SEDIMENT Weathering Erosion Transport Volcanic Can you see IGNEOUS any shortcuts? Deposition SEDIMENTARY Plutonic Increased P&T METAMORPHIC Crystallization Melting Burial Uplift MAGMA 22 Weathering SEDIMENT Erosion Transport Deposition Volcanic SEDIMENTARY IGNEOUS Plutonic Increased P&T METAMORPHIC Crystallization Melting Burial Uplift MAGMA 23 In Conclusion… • The rock cycle demonstrates the relationships among the three major rock groups • It is powered by the interior heat of the Earth • As well as earth’s momentum and… • The energy from the sun • It involves processes on the Earth’s surface as well as the Earth’s interior • It connects the “hydrologic cycle” with the “tectonic cycle”.