Transcript Rock cycle
Earth Science A study in Change: Rocks Watch for & It will tell you when/where information will be used in this unit! Rocks Any sold mass of minerals, or mineral like material. Inorganic solid, crystalline structure, definite chemical composition. Isn’t a rock, just a rock? So what? They aren’t static objects. They change with the earth and can tell us about it. Their timeline is just different than ours! Most Common Minerals (pg 35) Know these! Oxygen Silicon Aluminum Iron Calcium Sodium Potassium Magnesium Other Main Types of Rock Igneous Sedimentary Metamorphic Processes that change rock Melting & cooling Weathering & erosion Compaction & cementation Heat & Pressure Igneous Rocks Form from the cooling of magma or lava. Magma = molten rock below the surface of the earth (625oC or 1032oF, low end) Intrusive igneous rock Composed of silicon, oxygen, & gases like water vapor Lava = molten rock above the surface of the earth Extrusive igneous rock Similar in composition to intrusive igneous, without the gases (low pressure = escape) Igneous Characteristics Texture Course grained - large crystals caused by slow cooling of magma, usually intrusive Fine grained - small interlocking crystals due to relatively fast cooling Glassy - cools too quickly to form crystals, may appear glassy, may not (obsidian vs. pumice) Porphyritic - both large and small crystals due to varying rates of cooling Igneous Characteristics Composition Granitic - made up of mostly quartz or feldspar Tend to be light colored Basaltic- made up of mostly dark silicates, rich in magnesium and iron Tend to be dark colored Other - either a combination of the above or ultramafic (really old rocks) Igneous Rock Examples Obsidian Lava flow= basalt Porphyritic Granite Aphanitic Sedimentary Rocks Form when existing rocks are broken down into sediments and the sediments are cemented together to form a “new” (recycled) rock. Weathering - process by which existing rock is broken down. Physical weathering - breaking of a large rock into smaller pieces(physical changes) Chemical weathering - changing of rock composition due to chemical changes Processes Forming Sedimentary Rocks Weathering Ice wedging, root action, acid rain Faster when there is lots of water in environment Erosion - process by which weathered sediment is transported away from original parent rock. Wind, Water, Ice, Gravity Deposition - fancy term for when the eroded particles are dropped! Processes Forming Sedimentary Rocks Compaction - process of squeezing or smashing of deposited sediments into a smaller volume Usually due to the weight of new sediments being deposited above. Cementation - process of gluing sediments together Dissolved minerals precipitate out of solution and are deposited in the space between sediments. Classification of Sedimentary Rocks Clastic Sedimentary- composed of weathered sediments and minerals Conglomerate, sandstone, shale Bits and pieces stuck together. Looks or feels chunky Chemical Sedimentary - composed from precipitates of dissolved minerals Limestone, rock salt, gypsum(drywall) Sedimentary Rock Examples SandstoneClastic Limestone -Chemical Conglomerate - Clastic Metamorphic Rock Formed when existing rocks are changed by heat and pressure(causes chemical reactions). Heat - provides energy for chemical reactions Earth structure provides heat source Amount required to change a rock depends upon its mineral composition Chemical Reactions - hot water containing other substances that allow recrystallization Pressure - from all directions, affected by depth Types of metamorphic rock Foliated - layered or banded appearance of metamorphic rocks Due to parallel orientation of mineral crystals Forms when sedimentary rock is smashed Nonfoliated - does not have banded texture, usually made up of only one mineral. Metamorphic Rock examples Sandstone, before/after, nonfoliated Slate (parent = shale) foliated Metamorphic Examples Marble nonfoliated Quartzite nonfoliated Rock Cycle (final exam)