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Rocks And the Rock Cycle The Rock Cycle Rock Cycle Rocks A mixture of minerals, mineraloids, glass, or organic matter. Three main types of Rock – Igneous – Metamorphic – Sedimentary The Rock Cycle The changing of rocks from one form to another by processes such as weathering, erosion, compaction, cementation, melting, and cooling. Igneous Rocks Igneous Rock The beginning of the Rock Cycle Igneous Rocks Starts as MAGMA… rock that has melted from pressure and heat in the Earth Pressure and heat build Magma rises to surface Comes out in Volcano as LAVA Intrusive Rocks form below Earth’s surface Cool slowly Large crystals form Examples – Granite – Diorite – Gabbro Vs. Extrusive Rocks form when lava cools on or near Earth’s surface Fast cooling Small crystals form Examples – Obsidian – Pumice – Basalt Intrusive Granite Notice the crystals The crystals are pieces of mineral Diorite Gabbro Extrusive Obsidian Rhyolite Pumice Basalt Scoria Andesite Three Compositions that effect Igneous Rock Types Basaltic Dense, heavy Dark Colored Rich in Fe, Mg Hawaii Granitic Andesitic Light Colored Halfway Lower Density between other Thick and Stiff two Lot of S, O Violent Eruption Igneous Rock Types Ingeous rocks Basaltic Andesitic Granitic Instusive Extrusive Instrusive Extrusive Instusive Extrusive Gabbro Basalt Scoria Diorite Andesite Granite Rhyolite Pumice Obsidian Basaltic Andesitic Granitic Metamorphic Rocks Metamorphic Rocks Rocks that have changed due to temperature and pressure increases or that undergo changes in composition Can be formed from: – Igneous Rocks – Sedimentary Rocks – Metamorphic Rocks Formation of Metamorphic Rocks Rocks beneath the surface under pressure and heat Once reach critical pt, rocks melt Or mineral grains are flattened New rocks formed by combination of processes Classification of Metamorphic Foliated When mineral grains flatten and line up in parallel bands – Slate – Gneiss Nonfoliated When no banding occurs during formation – Quartizite – Marble Before and After Shale Slate Before and After Granite Gneiss Before and After Sandstone Quartzite Before and After Limestone Marble The Rock Cycle Now Sedimentary Rocks Sedimentary Rocks Sediments and Sedimentary Rocks Sedimentary rock are made when sediments become pressed or cemented together or when sediments precipitate out of a solution Sediments are loose materials such as rock fragments, mineral grains, bits of plants and animals that have been moved by wind, water, ice, or gravity How they are made 1st wind and/or water erode existing rock 2nd wind, water, ice, or gravity move sediments to a new location 3rd new rocks are made by compaction or cementation The two C’s that make Sed. Rock Compaction: after erosion has moved sediment to new location, pressure from upper layers pushed down on lower layers and small sediments stick together Cementation: from large sediments, water socks through soil and rock and dissolves minerals (calcite, hematite, & limonite) these fill small spaces in-between and harden
