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Samuel Lasco June 17, 2003 ELED 305-01 Fredric Tarnow The Rock Cycle 1. Is sedimentary rock is a mineral? T or F 2. Is a mineral a rock? T or F 3. Dirt is soil? T or F 4. Igneous meaning formed from: a.) water, b.) fire. c.) air 5. Sediments were formed from: a.)Elmer’s glue, b.)Cemented together c.)silly putty 6. Metamorphic rocks are change by: a) heat and pressure, b.) gravity c.) water pressure 7. Please match the box: IGNEOUS SEDIMENTARY METAMORPHIC granite, slate, calcite, quartz, feldspar, mica, andesite, breccia, , schist, gneiss, marble, travertine ,silica, flint, jasper, mudstone, limestone 1 short answer: What are the 4 layers of earth? THERE ARE FOUR MAIN LAYERS THAT MAKE UP THE EARTH: 1. Inner Core - A mass of iron with a temperature of about 7000 degrees F. Although such temeratures would normally melt iron, immense pressure on it keeps it in a solid form. The inner core is approximately 1,500 miles in diameter. 2. Outer Core - A mass of molten iron about 1,425 miles deep that surrounds the solid inner core. Electrical currents generated from this area produce the earth's magnetic field. 3. Mantle - A rock layer about 1,750 miles thick that reaches about half the distance to the center of the earth. parts of this layer become hot enough to liquify and become slow moving molten rock or magma. 4. Crust - A layer from 4-25 miles thick consisting of sand and rock. 1 essay question: How does the rock cycle work? As you might expect - since most of the earth's surface is covered by water - molten material from inside the earth often breaks through the floor of the ocean and flows from fissures where it is cooled by the water resulting in the formation of igneous rocks. Some low grade metamorphism often occurs during and after the formation of the rock due to the intrusion of the material by the sea water. As the molten material flows from the fissure, it begins forming ridges adjacent to it. If we examine the rock cycle in terms of plate tectonics, as depicted in the figure above, we see that igneous rocks form on the sea floor as spreading ridges. As the rocks cool, and more magma is introduced from below, the plate is forced away from the spreading ridge, and acquires a sediment cover. As shown in the figure, in this case, the oceanic plate eventually "dives" under the adjacent continental plate. As the oceanic plate travels deeper, high temperature conditions cause partial melting of the crustal slab. When that occurs, the surrounding "country rock" (existing adjacent rock) is metamorphosed at high temperature conditions by the contact. The molten material is either driven to the surface as volcanic eruptions, or crystallizes to form plutonic igneous rocks. There are three basic types of rocks. They are sedimentary, igneous, and metamorphic .Weathering is the process by which rocks are broken down into rock particles. Weathering agents include wind, water, temperature changes, gravity, glaciers, and plant and animal activity. Erosion moves weathered rock particles from one place to another. Erosion agents are wind, running water, glaciers, gravity, and plant and animal activity. Rock sediments are deposited layer upon layer, sometimes under water, sometimes in cracks of rock and in other low- lying places. As the layers deepen, the weight of the upper, newer layers and any water that might be on top of them, press the sediments together very tightly. In time, the sediments can become cemented together into rock. Compaction and cementation are processes that press sediments together to form sedimentary rocks. Cementation sometimes occurs when pebbles are "cemented" to each other by calcium carbonate. Rocks formed this way are called conglomerates. Heat and pressure deep in the crust of the Earth causes rocks to melt and form magma (liquified, molten rock that is between the crust and the core of the Earth). Magma reaches the surface of the Earth through volcanic action or through cracks in the Earth's crust, to form igneous rocks. When magma is under the surface of the Earth, it is called lava .When it is on the surface and is cooled, it is called basalt .If the lava cools before it reaches the surface, the rock is dense and the molecules are close together. If it cools after it reaches the surface, the lava is lighter with air bubbles in it. The rate of cooling is the factor that makes the difference in the kind of rock that results. Cooling causes crystallization to occur. Crystallization is the lining up of molecules to form rocks and minerals with geometric shapes which have edges, corners, and flat surfaces. When broken, rocks of a crystalline nature break along the flat surfaces. Heat and pressure form metamorphic rocks. The elements in them are changed and crystallized. Rocks of any type may be affected by any of the processes described above. All rocks do not follow a given cycle. There are many "shortcuts" within the cycle. For example, metamorphic rock may be buried beneath the Earth and, through pressure and heat, can be changed to a different form of metamorphic rock. Sedimentary rocks often are weathered and become a different rock by being eroded and elsewhere combined with other sediments. Rocks are mostly heterogeneous .That is, they usually have more than one kind of mineral in them. One can observe different minerals in rocks by noticing differences in color, shape of particles, and crystal formation. SOME COMMON ROCKS LISTED BY TYPE IGNEOUS: obsidian, rhyolite, granite, diorite, andesite, breccia, gabbro, basalt METAMORPHIC: slate, schist, gneiss, marble, quartzite, SEDIMENTARY: sandstone gypsum, salt (halite), calcite, travertine ,silica, flint, jasper, mudstone, limestone There are more sedimentary rocks than other types of rock found on the surface of the Earth. But, there are probably many times more metamorphic and igneous rocks than sedimentary rocks under the surface of Earth.