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Download Rocks - Duplin County Schools
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Rocks 3.1 The Rock Cycle Igneous Rocks • Form from the solidification of melted minerals (magma or lava). – Magma = melted rock underground – Lava = melted rock aboveground • Extrusive Igneous Rocks – Rocks formed from hardened lava. – Quick cooling results in extrusive igneous rocks with finegrained or glassy textures. • Intrusive Igneous Rocks – Rocks formed from hardened magma. – Slow cooling results in intrusive igneous rocks with coarsegrained textures. Sedimentary Rocks Sedimentary rocks may be made of rock fragments—sediments—or by chemical reactions. The classification of sediments is shown below. 3 Types of Sedimentary Rock • Clastic – Sedimentary rocks made of cemented sediments. • Chemical – Form from chemical precipitation. When minerals settle out from a solution, they come together to form chemical rocks. • Organic – Rocks that come from the remains of organic matter. A good example is coal. Clastic Chemical Organic Metamorphic Rocks • Formed when heat and pressure changes existing rock. • This can be done 2 ways: • Contact Metamorphism (heat driven) – when magma intrudes into a previously existing rock layer, and “bakes” the surrounding rock. • Regional Metamorphism (pressure driven) – when intense pressure is applied to previously existing rock. Is driven by plate tectonics. Contact Metamorphism Contact Metamorphism Previously Existing Rock Contact Metamorphism Cont… Regional Metamorphism Pressure Pressure Types of Metamorphic Rocks Foliated • Have a banded appearance. Non-Foliated • No banded appearance.
