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Igneous Rocks

Igneous Rocks. Igneous Rocks. Form from the crystallization of magma From Latin “ ignis ” which means fire Most common rocks in the Earths crust by far Two types of Igneous Rock. Extrusive. Cools quickly on the Earth’s surface Fine-grained Evidence

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Igneous Rocks

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  1. Igneous Rocks

  2. Igneous Rocks • Form from the crystallization of magma • From Latin “ignis” which means fire • Most common rocks in the Earths crust by far • Two types of Igneous Rock

  3. Extrusive • Cools quickly on the Earth’s surface • Fine-grained • Evidence • We can actually watch extrusive igneous rocks from as lava cools

  4. Intrusive • Cools slowly beneath the surface of the Earth • Coarse-grained (large/rough) • Evidence • Cross-cutting relationship with other rock formations

  5. Cross-cutting • Most igneous intrusive rocks have cross-cut something • Magma comes up through cracks in rocks • Magma the cools leaving an igneous intrusion • Granite is the most common intrusive igneous rock

  6. Magma • Not a pure substance • Usually contains • Molten rock • Gases • Mineral crystals • Contains the same elements found in the Earth’s crust • Most abundant compound is Silica (SiO4) • Found in almost all rocks

  7. Melting • Not all parts of magma melt at the same time • This concept is called partial melting

  8. Crystallization • Not all parts of magma crystallize (harden) at the same time • This concept is called fractional crystallization • Harder substances (diamonds) harden at the same time and are harder to melt • Pressure causes substances to have different melting points

  9. Bowen’s Reaction Series • Shows the relationship between cooling magma and mineral formation

  10. Mineral composition • Again silica is the primary component of magma • Felsic rocks contain high levels of silica • Resistant to flow • Granite, Obsidian • Mafic rocks contain low levels of silica • “watery stew” • Gabbro, Basalt

  11. Uses • Interlocking grain textures make them very strong • They are also highly resistant to weathering • These characteristics make Igneous rocks excellent building materials.

  12. Sedimentary rocks

  13. Sedimentary Rocks • Composed of small pieces of rocks that have been broken down and deposited • Wind, water, and other forces transport sediments to sedimentary basins which can be more than 8 km thick.

  14. Clastic sediments • Boulder > 256 mm • Cobble 256 - 64 mm • Pebble 64 - 2 mm • Sand 2 – 0.062 mm • Silt 0.062 – 0.0039 mm • Clay < 0.0039 mm

  15. Buried Sediments experience high pressure and temperature • This causes lithification, which is the process of sediments turning into rock • Sedimentary rocks can also form from cementation • Sediments are cemented together by mineral growth

  16. Sedimentary Uses • Evidence of past events and life • Due to the presence of fossils • Energy sources • Oil • Natural gas • Coal

  17. Metamorphic rocks

  18. Metamorphic Rocks • From the Greek “meta” meaning change, and “morphe” meaning form • Rock is buried and experiences great pressure and temperature, but doesn’t quite melt • Very common in “mountain-building” areas • During metamorphism, rocks change form while remaining solid

  19. Types of metamorphic rock • Foliated • Minerals with flat needle-like structures line up in wavy layers and bands • Non-foliated • Mineral grains lack the flattened structure

  20. Rock Cycle • The remaking of rocks

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