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IGNEOUS ROCKS

Learn about the formation, texture, composition, and structures of igneous rocks. Explore the differences between extrusive and intrusive rocks, as well as various textures and compositions. Discover different types of igneous rock structures such as batholiths, laccoliths, stocks, dikes, sills, and volcanic necks.

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IGNEOUS ROCKS

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  1. IGNEOUS ROCKS

  2. IGNEOUS ROCKS • Igneous rocks are formed from molten material. - The term igneous is derived from Latin term meaning “from FIRE”!!

  3. IGNEOUS ROCKS ENVIRONMENT A. Extrusive igneous rocks are formed when molten rock cools above ground. Usually they are formed after the material has been erupted by a volcano. This molten material cools quickly. No crystals are visible to the eye.

  4. Intrusive igneous rocks are formed when molten rock cools below ground. These rocks cool very slowly. There is lots of time for visible crystals to grow

  5. EXTRUSIVE INTRUSIVE Cools slowly Cools quickly Cools below ground Cools above ground Visible crystals No visible crystals

  6. IGNEOUS ROCKS TEXTURE • Coarse: • INTRUSIVE igneous rock composed of large mineral grains. • GRANITE

  7. IGNEOUS ROCKS TEXTURE • Fine: • EXTRUSIVE igneous rock composed of fine-grained minerals. • BASALT

  8. IGNEOUS ROCKS TEXTURE • Glassy: • HIGHLY VISCOUS, silica-rich magma cools rapidly, no crystals. • OBSIDIAN

  9. IGNEOUS ROCKS TEXTURE • Vesicular: • HIGHLY VISCOUS, large amount of dissolved gases, rock full of holes. • PUMICE

  10. IGNEOUS ROCKS COMPOSITION • Mafic: • Low silica • Rich in Iron and Magnesium • DARK COLOR. • BASALT

  11. IGNEOUS ROCKS COMPOSITION • Felsic: • High silica • LIGHT COLOR. • RHYOLITE

  12. IGNEOUS ROCKS Igneous Rock Structures • Intrusions vs. Extrusions: - Form Underground - Form on the surface of the Earth

  13. IGNEOUS ROCKS INTRUSIONS • Batholiths: • At least 100 km2 of surface exposure. • Means “Deep Rock” • Sierra Nevada Mountains

  14. Exposed Batholiths

  15. IGNEOUS ROCKS INTRUSIONS • Laccoliths: • Flat-bottom intrusion that pushes over-lying rock layers into an arc. • Means “Lake of Rock” • Black Hills • South Dakota

  16. IGNEOUS ROCKS INTRUSIONS • Stocks: • Like a Batholith, but covers less than 100 km2. • Devils Tower • Wyoming

  17. IGNEOUS ROCKS INTRUSIONS • Dikes: • Igneous intrusion that cuts across rock layers. • Black Canyon • Colorado

  18. IGNEOUS ROCKS INTRUSIONS • Sills: • Hardened magma formed between parallel layers of rock. • Salisbary Crags • Scotland

  19. IGNEOUS ROCKS EXTRUSIONS • Volcanic Necks: • Solidified central neck of a volcano. • Shiprock • New Mexico

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