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Igneous Rocks

Igneous Rocks. By: Mrs. J Couch. What does igneous mean?. Igneous means “fire” in Latin. How do igneous rocks form?. Begin as magma; cools; and becomes a solid igneous rock. What is magma and how does it form?. Magma is hot, liquid rock. Forms when: -rock is heated -pressure is released

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Igneous Rocks

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  1. Igneous Rocks By: Mrs. J Couch

  2. What does igneous mean? • Igneous means “fire” in Latin.

  3. How do igneous rocks form? • Begin as magma; cools; and becomes a solid igneous rock

  4. What is magma and how does it form? • Magma is hot, liquid rock. • Forms when: • -rock is heated • -pressure is released • -rock changes composition

  5. What happens to magma when it cools at different rates? (what determines an igneous rock’s texture?) • More time to cool: (slow cooling magma) • -crystals have time to grow larger • -coarse texture (can see crystals in rock) • Less time to cool: (quickly cooled lava) • -crystals don’t grow • -fine grained (almost can’t see crystals or no crystals)

  6. Felsic- light colored igneous rocks that are less dense • Mafic-dark colored igneous rocks that are more dense

  7. How do intrusive rocks form? • -Magma pushes (intrudes) into rocks below Earth’s surface and cools • -Usually coarse grained (cools slowly with large, visible crystals) • -Ex. Stone Mtn. (a batholith-the largest of all igneous intrusive rocks)

  8. What are the characteristics of extrusive rocks? • -Magma erupts (extrudes/exits) onto Earth’s surface • -Common around volcanoes • -Lava cools quickly on Earth’s surface • -Very small or no crystals

  9. Examples: Can you tell which one is intrusive and which one is extrusive?

  10. Where can lava come to the surface of the earth? • -Volcanoes erupt • -Fissures-long cracks in Earth’s crust on ocean floor and on dry land

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