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What are Igneous Rocks?

What are Igneous Rocks?. Chapter 5.1. Formation of Igneous Rock Magma – molten rock beneath the Earth’s surface. Lava – magma that flows out onto the Earth’s surface. Igneous rock forms when lava or magma cools and the minerals within it crystallizes. Magma consists mainly of the elements –

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What are Igneous Rocks?

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  1. What are Igneous Rocks? Chapter 5.1

  2. Formation of Igneous Rock Magma – molten rock beneath the Earth’s surface. Lava – magma that flows out onto the Earth’s surface. Igneous rock forms when lava or magma cools and the minerals within it crystallizes. Magma consists mainly of the elements – oxygen silicon aluminum iron magnesium calcium potassium sodium Magma is classified by the amount of silica (SiO4) it contains. - Silica content affects melting temperature and the thickness (viscosity) of the magma.

  3. Bonus Questions! 1. What is the difference between magma and lava? 2. What determines the melting point and thickness of magma?

  4. Magma Formation • Magma is formed when rock is melted within the Earth. • Factors affecting the formation of magma are: • Temperature • Pressure • Water content • Type of minerals present

  5. Bonus Question! 3. Name two factors affecting the formation of magma?

  6. Classification of Igneous Rocks Chapter 5.2

  7. Intrusive Igneous Rocks - form when magma cools slowly within the Earth’s crust. - form rocks with large crystals (coarse-grained). (magma cools slow enough for crystals to grow large) Granite

  8. Extrusive Igneous Rocks - form when lava cools quickly on the Earth’s surface. - form rocks with small crystals (fine-grained). (lava cools too quickly for large crystals to form) Basalt Pumice Obsidian

  9. Bonus Questions! 4. Give an example of an intrusive igneous rock. 5. Give an example of an extrusive igneous rock. 6. Which type of igneous rock has smaller crystals?

  10. Igneous Rocks as Resources Veins – as the last of the molten minerals (usually quartz) begin to crystallize, they are often squeezed into cracks in the rock to form veins. - some of the veins contain metallic elements (gold, silver, copper) that can be mined for a profit. Pegmatites – veins of extremely large-grained crystals. Pegmatite with blue corundum crystals (Wikipedia)

  11. Bonus Question! 7. What mineral deposit is gold usually associated with?

  12. Igneous Rocks as Resources Kimberlites – vertical intrusions of hardened magma (like the neck of a volcano). - well known for the diamonds they often contain. Construction Resources – since igneous rocks are strongand weather-resistant making them a great building material. Hewn kimberlite core sample from the James Bay Lowlands region of Northern Ontario, Canada. Green olivine grains and purplish red garnet are visible. The sample is 13 cm (5 inches) long. (Wikipedia)

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