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Igneous Rock Classification

Igneous Rock Classification. Dr. David Steer. Rock cycle. Analysis Time. Given: Bag rocks. Group these rocks in some manner. Grouping items. Color (Proxy for silica content). Size (Proxy for grain size). Group these objects in some logical way. Grouping items.

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Igneous Rock Classification

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  1. Igneous Rock Classification Dr. David Steer

  2. Rock cycle

  3. Analysis Time • Given: • Bag rocks Group these rocks in some manner

  4. Grouping items Color (Proxy for silica content) Size (Proxy for grain size) • Group these objects in some logical way.

  5. Grouping items • Group these objects in some logical way.

  6. Analysis time • Given: • Bag rocks Group these rocks in some manner

  7. Rock Cycle

  8. Igneous Rocks • Volcanic (extrusive) igneous rocks • Cool fast, small crystals • form when molten rock (magma) in the earth’s interior rises to the surface through pipes or fractures in the crust.

  9. Igneous Rocks • Plutonic (intrusive) igneous rocks • Cool slow, large crystals • form when magma cools within the earth. Igneous rocks that cool below the earth's surface are termed plutonic (or intrusive) igneous rocks.

  10. Classification of Igneous rocks • Texture size of crystals most important • Cooling rates • Surface, fast • Small crystals • Below surface slow • Larger crystals Which formed at surface? Both are the same chemistry a) b) Rhyolite Granite

  11. Chemical Composition • Color • Indicative of chemistry and temperatures of formation • Dark colors • High temperatures (1000 to 1200 oC) • Low silica content • Light colors • Lower temperatures • High silica content Which is the high silica rock? Both formed below the surface a) b) Gabbro Granite

  12. Texture • So explain this!!!!

  13. Six common Igneous Rocks 1000 C Solidifying Temperature 500 C Increasing Grain Size Lighter Color

  14. Draw a concept map that guides you through classifying an igneous rock. Use these terms to: Classify Igneous Rocks Basalt Color Cool Quick Cool Slow Dark Extrusive Gabbro Granite High Silica Large Grain Low Silica Light Plutonic Texture Rhyolite Small Grain

  15. Identify the rock type associated with the diagram below. Question • Plot 1 • Plot 2 • Plot 3 • Plot 4 • andesite porphory • gabbro • basalt • obsidian

  16. 5) Imagine that all minerals found in rocks were the same color. What information would you no longer be able to infer?a. texture b. cooling ratec. composition

  17. Analysis Time • Given: • Bag rocks Identify the rocks

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