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Rocks

Rocks. What is a rock?. Which of the following are rocks: Ice Water Coal Dead Plant Table Salt Processed Sugar Mined Diamond Artificial Diamond. Definition. Solid Naturally occurring Combinations (mixtures!) Minerals and/or organic materials. List. Rocks Not Rocks Ice Water

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Rocks

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  1. Rocks

  2. What is a rock? • Which of the following are rocks: Ice Water Coal Dead Plant Table Salt Processed Sugar Mined Diamond Artificial Diamond

  3. Definition • Solid • Naturally occurring • Combinations (mixtures!) • Minerals and/or organic materials

  4. List RocksNot Rocks Ice Water Coal Dead Plant Salt Sugar Mined diamonds Artificial Diamonds

  5. How are igneous rocks formed? • Are made from magma that has been cooled down from liquid to solid

  6. Difference between magma and lava?

  7. Answer • Magma is molten rock inside the Earth • Lava is molten rock on the surface of the Earth

  8. Rock Characteristics • Use to tell history, origin of the rock • Did it form inside or on the surface of Earth • How long did it take to form?

  9. Rock Characteristics Rock Texture: Relates to size of the mineral crystals. The size of the crystal indicates the amount of time it takes to cool down and form a solid object. The larger the crystals, the longer the time of formation Types of textures- Coarse Grained: Large crystals Fine Grained : Small crystals. Will usually not be able to see crystals without microscope

  10. Other texture types • Glassy: No crystals, even under a microscope • Indicates very rapid cooling of lava (seconds) • Vesicular: Rocks with holes • Holes indicate escape of gases during rapid cooling

  11. Color (2nd Characteristic) • Color indicates composition of the rock • Light colored rocks: indicate rocks with high concentrations of Si, O, K and Na • White, pinks and gray • These rocks have a Felsic composition • Formed within continents

  12. Color • Dark colored: Color dominated by dark greens and black • These rocks have high concentrations or Fe, Mg and Ca • These rocks have a mafic composition • These rocks are formed within oceans

  13. Nothing is black or white… • A lot of rocks are combinations of felsic and mafic materials • Color will be medium dark (usually dark gray) • These have an intermediate composition

  14. Felsic Rocks

  15. Mafic Rocks

  16. Density (3rd Characteristic) • Mafic rocks are generally more dense than Felsic rocks

  17. Rock Names • Match the name to your rock sample based on your observations • Basalt- fine grained , mafic • Gabbro- coarse grained, mafic • Granite- coarse grained, felsic • Obsidian- glassy, mafic • Pumice- vesicular (very small holes), felsic • Tuff- fine grained, felsic • Scoria – vesicular (larger holes), mafic

  18. Types of volcanic rocks • Obsidian: Mafic, Glass, no crystals, instant solid • Tuff, pumice: Felsic, Tiny crystals, with holes, quick solidification • Basalt: Mafic, tiny crystals, lava solidification • Granite, Felsic, large crystals, magma solidification without exposure to air

  19. What do the rocks tell about its history… • Basalt, obsidian, pumice, tuff and scoria are examples of extrusive igneous rocks. • These rocks were created from the material extruded from an volcanic eruption • In general, extrusive rocks have no crystals or very small crystals: short cooling time

  20. Gabbro,and granite are examples of intrusive igneous rocks • Formed when magma slowing cools inside the earth before exposed through erosion • Formed when magma is given a chance to slowly cool over millions of years, without being exposed to the surface of the earth

  21. Why do intrusive rocks grow such big crystals? • Because the rocks in the interior of the Earth are poor conductors of heat, it takes a long time for the hot magma to be cooled. Thus, the intrusive igneous rocks have a coarse-grained texture due to their slow cooling.

  22. Devils tower

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