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Rocks

Rocks. Igneous, Metamorphic, Sedimentary. What is a Rock?. A rock is a mixture of minerals , mineraloids, glass and organic matter. Common minerals found in rocks include: feldspar, hornblende, and mica . Granite is a mixture of these minerals. Rock Cycle.

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Rocks

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  1. Rocks Igneous, Metamorphic, Sedimentary

  2. What is a Rock? • A rock is a mixture of minerals , mineraloids, glass and organic matter. • Common minerals found in rocks include: feldspar, hornblende, and mica. • Granite is a mixture of these minerals.

  3. Rock Cycle • There are three types of rock: • Igneous – formed by melting and cooling magma and lava. • Sedimentary – formed by weathering and erosion • Metamorphic – formed by heat and pressure over time. • Rocks change over time.

  4. Igneous Rocks • Molten or liquid material from a volcano or from deep inside the Earth, cools to form igneous rocks. • Magma – High temperatures and high pressure deep in the Earth cause rocks to melt and form hot magma.

  5. Earth’s Interior

  6. Earth’s Interior: Temperatures

  7. Igneous Rocks • At 60 to 200 km below the Earth’s surface the temperatures reach 1400oC. (2550oF) • Magma rises because it is less dense than the surrounding solid rock.

  8. Igneous Rocks • Lava is magma that reaches the surface. Ropeypahoe lava

  9. Igneous Rock: Intrusive Rocks • These are igneous rocks that form below the Earth’s surface. • They have large mineral grains. • Examples : Gabbro • Diorite

  10. Igneous Rocks:Extrusive • These rocks are formed quickly when lava cools on or near the Earth’s surface. • Air and Moisture causes lava to cool quickly. • The quick cooling does not allow large crystals to form. • Extrusive rocks have a fine-grained structure.

  11. Igneous Rocks: Extrusive Examples • Rhyolite • Obsidian

  12. Igneous Rocks: Extrusive • Scoria - formed from gassy lava, it has air-pockets that give it a spongy appearance. • Pumice: Lava “foam”, some samples float in water.

  13. Volcanoes • Pompeii, Italy Web

  14. Igneous Rocks: Vocabulary • Mafic – composed of ferromagnesian minerals- olivine, pyroxene, and amphibole. These are oceanic. The water cooled them quickly. • Felsic – composed of mostly quartz and feldspar. These are continental, cooling on dry land.

  15. Igneous Rock • Aphamitic – texture , made of crystals too small to be seen without a microscope. • Porphyritic – rocks with two cooling rates, They have a mix of large and small crystals. • Porphyritic = look like chocolate chips! cookies

  16. Igneous Rocks: Vocabulary • Vesicular – gassy when formed, the rocks look like sponges.

  17. Igneous RocksTexture – Cooling Rate – Crystal Size – Description - Type • Vesicular -fast- none - air bubbles – extrusive • Glassy – fast – none - very smooth – extrusive • Aphanitic –quick–microscopic –fine grained - extrusive • Granitic – slow – visible – coarse grained - intrusive • Porphoritic – slow/then quick – small&large – Chocolate chip - Intrusive

  18. Mineral Composition of Igneous RocksName – Minerals – Color – Density- Crustal Formation • Felsic – K-Feldspar, muscovite, quartz – Light – Low density – Continental • Intermediate- Hornblende, biotite, Na-plagioclase – Medium – Medium density – Continental/Ocean • Mafic – Olivine, Augite, Ca-plagioclase – Dark – High density - Oceanic

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