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Rocks

Rocks. What’s a Rock?. A solid chunk of one or more minerals (or sometimes mineral-like matter). The Rock Cycle. A Quick Quiz. The type of rock that starts it all! IGNEOUS! A rock formed by squeezing and heating. METAMORPHIC

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Rocks

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  1. Rocks

  2. What’s a Rock? • A solid chunk of one or more minerals (or sometimes mineral-like matter)

  3. The Rock Cycle

  4. A Quick Quiz • The type of rock that starts it all! IGNEOUS! • A rock formed by squeezing and heating. METAMORPHIC • A rock formed from smaller rocks and material being compacted together. SEDIMENTARY

  5. More Questions! • A rock formed from cooling magma or lava IGNEOUS • A sedimentary rock might have originally been one of this(these) kind of rock(s) IGNEOUS, METAMORPHIC, or SEDIMENTARY • A metamorphic rock might have originally been one of this(these) kind of rock(s) IGNEOUS or SEDIMENTARY

  6. Rocks, Part 2 Igneous Rocks

  7. Igneous • From Latin ignis = FIRE! • Formed when lava or magma cools and hardens

  8. Examples of Igneous Rocks Obsidian Rhyolite Granite Pumice Basalt

  9. Several Ways to Classify Igneous Rocks • Intrusive vs. Extrusive • Texture • Composition

  10. 2. Texture • Coarse Grain Texture • Fine Grain Texture • Glassy Texture

  11. Coarse Grain Texture • Relatively Large Crystals • Formed by slow cooling of magma in Earth Granite

  12. Fine Grain texture • Smaller Crystals • Formed by rapid cooling of magma or lava Rhyolite

  13. Glassy Texture • Crystals so tiny the rock looks like glass • Formed by extremely fast cooling of lava Obsidian

  14. 3. Composition • Granitic Composition • Basaltic Composition

  15. Granitic Composition • Lots of light-colored silicates, esp. quartz and feldspar • Usually speckled with about 10% dark silicates • Make up most of continental crust Granite Rhyolite

  16. Basaltic Composition • Mainly dark silicates • Darker and denser than granite • Make up most of ocean floor (formed at ocean ridges) Basalt Gabbro

  17. Rocks, Part 3 Sedimentary Rocks

  18. Sedimentary From Latin sedimentum = settling Formed when sediments are compacted and cemented together

  19. Create a Sedimentary Rock in Only 3 Steps! Step 1: Weather/erode parent rock and deposit sediment. Step 2: Compact sediment. Step 3: Cement sediment. Voila! Your sedimentary rock is complete.

  20. Step 1: Weather/erode parent rock and deposit sediment. Table Mountain, South Africa

  21. Step 2: Compact sediment. As sediments are buried, the increasing weight of sediments above them squishes them together and removes most water.

  22. Step 3: Cementation. Finally, dissolved minerals are deposited in the spaces between the sediments. The minerals solidify and cement the particles together (like mortar).

  23. Examples of Sedimentary Rocks Rounded, Gravel-sized Sediment Conglomerate

  24. Another Example Angular Gravel-sized Sediment Breccia

  25. And Another Sand-sized Sediment Grains Sandstone

  26. Sandstone in Architecture The Treasury Petra, Jordan And It’s Still Used Today!

  27. And Another Example Fine-grained Sediment Shale

  28. More Sedimentary Rocks Siltstone Chalk Limestone

  29. A Special Word About Limestone Very common Main mineral: Calcite (CaCO3) Often used as building material Often formed from marine organisms

  30. Indiana Limestone in Buildings AND 35 of 50 Statehouses made of Indiana Limestone! National Holocaust Museum

  31. Why Studying Sedimentary Rocks is Useful Formed by adding successive layers Contents of layers tell a story of that time: Fossils of organisms, floods, volcanoes, earthquakes, & climate Limestone from Indiana??? A Trilobite Fossil

  32. Rocks, Part 4 Metamorphic Rocks

  33. Metamorphic “To change form” due to heat and pressure Formed from either igneous or sedimentary rocks

  34. The Role of Heat Provides energy to drive reactions between minerals Existing minerals may be re-crystallized into a different form or new minerals may be formed Source of heat: Contact with magma itself Increasing depth (temperature increases 20-30oC per kilometer)

  35. Role of Pressure Farther down a rock is buried, the greater the pressure Increased pressure smooshes minerals together or causes them to re-crystallize Under high temp and pressure, rocks “flow” instead of fracturing

  36. Foliated vs. Nonfoliated Metamorphic Rocks Foliated = “striped” • Nonfoliated = “not striped” Gneiss Marble

  37. More Metamorphic Rocks Shale Slate

  38. Another Meta Granite Gneiss

  39. And Another Limestone Marble

  40. One More Sandstone Quartzite

  41. And Lastly… Hornfels No specific composition Was “baked” by magma in contact the parent rock

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