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Rocks

Rocks. With few exceptions, rocks are composed of minerals. Most rocks are mixtures of minerals, which may be present in any proportion. Three classes of Rocks. Sedimentary Metamorphic Igneous. We classify Rocks by how they were Formed. Igneous Rocks.

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Rocks

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  1. Rocks • With few exceptions, rocks are composed of minerals. • Most rocks are mixtures of minerals, which may be present in any proportion.

  2. Three classes of Rocks • Sedimentary • Metamorphic • Igneous

  3. We classify Rocks by how they were Formed.

  4. Igneous Rocks • Form from the cooling and solidification of molten (liquid) rock. • The type of igneous rock is determined by how quickly it cools.

  5. Igneous Rocks • Intrusive rocks – result from slow cooling and high pressure deep within the Earth. • Usually contain intergrown crystals.

  6. Igneous Rocks • Extrusive rocks – result from the rapid cooling of molten rock at or near the surface. • Usually has a total lack of crystal growth. May be glassy or Vesicular.

  7. Igneous Rocks

  8. Igneous Rocks

  9. Igneous Rocks

  10. Igneous Rocks

  11. Sedimentary Rocks • Earth is covered in a veneer (thin) layer of sedimentary rocks. This makes them easy to find. • Sediments are produced by the breakdown of rocks at the Earth’s surface. • When sediments are compacted and cemented sedimentary rocks are formed.

  12. Sedimentary Rocks • Sedimentary rocks often have separate and distinct parallel layers (strata). • We break sedimentary rocks into two classes. 1- Clastic and 2 – Non Clastic

  13. Sedimentary Rocks • Clastic sedimentary rocks are formed from rock particles

  14. Sedimentary Rocks • The particles may be very small as in sandstone or microscopic as in shale.

  15. Sedimentary Rocks • Non Clastic rocks are usually chemical precipitates like limestone.

  16. Sedimentary Rocks • Sedimentary rocks can often contain fossils

  17. Metamorphic Rocks • Formed when rocks are exposed to great heat and pressure deep inside the Earth. • The changes are made while the rocks remain solid.

  18. Metamorphic Rocks • Crystals may be distorted or forced into bands called Foliation.

  19. Metamorphic Rocks • Sometimes there is evidence of recrystalization. Ex. Shale => Schist

  20. Metamorphic Rocks • Or Limestone => Marble

  21. Metamorphic Rocks • Or Sandstone => Quartzite

  22. As the Earth formed from cooling molten rock the “parent” rocks were Igneous. • After these rocks were exposed to the dynamic forces of the Earth the other classes of rocks were formed.

  23. Rock Cycle

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