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How Rocks Form

- Classifying Rocks. How Rocks Form. Geologists classify rocks into three major groups: igneous rock, sedimentary rock, and metamorphic rock. - Igneous Rocks. Classifying Igneous Rocks. Igneous rocks are classified according to their origin, texture, and mineral composition. - Igneous Rocks.

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How Rocks Form

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  1. - Classifying Rocks How Rocks Form • Geologists classify rocks into three major groups: igneous rock, sedimentary rock, and metamorphic rock.

  2. - Igneous Rocks Classifying Igneous Rocks • Igneous rocks are classified according to their origin, texture, and mineral composition.

  3. - Igneous Rocks Mineral Mixture • Granite is a mixture of light-colored minerals, such as feldspar and quartz, and dark-colored minerals, including hornblende and different types of mica. But granite can vary in mineral composition. This affects its color and texture. • Study the circle graph and then answer the questions.

  4. Feldspar Reading Graphs: What mineral is most abundant in granite? - Igneous Rocks Mineral Mixture

  5. 10% Reading Graphs: About what percentage of granite is made up of dark minerals? - Igneous Rocks Mineral Mixture

  6. 100% - (35% + 10%) = 55% Calculating: If the amount of quartz increases to 35 percent and the amount of dark-colored minerals stays the same, what percentage of the granite will be made up of feldspar? - Igneous Rocks Mineral Mixture

  7. The overall color would be darker. Predicting: How would the color of the granite change if it contained less feldspar and more mica and hornblende? - Igneous Rocks Mineral Mixture

  8. - Igneous Rocks Main Idea Igneous rocks are classified by origin, texture, and composition. Detail Detail Detail Extrusive rock forms from lava on the surface; intrusive rock forms from magma from beneath the surface. Intrusive rocks have larger crystals than extrusive rocks because they cool more slowly. High-silica rocks are light colored; low-silica rocks are dark colored.

  9. End of Section:Igneous Rocks

  10. - Sedimentary Rocks From Sediment to Rock • Most sedimentary rocks are formed through a series of processes: erosion, deposition, compaction, and cementation.

  11. - Sedimentary Rocks Sedimentary Rocks • From Sediment to Rock • Erosion • Deposition • Compaction • Cementation • Uses of Sedimentary Rocks • Building Materials • Tools

  12. End of Section:Sedimentary Rocks

  13. - Metamorphic Rocks Do you know…….. Q. Why do the crystals in gneiss line up in bands? A. Gneiss is a type of metamorphic rock that is foliated—the crystals are flattened to form parallel lines. Q. How does quartzite form from sandstone? A. High temperature and pressure on the minerals in sandstone cause them to be changed into minerals that make up quartzite.

  14. End of Section:Metamorphic Rocks

  15. - The Rock Cycle A Cycle of Many Pathways • Forces deep inside Earth and at the surface produce a slow cycle that builds, destroys, and changes the rocks in the crust.

  16. Graphic Organizer Metamorphic Igneous Organic Foliated Extrusive Chemical

  17. - The Rock Cycle Exit Quiz: Sequencing • Before you leave, and without using your notes from today, draw the rock cycle, using the three types of rock below with arrows. Metamorphic Igneous Sedimentary

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