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Grade 7 Science Unit 4: The Earth’s Crust

Grade 7 Science Unit 4: The Earth’s Crust. Classification of Rocks. Questions to Ponder…. How do the crystals or minerals form in a rock? Why do some rocks have layers? Why do some rocks have rounded particles while others have angular particles?. Rocks.

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Grade 7 Science Unit 4: The Earth’s Crust

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  1. Grade 7 ScienceUnit 4: The Earth’s Crust Classification of Rocks

  2. Questions to Ponder… • How do the crystals or minerals form in a rock? • Why do some rocks have layers? • Why do some rocks have rounded particles while others have angular particles?

  3. Rocks • Are combinations of two or more minerals. • They can be grouped into three families depending on how they are formed.

  4. 1. Igneous Rocks • Result from the cooling of molten (melted) rock material. • The cooling creates crystals in the rocks. • Basalt and granite are the most common.

  5. Molten Rock can form… Above the ground Below the ground Lava Magma

  6. 2 types of Igneous Rock Intrusive • formed below the surface of the Earth. • Rocks cool very slowly. • They have large crystals.

  7. Gabbro Granite

  8. Extrusive • Formed above the Earth’s surface. • Rocks cools quickly. • They have small crystals.

  9. Basalt Rhyolite Obsidian

  10. 2. Sedimentary Rocks • Form from the compaction and cementation (lithification) of sediments into visible layers called beds.

  11. Sedimentary rocks are classified by grain size… • Small particles (silt or mud) Shale

  12. Medium Particles (sand – can roll between your fingers) Sandstone

  13. Large Particles (gravel) Conglomerate

  14. Plant and animal particles Limestone

  15. 3. Metamorphic Rocks • Result when pre-existing rocks (parent rocks) undergo changes due to heat, pressure and water. • This is a long and slow process.

  16. Parent Rocks… • Sedimentary • Metamorphic PARENT: Shale Slate

  17. Sedimentary • Metamorphic PARENT: Limestone Marble

  18. Sedimentary • Metamorphic PARENT: Sandstone Quartzite

  19. Igneous • Metamorphic PARENT: Granite Gneiss

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