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Rocks PowerPoint Presentation

Rocks

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Rocks

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  1. Rocks

  2. Igneous Rocks • Intrusive: form when magma cools ___________ inside the Earth. • Extrusive: form when lava cools ___________ on the Earth’s surface.

  3. Texture of Igneous rocks • Intrusive igneous rocks: • Cool slowly • Allows time for the minerals to form _________ crystals • Rocks with large crystals have a _____________ texture • Example: granite, gabbro

  4. Granite Gabbro

  5. Extrusive igneous rocks • Cool _____________ • Quick cooling doesn’t allow time for large crystals to form • This produces a ___________ texture • Example: basalt • Extremely rapid cooling cause NO crystals to form • Example: obsidian (volcanic glass) • Sometimes gasses are trapped in cooling magma and form bubbles • Example: pumice ,scoria

  6. Basalt Obsidian

  7. Pumice Scoria

  8. Igneous Rock Structures • Intrusion: underground rock mass made of intrusive rock • Extrusion: surface rock mass of extrusive rock

  9. Intrusions • Batholith: • ____________ intrusion • Large underground mass of rock which may cover hundreds of miles • Laccolith: • Magma flows between rock layers and spreads upward, pushing the rock above into an ___________

  10. Sill: • Sheet of magma ________________rock layers and hardens • They are always parallel to the ______________ rock layers • Can be thin (few centimeters) or thick (several hundred meters)

  11. Dike: • Forms when magma forces its way into existing fractures • Once magma hardens it is called a dike • Dikes cut ___________ rock layers (perpendicular to them)

  12. Extrusions • Volcanic neck: • Solidified central shaft of a volcano • Lava flow: • Erratically shaped mass of extrusive rock • Lava capped-plateau • Lava that spreads over vast area and hardens