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Rocks.

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Presentation on theme: "Rocks."— Presentation transcript:

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: Laccolith: ____________ 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 ___________

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16 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)

17 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)

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19 Extrusions Volcanic neck: Lava flow: Lava capped-plateau
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

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