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Geog revision
Question | Answer |
---|---|
Igneous rocks | Rocks formed from lava cooling |
Examples of igneous rocks | Granite and Basalt |
How is granite formed | It is an intrusive rock, meaning it forms deep under the surface of the earth Magma cools slowly under the crust This allows large crystals to form |
Info about granite | It is course-grained Contains large crystals, such as mica, feldspar and quartz Usually grey in colour Resistant to erosion Used for monuments and gravestones Course grained |
Where can granite be found | In the Leinster Batholith. A batholith occurs when magma cools slowly deep below the crust, and over millions of years the surrounding rock is weathered away quicker than the granite. This results in a dome shaped rock protruding from the ground. |
Origin of leinster batholith | The Leinster Batholith owes its origin to the volcanic activity that happened during Caledonian folding 400 million years ago. |
How is basalt formed | It is an extrusive rock, which means that lava cooled quickly on or near the surface of the crust. Basalt has either small or no crystals because they didnât have time to form. |
Info about basalt | It is black in colour It is very hard, so it is used for surfacing roads It is fine grained It sometimes forms in hexagonal columns because of rapid cooling, like at the Giantâs Causeway, Co. Antrim |
Where can basalt be found | The Giantâs Causeway, Co. Antrim The Antrim-Derry Plateau |
Sedimentary rocks | Limestone and sandstone |