sci245_r6_History_of_Rock_Worksheet - History of Rock...

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History of Rock Worksheet SCI/245 Version 6 1 Associate Level Material History of Rock Worksheet Write a 500- to 750-word explanation regarding the role of plate tectonics in the origin of igneous rocks. Igneous rocks form in three main places: where lithospheric plates pull apart at mid-ocean ridges, where plates come together at seduction zones and where continental crust is pushed together, making it thicker and allowing it to heat to melting. There are two ideas about igneous rocks that are geologically important. The first idea is that igneous rocks evolve - they change from one kind of rock into another. The second idea is that rocks are not randomly distributed across the earth. Specific kinds of rocks are always found in specific places for specific reasons, all tied into plate tectonic processes. The word “igneous” comes from the Latin word for fire because the Igneous rocks begin as hot, fluid material. The hot, fluid material could have been erupted from the Earth's surface which is called magma, before the erosion. Most people mistakenly think of lave and magma as a liquid, like molten metal but scientists find that magma is usually more of a mushy kind of liquid that carries a load of mineral crystals. Magma turns into crystallized minerals and some crystallize sooner than others. When they crystallize, they leave a liquid behind that changes chemical composition. When a body of magma cools, it evolves and moves through the crust that interacts with other rocks and evolves further. You can tell the three different types of igneous rocks apart by their texture and the size of the mineral grains. The extusive rocks cool
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This note was uploaded on 03/07/2012 for the course SCI 245 taught by Professor N/a during the Spring '09 term at University of Phoenix.

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sci245_r6_History_of_Rock_Worksheet - History of Rock...

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