Heat and pressure

Metamorphism is the part of the rock cycle where rocks change into different rocks when subjected to heat and pressure, which can come from a variety of sources. Examples might include a granite intruding into other rocks, heating them and altering them as element charged fluids are spat out during the slow cooling process (called contact metamorphism, usually resulting in aureoles of different sets of characteristic minerals around the intruding pluton), or the huge pressures generated during continental collision, when large slabs of rocks called nappes detach from the lower crust and pile up in slow motion like a pushed tablecloth. The rocks at the bottom of the heap (now called a mountain chain) are baked and crushed until the minerals start to change.

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