How Metamorphic Rock Is Formed
Metamorphic rocks are formed when other rocks are changed by heat and pressure deep inside the earth. Sometimes new mineral crystals form as the rock changes. Sometimes existing minerals are softened and reshaped.
How do you know if a rock is metamorphic? Metamorphic rocks are very hard. Pressure and heat gradually changed the original rock into much harder metamorphic rock. For example, a hard and brittle metamorphic rock called slate formed from a softer sedimentary rock made from clay called shale.
Some metamorphic rocks have stripes or bands. Gneiss is an example of this kind of metamorphic rock.
Some metamorphic rocks contain pebbles that were flattened and stretched by pressure deep inside the earth. Schist is an example of this kind of metamorphic rock.
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schist