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Metamorphic Rocks. Heat and Pressure. Metamorphic Rocks are created out of old rocks by HEAT and PRESSURE. But, they don’t melt (if they did, they would be igneous). All Metamorphic Rock starts off as Igneous or Sedimentary Rock.
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Metamorphic Rocks Heat and Pressure
Metamorphic Rocks are created out of old rocks by HEAT and PRESSURE But, they don’t melt (if they did, they would be igneous).
All Metamorphic Rock starts off as Igneous or Sedimentary Rock • Geologists are always interested in what kind of rock a metamorphic rock used to be. However, if extreme deformation has occurred, this can be quite difficult.
Heat and Pressure • As you go deeper into the earth, it becomes HOTTER and HOTTER • As you go deeper into the earth, there is more and more PRESSURE because there is more rock above you.
Heat and Pressure • Heat makes rock more MALLEABLE (more bendy) • Pressure DEFORMS rock by compacting it, stretching it, or twisting it. • Together HEAT and PRESSURE change the composition of the old rock • Remember: Metamorphic rock never melted (or else it would be igneous)
Foliation • Foliation occurs when a rock is squeezed and shortened by extreme pressure to form bands and layers • However, foliation does not always happen. There are both foliated and non-foliated metamorphic rocks
Let’s see it in action… http://www.classzone.com/books/earth_science/terc/content/visualizations/es0607/es0607page01.cfm?chapter_no=visualization
Two types of Metamorphism Regional • When metamorphism happens to an extensive (big) REGION of rock • This can happen when two masses of rock collide, or when rock is pushed deep underground
Two types of Metamorphism Contact • Contact Metamorphism happens when rock comes in CONTACT with hot magma (but does not melt itself). • This can happen at the surface or underground and only happens to a small amount of rock
Where are metamorphic rocks found? • Metamorphic rocks can be created out of any type of rock and are thus very hard to classify. • However, because metamorphosis is caused by extreme HEAT and PRESSURE, metamorphic rocks are usually found where something extreme has happened (like volcanic activity or two plates colliding)
Some examples… Before: Granite After: Gneiss
Some examples… Before: Shale After: Slate
Some examples… Before: Limestone After: Marble
Metamorphic Rock… • Is created out of old rock by heat and pressure • Doesn’t melt (or else it would be igneous rock) • Is often foliated/deformed by extreme pressure • Formed by regional or contact metamorphism