For an explanation, see the main splats page
SPLATS about metamorphic rocks
The principles of metamorphic rocks
See also About igneous rocks
- Metamorphic rocks are formed by the action of heat and pressure on pre-existing rocks, mainly sedimentary rocks, which are changed by that action.
- Local or contact metamorphism, extending over a few metres or tens of metres, can be caused near the Earth's surface by a flow or sill. It happens quickly.
- Large-scale regional metamorphism happens only at great depths, and may extend over very large distances: it involves heat, pressure, and a long time scale.
- When sedimentary rocks are heated and compressed for long periods, limestone changes to marble, sandstone changes to quartzite and shale changes to slate.
- In some cases, fossils formed in a sedimentary rock may still be recognizable after the rock has undergone metamorphism, confirming its sedimentary origins.
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