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Comment: 15:42 - 16:24 (00:42)
Source: Annenberg/CPB Resources - Earth Revealed - 18. Metamorphic Rocks
Keywords: "James Sadd", metamorphism, experiment, composition, temperature, pressure, mineral, "metamorphic rock", atom, geologist
Our transcription: Metamorphism has been compared to cooking.
The dish that you wind up with depends both on your starting ingredients and on the way you cook them.
Likewise laboratory experiments have shown that the composition of rocks changes very little during metamorphism.
But as temperature and pressure increase, the atoms within the rock become mobile and recombine to form new minerals.
These experiments have also shown that the various metamorphic minerals or assemblages of minerals found together, form only within specific ranges of temperature and pressure.
So geologists can use minerals and metamorphic rocks as pressure gauges and thermometers to understand the conditions under which metamorphism took place.
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