EPSC 201 Lecture Notes - Lecture 19: Craton, Stata, Isostasy
26 Jan 2017
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Document Summary
Develops as a result of the shear between the subducting and overriding plates: shock metamorphism. When earth is struck by a comet or asteroid, the impact generates extremely high pressure and heat. These conditions vaporize rock and/or generate high-pressure minerals. Index minerals can be used to identify the metamorphic grade of a rock. The regions between two isograds define metamorphic zones , typically named after an index mineral that was not present in the previous, lower grade zone: large regions of ancient high-grade metamorphic rocks are exposed in continental interiors. Called shields, these are the eroded remnants of orogenic belts. Shield rocks form the basement under sedimentary cover over much of the world. Around a mountain range if you apply shear stress or compression, on a large scale we get folding. When sedimentary rocks are buried deep within the crust, where confining pressures are great, strata can be deformed into very tight folds stacked one atop of each other.
