EARTH121 Study Guide - Final Guide: Moraine, Love Wave, Cryosphere
19 Jan 2015
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Document Summary
Transformation results from exposure of pre-existing solid rock to heat, pressure and fluid chemical activity to change the mineral composition and texture. Chemical composition reflects parent rock but texture and mineral makeup depends on metamorphic processes involved. Controlling factors in metamorphism: composition of the parent rock, heat increases the rate of chemical rxns (most powerful agent) Upper crust is 20-30c/km, 12k reaches 245c, water doesn"t boil because of the increase pressure. Confining pressure/uniform stress = squeezing of the rock from all directions, increases with depth. Directed pressure/differential stress = minerals align in the direction of least stress. Tensional stress = pulling apart motion, crustal stretching. Shear stress = forces parallel but in opposite direction. Foliation: platy minerals become more aligned parallel to direction of least stress under pressure. An increase in metamorphic grade is indicated by minerals that are stable at progressively higher temperatures and pressures.
