GEOL 1303 Lecture Notes - Lecture 9: Volcanic Plateau, Subduction, Extrusive Rock
4 Mar 2016
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Intrusive/extrusive depends on where the nal resting place of rock is, where it cools etc. Volcanic bombs (rocks) smooth, break when hit ground. Classi ed based on: depth of emplacement (shallow or deep) areal extent of surface outcrop (how much you see on surface) Controlled by rate at which the rock cools also by magma chemistry (high/low viscosity) Growth of grains must obtain x amount of atoms from the melt depends on cooling rate, viscosity. Extrusive surface enviro - cold thin fast cooling. Vesicles - bubbles/air pockets in rocks (think pumice) Center is harder and less eroded rock, so left with a neck. Cuts through other rock (across layers, perpendicular even) Can be small or large (wide, less wide etc) Dike comes up laterally between layers (not cutting, with the grain/in line with) Looks like ordinary lava ow, but not bc chilled margins. Mushroom of lava ow creates bulge on surface.
