GEOL 103 Lecture 3: Plate Boundaries
3 Sep 2019
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Through convection, hot magma rises (basaltic crust, low silica) through cracks and fissures where plates are pulling apart. Hot magma rises, comes to the surface as lava, cools and makes new crust. Two plates pulling apart at a divergent boundary. Divergent boundaries exposed on the surface and areas of rifting result in shield volcanoes that are flat and wide. Continent is being stretched and pulled apart. Might get a little fissure volcanism if magma comes up. Crust does thin out but does not create volcanoes. Rift valleys form and lava can come up through the cracks where the crust thins. Rock slides down into blocks (plateaus) and creates leveled rift valleys. Hanging wall - hangs over your head. If footwall moves up relative to hanging wall, it is called a normal fault. Hanging wall moves down relative to the footwall. Creates rock folds (where mountains form) and suture zones (where one plate goes under the other)
