GLGY 209 Chapter Notes - Chapter 4: Amphibole, Andesite, Xenolith
7 Apr 2016
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Igneous acivity occurs in four seings: isolated mantle plume hot spots, volcanic arcs bordering deep ocean trenches, mid-ocean ridges, and coninental rits. Most igneous acivity takes place at mid ocean ridges. Riting at the mid ocean ridge leads to decompression meling ( decompression meling is where rock stays solid because it"s under so much pressure from overlying rock. ) Subaerial volcanoes usually reside in arcs that mark convergent tectonic plate boundaries. Mantle plume hotspots generate igneous acivity independent of tectonic plate boundaries. (basically means that, volcanoes show up out of nowhere) Hotspots erupt at oceanic crust and coninental crust. Usually rock is maic at oc and a mix of maic and felsic @cc. The base of the earth crust is hot enough to melt rock. But b/c of heavy pressure, it doesn"t melt. As rock moves to shallower depths, it begins to melt. When volailes are introduced to the hot mantle.
