EPSC 201 Lecture Notes - Lecture 13: Asthenosphere, Pumice, Continental Crust
20 Jul 2016
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Classification: crystalline classification o based on composition and texture, glassy classification o more common in felsic igneous rocks. Isolated hot spots o continental rifts o mid ocean ridges: established or newly formed tectonic plate boundaries, except: hot spots, which are independent of plates. Volcanic arcs: most sub aerial volcanoes on earth reside in arcs, mark convergent tectonic plate boundaries o deep oceanic trenches and accretionary prisms o subducting oceanic lithosphere adds volatiles (water) o rocks of the asthenosphere partially melt o magma rises and creates volcanoes on overriding plate o magma may differentiate, examples o aleutian islands o japan o java and sumatra. Independent tectonic plate boundaries: about 50 100 mantle plume hot spot volcanoes exist, may erupt through oceanic or continental crust o oceanic mostly mafic magma (basalt) o continental mafic and felsic (basalt and rhyolite, burn a volcano chain through overriding tectonic plate o creates a hot spot track.
