EOSC 114 Lecture Notes - Lecture 10: Magma Chamber, Stratovolcano, Mafic
30 Jan 2018
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Where do volcanoes occur: plate boundaries, hot spots. No volcanoes at transform boundaries and we only get volcanoes at the subduction kind of convergent boundaries. Not e(cid:454)posed at the earth"s surfa(cid:272)e, e(cid:454)(cid:272)ept i(cid:374) o(cid:374)e lo(cid:272)atio(cid:374), i(cid:272)ela(cid:374)d, (cid:271)e(cid:272)ause of the prese(cid:374)(cid:272)e of a hotspot. Oceanic volcanic arcs key difference: oceanic crust is the overriding plate does(cid:374)"t i(cid:374)tera(cid:272)t with continental crust, less felsic magma. Why are arc volcanoes typically explosive: they erupt gas-rich magmas. The gasses come from their pathway to the surface minerals with gasses increases gas content as it goes through the continental crust. Mafic magma from a plume of hot mantle. Hot spot under a continent = thicker to melt, more silica etc. , silica rich: ex. Mantle material rises in a dike, pressure decrease. Mantle material rises in cylindrical plume, pressure decrease. Why is basalt the most common rock type in hawaii: because the hotspot is located beneath ocean crust, which melts to produce magic magma.
