ERTH 2415 Chapter Notes - Chapter 5-6: Subduction, Rhyolite, Volcanic Gas
3 Dec 2015
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Document Summary
Oceanic (spreading center) volcanoes are relatively peaceful whereas subduction zone volcanoes are explosive and dangerous: different because of differences in magma. 3 types of magma: basalt, andesite, and rhyolite: based on their silicon and oxygen (sio2) percentage. Plutonic rocks when magma solidifies and cools below the surface. Water concentration in magma plays a controlling roll. Viscosity of magma determines if it will produce a peaceful or explosive style. Volatiles dissolved gases held in magma. Water is most abundant dissolved gas in magma. Water lowers melting point of rock causing it to liquefy and start to move to of eruption the surface. General rule, if a volcano has a well-formed and aesthetic conical shape, it is. Basaltic magma mainly composed of dark minerals that crystallize first in a cooling magma. Have highest temperatures and lowest sio2 contents: produced by partial melting of the mantle. Rhyolitic magma mainly composed of light colour minerals that crystallize last.
