Earth Sciences 2240F/G Lecture Notes - Lecture 9: Mid-Ocean Ridge, Nuclear Winter, Viscosity
20 Apr 2016
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For the purpose of this chapter, we can forget about eruptions of basaltic magma from regular spreading centers not catastrophic enough for us! Explosive eruptions from volcanoes in subduction zones, and. The almost unbelievably catastrophic eruptions from giant resurgent calderas (which normally form over the tops of mantle plumes that pierce continents). In chapter 7 we noted that any magma produced in the asthenosphere will always be less dense than the rock from which it was produced so it will rise towards the surface. Any magma will erupt when it gets so close to surface that the overlying pressure of the load of rock over it is less than the volatile pressure within it. However, that eruption will be explosive only if: The magma is highly viscous (high amount of si) The magma has a high content of exsolved volatiles (like h2o and co2)
