GG231 Lecture Notes - Lecture 5: Mount Unzen, Mid-Ocean Ridge, Silicate Minerals
Document Summary
Volcanic activity is directly related to plat tectonics. Most active volcanoes are located near plate boundaries. Mid ocean ridges and subduction zones are sites where magma reaches the surface and erupts as lava. Lithospheric plates do not move around on an ocean of molten rock. Most magmas come from the asthenosphere, where rick is close to its melting temperature. There are 3 main ways which silicate rocks can melt. Decompression melting occurs when the pressure exerted on hot rock within the asthenosphere is reduce. The melting temp for mantle silicate rocks at earth"s surface is approximately 1200 degrees celsius. Addition of volatiles lowers the melting temperature of rocks by helping to break chemical bonds within silicate minerals. Rocks that are close to their melting temp will melt in the presence of added volatiles. Volatiles are chemical compounds that exist in gaseous state at.
