ENVIR ST 106 Chapter Notes - Chapter 5: Long Valley Caldera, Andesite, Cascade Range
30 Oct 2014
School
Department
Course
Professor
Document Summary
A place where magma comes out as lava. Magma: molten material below the surface of the earth. Lava: molten material above the surface of the earth. Sources of magmas: plate boundaries: at divergent-typically melted aesthenosphere- and convergent- the composition of the subducted plate determines the composition of the lave- plate boundaries hot spots: don"t need plate boundaries. As the plate moves, the volcanoes over the hot spot become dormant and new volcanoes form. Hot spots in ocean basin produce basalt lava. Hot spots under continental crust produce a felsic and often explosive lava. Partial melting of asthenosphere: pressure, temp, effects: aside from an increase of temperature, two things can trigger melting. This promotes melting at a spreading ridge or rift zone: pressure from the overlying plates is reduced as they split and part and astenosphere wells up from below. The other is the addition of fluids, such as water.
