GSCI 1051 Lecture Notes - Lecture 8: Lithosphere, Mid-Ocean Ridge, Igneous Rock
Document Summary
Shield volcanoes- broad shallow domes formed by basalt. Calderas form as the top collapses into magma chamber. Stratovolcanoes- volcanoes composed of alternating layers of lava and tephra craters form as the tip of the mountain collapses. Plate boundaries- most volcanism occurs along plate boundaries although it also occurs at hot spots. Divergent plate boundaries: mid ocean ridges- new oceanic crust forms due to decompression partial melting of the mantle forms pillow basalt under water, continental rifts- rifting here produces lavas of various compositions. Convergent plate boundaries: most volcanoes occur here. Oceanic crust releases volatiles as it goes below continental crust intermediate and felsic magmas form as mafic magma melts continental crust. Geology 1051: mantle plumes melt through the lithosphere, creating hot spots such as hawaii, Yellow stone, and iceland: oceanic mid ocean ridge hotspots yield mafic rocks whereas continental ones yield a variety of igneous rock, volcanisms occurs on the moon due to decompression melting.
