GEO 1111 Lecture Notes - Lecture 11: Flux Melting, Pumice, High Island

• School: University of Ottawa
• Department: Geology
• Course: GEO 1111
• Professor: Robert Jack Cornett

Document Summary

Melting a rock: raise temperature - hotspots, decrease pressure (water is an exception) spreading ridge, move phase boundaries subduction zone. Magma and igneous rocks are formed at hotspots, spreading ridges and subduction ones. The only liquid part of the earth is the outer core, no magma being produced at depth. Classified bases on texture and composition (see table on powerpoint) Composition is based on silica content: ultramafic (less than 45%, mafic (45-52%, intermediate (52-66%) ex : diorite, felsic (more than 66%) ex: granite. Magma is less dense than rock, moves upwards. Magma that erupts and reaches surface is called lava. Lavas crystallize to form extrusive (volcanic) rock. Most magmas crystallize before reaching surface and form intrusive (plutonic) rocks. While cooling mafic magmas, he found that minerals crystallized and settled out of the magma as a definite sequence, starting with olivine and feldspars, and ending with quartz.