UNIVERSITY OF SOUTH ALABAMA Last time GY 111 Physical Geology Last bit about Metamorphism A Metamorphic Facies B Shock Metamorphism C Retrograde Metamorphism Lecture 30 Mountain Building 1 Isostacy and Thrusting Metamorphic facies Metamorphic facies Temperature The Problem High Low slate ist Consider conditions of Pressure and Temperature rather than parent rock composition gneiss Parti al sch melti ng phyllite t schis The Solution Blue Pressure granite Gneiss Hornfels facies Granulite Shale Rhyolite Granite Zeolite facies Amphibolite High Grade Metamorphic rock Greenschist Parent rock Eclogite facies High Metamorphic facies Metamorphic facies High High em eta mo rph ism High gra de me tam orp his m Parti al rog rad Pressure Re tro melti ng urv e p Parti al Pressure Bu rial c Temperature Low melti ng Temperature Low High 1 Mountain Belts Today s Agenda Mountain Building 1 A Distribution of mountain belts the return of plate tectonics B Isostasy and the Rock Cycle again C Thrust Faults in the Rockies movie Web notes 30 Mountain Belts Mountain Belts Mountain Belts Mountain Belts Northern Transect New Mountains Southern Transect Old Mountains 2 Mountain Belts The older the mountain range the more time erosion and weathering has had to destroy the mountains Mountain Belts The older the mountain range the more time erosion and weathering has had to destroy the mountains The northern Appalachian Mountains are older than the southern Appalachian Mountains 500 MA versus 300 MA so it stands to reason that they would be more eroded Mountain Belts The older the mountain range the more time erosion and weathering has had to destroy the mountains The northern Appalachian Mountains are older than the southern Appalachian Mountains 500 MA versus 300 MA so it stands to reason that they would be more eroded Isostasy Isostacy The depression of the asthenosphere beneath mountain belts due to loading followed by rebounding as erosion occurs The surprising thing is that the southern Appalachians are still mountains after 300 Million Years of erosion Why are the mountains still there Isostasy Isostacy The depression of the asthenosphere beneath mountain belts due to loading followed by rebounding as erosion occurs Isostasy Isostacy The depression of the asthenosphere beneath mountain belts due to loading followed by rebounding as erosion occurs erosion Styrofoam sheets on water 3 Isostasy Isostacy The depression of the asthenosphere beneath mountain belts due to loading followed by rebounding as erosion occurs Isostasy Isostacy The depression of the asthenosphere beneath mountain belts due to loading followed by rebounding as erosion occurs erosion isostasy Isostasy Isostacy The depression of the asthenosphere beneath mountain belts due to loading followed by rebounding as erosion occurs Isostasy Isostacy The depression of the asthenosphere beneath mountain belts due to loading followed by rebounding as erosion occurs erosion isostasy Isostasy Isostacy The depression of the asthenosphere beneath mountain belts due to loading followed by rebounding as erosion occurs Isostasy Isostacy When you build up mountains depression of the asthenosphere produced continental roots below the continental crust isostasy 4 Isostasy Isostacy Isostasy will continue as long as continental roots still exist Once isostasy stops the mountains will get completely eroded away it takes about 500 MA for this to occur The Rock Cycle Mountain belts involve all types of rocks and minerals and all types of geological processes For example consider the Himalayan Mountains The Rock Cycle The Rock Cycle The Rock Cycle Thrust Faulting in the Rockies So in conclusion mountain building and mountain erosion are excellent examples of the rock cycle in action Incidentally mountain building is itself cyclic see you in GY 112 Movie time 5 Today s Homework 1 Start Prepping for the Final Exam Next Time 1 Mountain building part 2 Appalachians 6
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