UT Arlington GEOL 1113 - mountains, mountain building, & growth of continents

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PowerPoint PresentationSlide 2Slide 3Slide 4Slide 5Slide 6Slide 7Slide 8Slide 9Slide 10Slide 11Slide 12Slide 13Slide 14Slide 15Slide 16Slide 17Slide 18Slide 19Slide 20QuickTime™ and aTIFF (Uncompressed) decompressorare needed to see this picture.mountains, mountain building, & growth of continentsQuickTime™ and aTIFF (Uncompressed) decompressorare needed to see this picture.mountains and mountain buildingmountain belts• are chains of mountains 1,000’s of km’s long• sit at or near edges of continents• form from tectonic or volcanic processesover millions of years--geosphere• erode as they grow higher and steeper--hydrosphere• cause precipitation as air rises above them--atmospheremountains and mountain buildingmountain beltsare very longcompared to their widthNorth AmericanCordilleraextends fromAlaskatoPanamamountains and mountain buildingmountain beltsheight is related to age: old mountains (100’s of millions of years) (Appalachians) have lower elevations (due to erosion) than young mountains (a few million years) (Himalayas)QuickTime™ and aTIFF (Uncompressed) decompressorare needed to see this picture.QuickTime™ and aTIFF (Uncompressed) decompressorare needed to see this picture.mountains and mountain buildingancient mountain beltseroded flat: form stable, interior of continents: craton-- oldest parts are shields -- e.g. Canadian shieldQuickTime™ and aTIFF (Uncompressed) decompressorare needed to see this picture.mountains and mountain buildingmountain belts• thick sequences of folded and faulted rocks --typically marine (formed in ocean) sedimentary rocks• metamorphic rocks locally commonmountains and mountain buildingmountain belts• fold and thrust belts --crust shortened and thickened(remember: thrust faults indicate shortening)• common at convergent boundaries (compression)Himalayas, Alps, Urals, northern and Canadian RockiesQuickTime™ and aTIFF (Uncompressed) decompressorare needed to see this picture.green arrow shows Lewis Thrust, Glacier National Parkmountains and mountain buildingmountain beltsfold-thrust mountainsevolution of mountain beltsmountains and mountain buildingaccumulation stagerocks (sedimentary) that will later be uplifted, faulted, andfolded into mountains aredeposited in opening ocean(sea floor spreading)mountain building episode from plate convergence(provides compression necessary for thrusting)orogenic stageQuickTime™ and aTIFF (Uncompressed) decompressorare needed to see this picture.Mt. EverestQuickTime™ and aTIFF (Uncompressed) decompressorare needed to see this picture.Himalayan foothillsQuickTime™ and aTIFF (Uncompressed) decompressorare needed to see this picture.Swiss Alpsmountains and mountain buildingevolution of mountain beltswhen mountains get very tall (e.g. Himalayas), gravitational collapse and spreading may occur--normal faulting and extension/thinning of crust--uplift of metamorphic rocks from depth as crust thins and spreadsmountains and mountain buildingevolution of mountain beltsafter convergence stops, erosion and uplift occur--isostatic adjustment--to thin continental rootmountains and mountain buildingevolution of mountain beltsuplifting crust spreads and results in tension (extension)that produces normal faulting and createsfault-block mountains(horsts and grabens from normal faulting)evolution of mountain beltsfault-block mountainsmountains and mountain buildingBasin and Range, western USQuickTime™ and aTIFF (Uncompressed) decompressorare needed to see this picture.topographyQuickTime™ and aTIFF (Uncompressed) decompressorare needed to see this picture.QuickTime™ and aTIFF (Uncompressed) decompressorare needed to see this picture.QuickTime™ and aTIFF (Uncompressed) decompressorare needed to see this picture.Basin and Rangeevolution of Basin and Rangemountains and mountain buildingcrustal extension dominates today--accompanied by high heat flow--older period of thrusting andformation of mountains whencontinental root developeddelamination of mantle?mantle lithosphere detachesand sinks into asthenospherewarm asthenospherefills space and results instretching of crust but must explain high heat flowuplift and erosion yield extensionmodern Basin and Rangemountains and mountain buildingextension at surface; upwelling asthenosphere at depthcontinents grow as mountain belts evolve at active continental marginsmountains and mountain buildingigneous activity addsnew crustsedimentary rocksoriginally deposited in oceanare uplifted, folded,and faulted toform new terranesthat are “accreted”or added tocontinent along its edgeaccreted terranes inwestern UScontinents decrease in age toward their margins continental growthgeologic map of the United StatesPaleozoic to Recent orogenic belts Paleozoicorogenic belts(Appalachians)Canadian shield Paleozoicorogenic belts(Ouachitas, Marathons)Mesozoic to Recentpassive marginPaleozoicto Recent active marginfrom: http://pubs.usgs.gov/publications/textBasin and Range(rifting)growth of continents: US examplecratonon-going subduction(Cascadia)transformboundary(San


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