1GY 301: GeomorphologyGY 301: GeomorphologyLecture 22: Glacial Geomorphology 1: Alpine Glaciers UNIVERSITY OF SOUTH ALABAMAhttp://www.roberts-1.com/t/s07Last TimeGlaciers and Glacial Mechanics• Types of glaciers (alpine)• Formation of glacial ice• Movement of iceGlaciersGlaciers are thick masses of ice that originate on land through the accumulation of snow.http://media-cdn.tripadvisor.com/media/photo-s/01/25/4a/ee/in-the-mountains-above.jpgAll that is required is for more snow to fall in the cold winter months than melts in the warm summer months.GlaciersGlaciers are thick masses of ice that originate on land through the accumulation of snow.SnowFirnGlacial Icehttp://www.ig.utexas.eduGlaciers form through a 3 step processAlpine Glaciershttp://www.scienceclarified.com/images/uesc_05_img0282.jpgAlpine or Valley Glaciers(Zone of Accumulation; Zone of Wasting/Ablation, Calving,)http://stloe.most.go.th/html/lo_index/LOcanada3/305/images/5_2.jpgIce MovementIce moves down slope from the zone of accumulation to the zone of ablation due to a combination of plastic flow and basal slip.http://nevis.k12.mn.us/academics/science/glacier_hor_profile1.jpg2Ice MovementIce moves down slope from the zone of accumulation to the zone of ablation due to a combination of plastic flow and basal slip.Firn50 mFlowSlipGeological Effects of GlaciersIce exerts tremendous erosive force on bedrock forming unique geomorphologic features and transporting great quantities of sediment ….… to be continuedhttp://www.kschapterc.org/album-mead/23.jpgToday’s LectureGlacial Geomorphology (alpine variety)• Erosive features• Depositional featuresAlpine Glaciers and ErosionWhen alpine glaciers form and advance, significant changes to the terrain will occurBefore Glaciationhttp://www.uwsp.edu/geo/projects/virtdept/ipvft/arete.htmlAlpine Glaciers and ErosionWhen alpine glaciers form and advance, significant changes to the terrain will occurDuring Glaciationhttp://www.uwsp.edu/geo/projects/virtdept/ipvft/arete.htmlAlpine Glaciers and ErosionWhen alpine glaciers form and advance, significant changes to the terrain will occurDuring Glaciationhttp://www.uwsp.edu/geo/projects/virtdept/ipvft/arete.html3Alpine Glaciers and ErosionHead area features•Cirques•Arêtes•Horns•Tarns•Pater Noster lakeshttp://virtual.yosemite.cc.ca.us/ghayes/Tuolumne_Meadows_Field_Trip_files/image024.jpgChalk BoardAlpine Glaciers and ErosionArêtes on topographic maps… look for sharp ridgeshttp://www.csus.edu/indiv/s/slaymaker/archives/Geol10L/landforms.htmhttp://www.gdargaud.net/Alpine Glaciers and ErosionCirques on topographic maps… look for flat bottomed, steep sided embaymentshttp://www.csus.eduhttp://www.homepage.montana.eduAlpine Glaciers and ErosionHorns on topographic maps… look for sharp sided peakshttp://www.csus.edu/indiv/s/slaymaker/archives/Geol10L/landforms.htmhttp://www.sonata-photographica.comAlpine Glaciers and ErosionTarns/Pater Noster Lakes on topographic maps… look for blue splotches!http://www.csus.edu/indiv/s/slaymaker/archives/Geol10L/landforms.htmhttp://images.absoluteastronomy.com/images/Alpine Glaciers and ErosionToe area features•U-shaped valleys•Truncated spurs•Hanging valleyshttp://virtual.yosemite.cc.ca.us/ghayes/Tuolumne_Meadows_Field_Trip_files/image024.jpgChalk Board4Alpine Glaciers and ErosionU-shaped valleys/truncated spurs on topographic mapshttp://www.csus.edu/indiv/s/slaymaker/archives/Geol10L/landforms.htmhttp://www.geology.wisc.eduAlpine Glaciers and ErosionHanging valleys on topographic maps: look for water fallshttp://www.uwsp.edu/geo/Alpine Glaciers and DepositionWhen alpine glaciers advance they push with incredible force, enough to scrape down to bedrock and push all manner of sediment as they go. Till: unsorted sediment (grain size from clay to huge boulders)Alpine Glaciers and DepositionIn alpine settings, most till is deposited in linear deposits called moraines•Lateral moraine•Medial moraines•Terminal moraines•Recessional moraineshttp://images.encarta.msn.com/xrefmedia/aencmed/targets/illus/ilt/T790634A.gifAlpine Glaciers and Depositionhttp://www.swisseduc.ch/glaciersAlpine Glaciers and DepositionIn alpine settings, most till is deposited in linear deposits called moraines•Lateral moraine•Medial moraines•Terminal moraines•Recessional moraineshttp://www.swisseduc.ch/glaciers5Alpine Glaciers and DepositionIn alpine settings, most till is deposited in linear deposits called moraines•Lateral moraine•Medial moraines•Terminal moraines•Recessional moraineshttp://nsidc.org/glaciers/gallery/images/bylot_island_valley_large.jpgAlpine Glaciers and DepositionMoraines on topographic maps (modern glaciers): look for sediment on icehttp://www.csus.edu/indiv/s/slaymaker/archives/Geol10L/landforms.htmAlpine Glaciers and DepositionMoraines on topographic maps (post glaciation): tricky; look for ridgeshttp://www.csus.edu/indiv/s/slaymaker/archives/Geol10L/landforms.htmUpcoming StuffHomeworkGroundwater and Karst Geomorphology(due tomorrow)Next Lecture: Continental GlaciationsFriday’s Lab: Map interpretation (alpine glaciers)Soup Day TomorrowChicken veggi (w rice)4