1GY 301: GeomorphologyGY 301: GeomorphologyLecture 23: Glacial Geomorphology 2: Continental Glaciers UNIVERSITY OF SOUTH ALABAMAhttp://www.indiana.edu/~librcsd/etext/hoosier/image/rm-01.jpgLast TimeGlacial 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 ErosionHead area features•Cirques•Arêtes•Horns•Tarns•Pater Noster lakeshttp://virtual.yosemite.cc.ca.us/ghayes/Tuolumne_Meadows_Field_Trip_files/image024.jpgAlpine Glaciers and ErosionToe area features•U-shaped valleys•Truncated spurs•Hanging valleyshttp://virtual.yosemite.cc.ca.us/ghayes/Tuolumne_Meadows_Field_Trip_files/image024.jpg2Alpine Glaciers and DepositionIn alpine settings, most till is deposited in linear deposits called moraines•Lateral moraine•Medial moraines•Terminal moraines•Recessional morainesToday’s LectureGlacial Geomorphology (Continental variety)• Continental glaciers today and in the past• Erosive features• Depositional featuresTypes of Glaciers• Alpine: rivers of ice that flow through valleys to lower elevations• Continental: large ice masses that cover significant portions of continents and are a mile or more thick• Currently only 2 large continental glaciers exist: the Greenland and Antarctic ice sheets (but there are a few smaller ice caps; e.g., Baffin Island)Continental Glaciers• Thick ice masses actually depress the lithosphere below sea levelhttp://opa.yale.edu/images/articles/6449-E-Oice.jpgIce Shelves• Large portions of continental glaciers that are floating in the oceansThe Ice Age• 18,000 years ago, the last glacial maximum covered all of Canada and a good chunk of Europe in a continental glacier.3• Polished and striated bedrock• Roche moutoneeContinental Glaciation and Erosionhttp://education.usgs.gov/schoolyardhttp://upload.wikimedia.org/wikipedia/commons• Polished and striated bedrock• Roche moutoneeContinental Glaciation and Erosionhttp://www.swisseduc.ch/glaciers/glossary/icons/roche-moutonnee.jpghttp://libwiki.mcmaster.ca/clip/uploads/Main/rocheformation.jpgContinental Glaciation and Deposition• Landforms are produced by the motion of a thick ice sheet Moraines Drumlins Eskers Erratics Outwash Kettle Lakes/Kames Varves LoessContinental Glaciation and Deposition• Moraines produced by continental glaciers are the same as those produced by alpine glaciers….only larger.Oak Ridges Moraine Continental Glaciation and Deposition• Drumlins are deposits of till produced underneath continental glaciershttp://www.geography-site.co.uk/pages/physical/glacierhttp://www.drumlinarealandtrust.org/images/drumlins.jpghttp://geopanorama.rncan.gc.ca/calgary/geotour/6_e.phpContinental Glaciation and Deposition•Eskersare also deposits of till produced underneath continental glaciers, but associated with melt waterhttp://z.about.com/d/geology/1/0/E/L/esker.jpghttp://www.paddling.net/sameboat/Images/esker.gifJenkins eskerBedshiel esker4Continental Glaciation and Deposition• Erratics are large boulders deposited randomly on the Earth’s surface by the conveyor belt action of continental glaciers.http://gsc.nrcan.gc.ca/landscapes/photos/slave_natmap/img0036.jpgContinental Glaciation and Deposition•Outwashplains are large areas of deposition produced during by meltwater.http://www.soils.umn.eduhttp://geoimages.berkeley.eduContinental Glaciation and Deposition• Kames are Kettle Lakes frequently occur together.http://nevis.k12.mn.us/ http://www.climatechange.umaine.eduContinental Glaciation and Deposition• Kettle Lakes are water-filled depressions caused by a “block” of glacial ice trapped in outwash.Kettle LakeContinental Glaciation and Deposition• Kames are piles of sediment originally deposited in depression on the ice that falls as a pile when the ice melts.KameContinental Glaciation and Deposition• Varves are laminated silt layers deposited in glacial lakes. http://www.backyardnature.net/loess/vertbluf.jpghttp://brianmillerphoto.comhttp://www.geologyrocks.co.uk/system/files/u2/varves.jpg5Continental Glaciation and Deposition•Loessis wind blown silt deposited on alluvial plains a long way from the glacier.http://www.backyardnature.net/loess/vertbluf.jpghttp://landcovertrends.usgs.govUpcoming StuffHomeworkAlpine Glaciation Lab(due Friday)Next Lecture: More Continental GlaciationsFriday’s Lab: Map interpretation (continental