UNIVERSITY OF SOUTH ALABAMA Last Time Glacial Geomorphology (alpine variety) • Erosive features GY 301: Geomorphology • Depositional features Lecture 23: Glacial Geomorphology 2: Continental Glaciers http://www.indiana.edu/~librcsd/etext/hoosier/image/rm-01.jpg Alpine Glaciers and Erosion Alpine Glaciers and Erosion When alpine glaciers form and advance, significant changes to When alpine glaciers form and advance, significant changes to the terrain will occur the terrain will occur Before Glaciation During Glaciation http://www.uwsp.edu/geo/projects/virtdept/ipvft/arete.html http://www.uwsp.edu/geo/projects/virtdept/ipvft/arete.html Alpine Glaciers and Erosion Alpine Glaciers and Erosion Head area features Toe area features •Cirques •U-shaped valleys •Arêtes •Truncated spurs •Horns •Hanging valleys •Tarns •Pater Noster lakes http://virtual.yosemite.cc.ca.us/ghayes/Tuolumne_Meadows_Field_Trip_files/image024.jpg http://virtual.yosemite.cc.ca.us/ghayes/Tuolumne_Meadows_Field_Trip_files/image024.jpg 1 Alpine Glaciers and Deposition Today’s Lecture In alpine settings, most till is deposited in linear Glacial Geomorphology (Continental variety) deposits called moraines • Continental glaciers today and in the past • Erosive features •Lateral moraine • Depositional features •Medial moraines •Terminal moraines •Recessional moraines Types of Glaciers Continental Glaciers • Alpine: rivers of ice that flow through valleys to • Thick ice masses actually lower elevations depress the lithosphere • Continental: large ice masses that cover significant below sea level 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) http://opa.yale.edu/images/articles/6449-E-Oice.jpg Ice Shelves The Ice Age • Large portions of • 18,000 years ago, the continental glaciers that last glacial maximum are floating in the covered all of Canada oceans and a good chunk of Europe in a continental glacier. 2 Continental Glaciation and Erosion Continental Glaciation and Erosion • Polished and striated • Polished and striated bedrock bedrock • Roche moutonee • Roche moutonee http://upload.wikimedia.org/wikipedia/commons http://education.usgs.gov/schoolyard http://libwiki.mcmaster.ca/clip/uploads/Main/rocheformation.jpg http://www.swisseduc.ch/glaciers/glossary/icons/roche-moutonnee.jpg Continental Glaciation and Deposition Continental Glaciation and Deposition • Landforms are produced • Moraines produced by the motion of a thick by continental ice sheet glaciers are the same Moraines as those produced by Drumlins alpine glaciers….only Eskers larger. Erratics Outwash Kettle Lakes/Kames Varves Loess Oak Ridges Moraine Continental Glaciation and Deposition Continental Glaciation and Deposition • Drumlins are deposits •Eskersare also deposits of till Jenkins esker of till produced produced underneath underneath continental glaciers, but continental glaciers associated with melt water http://www.geography-site.co.uk/pages/physical/glacier Bedshiel esker http://geopanorama.rncan.gc.ca/calgary/geotour/6_e.php http://www.drumlinarealandtrust.org/images/drumlins.jpg http://z.about.com/d/geology/1/0/E/L/esker.jpg http://www.paddling.net/sameboat/Images/esker.gif 3 Continental Glaciation and Deposition Continental Glaciation and Deposition • Erratics are large boulders deposited randomly on the •Outwashplains are large areas of deposition produced Earth’s surface by the conveyor belt action of during by meltwater. continental glaciers. http://geoimages.berkeley.edu http://www.soils.umn.edu http://gsc.nrcan.gc.ca/landscapes/photos/slave_natmap/img0036.jpg Continental Glaciation and Deposition Continental Glaciation and Deposition • Kames are Kettle Lakes frequently occur together. • Kettle Lakes are water-filled depressions caused by a “block” of glacial ice trapped in outwash. Kettle Lake http://nevis.k12.mn.us/ http://www.climatechange.umaine.edu Continental Glaciation and Deposition Continental Glaciation and Deposition • Kames are piles of sediment originally deposited in • Varves are laminated silt layers depression on the ice that falls as a pile when the ice deposited in glacial lakes. melts. Kame http://www.backyardnature.net/loess/vertbluf.jpg http://www.geologyrocks.co.uk/system/files/u2/varves.jpg http://brianmillerphoto.com 4 Continental Glaciation and Deposition Upcoming Stuff •Loessis wind blown silt deposited on alluvial Homework Alpine Glaciation Lab (due Friday) plains a long way from the glacier. Next Lecture: More Continental Glaciations Friday’s Lab: Map interpretation (continental glaciers) http://www.backyardnature.net/loess/vertbluf.jpg http://landcovertrends.usgs.gov 5.