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
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