Recently glaciated
and flooded by
large lake
Never
glaciated
Not
recently
glaciated
Very
recently
glaciated
Not
recently Never
glaciated glaciated
Glaciers and
MN Glacial Geology!
http://samadhisoft.com/wp-content/uploads/2007/11/glacier.jpg
http://ga.water.usgs.gov/edu/earthglacier.html
What is a glacier, exactly?
•
•
•
•
Ice and granular snow
Formed by compaction and recrystallization
Evidence of movement
Land-based
http://www.climbing.com/leadingoff/RuthGlacier256-Irons.jpg
Glacial Ice Formation
1. It snows!
2. Survives the summer
3. Burial and compaction
4. Partial melting and
recrystallization
5. Becomes firn/neve
6. More compaction and
recrystallization
7. Forms glacial ice
(density = 0.8 to 0.9 g/cm3)
http://upload.wikimedia.org/wikipedia/commons/8/87/Glacial_ice_formation_LMB.png
Glacial Ice
http://farm1.static.flickr.com/29/37765722_39a3d9f268.jpg
Glacier Growth
http://www.uwsp.edu/geo/faculty/ritter/images/lithosphere/glacial/glacier_zones.jpg
Glacier Growth
http://www.uwsp.edu/geo/faculty/lemke/geol370/lecture_notes/04_glacial_mass_balance.html
The Equilibrium Line
http://uregina.ca/~sauchyn/geog323/355.jpg
http://www.globalwarmingart.com/wiki/Image:Glacier_Mass_Balance_Map_png
Glacier Movement
The weight of the thick layer of ice combined with gravity's
influence, causes glaciers to flow very slowly. Movement
along the underside of a glacier is slower than movement at
the top due to the friction created as it slides along the
ground's surface.
http://nsidc.org/glaciers/questions/move.html
NOT a glacier!
Two Main Types of Glaciers
Continental Glaciers
Alpine Glaciers
http://thedude.com/images2/thule_jim_ice_cap.jpg
http://nsidc.org/glaciers/gallery/junoField_ogives.html
Alpine Glaciers
• Form high in mountain valleys and often extend many
kilometers down the valley.
• Resemble river systems.
• Great eroders, forming many familar features:
• aretes
• horns
• cirques
• hanging valleys
• truncated spurs
• U-shaped valleys
http://www.indiana.edu/~g103/G103/Week8/week8.html
Alpine Glaciers
http://www.girr.org/vacation_diaries/camping_2004/hanging_valley.jpg
http://www.uwsp.edu/geo/faculty/lemke/geol370/images/09_cirque_arete_molnia2.jpg
aretes, cirques, horns
hanging valley,
truncated spur
Alpine Glaciers:
U-shaped Valleys & Fjords
http://www.gly.uga.edu/railsback/FieldImages/ObergurglGaisbergU.jpeg
http://facstaff.colstate.edu/buttler_douglas/projects/le
arningMod/Austral_Realm_v3/before_files/image016.
jpg
Continental Glaciers
http://www.gly.uga.edu/railsback/FieldImages/ObergurglGaisbergU.jpeg
http://cgc.rncan.gc.ca/baffin4d/proj/images/gallery/zdanowicz_3.jpg
Continental Glaciers
http://www.ufoarea.com/aas_antarcticamoving.html
http://www.fvalk.com/images/Earth_hrpt/Winter/Greenland-10!.gif
We can figure out where glaciers have
been from the deposits they leave behind…
North Shore 2004
Carrie Jennings, MN Geological Survey, U of MN, 2008
…and by looking at modern processes.
Carrie Jennings, MN Geological Survey, U of MN, 2008
As in Antarctica,
the ice lobes of
the Laurentide
Ice Sheet were fed
by ice streams
Carrie Jennings, MN Geological Survey, U of
“Prairie Ice Streams”
Carrie Jennings, MN Geological Survey, U of
MN, 2008
Manitoba
Satellite
Radar
allows a
close-up
view of the
ice streams
that fed the
lobes that
entered
Minnesota.
Carrie Jennings, MN Geological
Survey, U of MN, 2008
Look again at the ice stream in West Antarctica.
Carrie Jennings, MN Geological Survey, U of MN, 2008
And compare to the James
and Des Moines lobes in the
Dakotas and Minnesota.
Carrie Jennings, MN Geological Survey, U of MN, 2008
The base of these ice streams are dynamic, exciting, and….FLAT!
Carrie Jennings, MN Geological Survey, U of MN, 2008
Wisconsinan Glacial Lobes
Basal Ice - Debris-rich
Carrie Jennings, MN Geological Survey, U of MN, 2008
Carrie Jennings, MN Geological Survey, U of MN, 2008
…Form Till Deposits
Carrie Jennings, MN Geological Survey, U of MN, 2008
Carrie Jennings, MN Geological Survey, U of MN, 2008
…and erratics
http://www.geo.cornell.edu/geology/classes/Geo101/graphics/madison.jpg
Moraines
http://www.swisseduc.ch/glaciers/glossary/icons/terminalmoraine.jpg
http://academic.emporia.edu/aberjame/ice/lec08/lec8.htm
Drumlins
http://www.winona.edu/geology/MRW/mrwimages/drumlin2.jpg
http://www.winona.edu/geology/MRW/mrwimages/Drumlin_Alberta.gif
http://www.winona.edu/geology/MRW/mrwimages/Drumlin_Alberta.gif
Glacial Lake Deposits
Carrie Jennings, MN Geological Survey, U of MN, 2008
Glacial Lake Deposits
Carrie Jennings, MN Geological Survey, U of MN, 2008
Kettle Lakes
• Ice blocks that get
stranded, then
buried by sediment
will create the
classic kettle lake.
Carrie Jennings, MN Geological Survey, U of MN, 2008
Kettle Lakes
http://darkwing.uoregon.edu/~millerm/MNKettles.jpeg
Herzfeld, 1998, Bering Glacier
Carrie Jennings, MN Geological Survey, U of MN, 2008
Carrie Jennings, MN Geological Survey, U of MN, 2008
Icebergs
Carrie Jennings, MN Geological Survey, U of MN, 2008
Iceberg Drag Marks
Carrie Jennings, MN Geological Survey, U of
MN, 2008
Polishing and
Scouring
http://www.winona.edu/geology/MRW/Quaternary.htm
“Everywhere you look in MN you
can see the effects of the last
glaciation. The landscape tells
the story and we are still learning
to read it. You can help.”
- Carrie Jennings, MN Geological Survey