GLACIERS
CHAPTER 5
HONORS EARTH SCIENCE
What is a glacier?
a thick mass of moving ice
http://www.jadecoast.ca/Sawyer%20glacier.JPG
How do glaciers form?
Step 1: Snow accumulates.
More snow falls during the winter than melts in the
summer.
Trans Labrador Highway
Step 2: Snow changes to firn.
As snow accumulates, its weight compress
the individual snowflakes to form
firn.
FIRN
http://www.gsw.edu/~bcarter/physgeol/glac/firn.jpg
Firn
http://crevassezone.org/Photos/Graphics/3441L-(Firn).jpg
Step 3: Firn is compressed to form solid glacial ice.
http://patti.tensegrity.net/album/alaska/thompson/ice4.jpg
http://www.asf.alaska.edu:2222/img/firn_diagram.gif http://207.239.98.44/IcelandI%20232.jpg
Step 4: The ice begins to move.
Plastic flow- weight of glacier moves out like pancake batter
http://www-math.science.unitn.it/Bike/Countries/Europe/Tour_Reports/Tour_of_the_Alps/Gallery/glacier.jpg
When the climate cooled…
Ice advanced over the land, moving southward from Canada over the Great Lakes Region.
Glaciar Perito Moreno, in Santa Cruz province, Argentina. It hasn’t happened since 1988 and it is said to be one of the most extraordinary natural events in the world.
- Roberto Cerrudo
Glacier terms
• Zone of Ablation- melting• Zone of Accumulation- snow accumulates
• Crevasse- cracks
• Advance- more accumulation than melting• Retreat- more melting than accumulation
VALLEY GLACIER
How do glaciers erode the surface?
• Plucking –freeze/thaw process lifts particles into ice
Striations- parallel scratches made from rocks in ice scraping against bedrock
Granite Island, Lake Superior MI
Calumet, MI
N47°14’77’’ W88°26’82’’
Kelly’s IslandGlacial grooves
TYPES OF GLACIERS
• Alpine (Valley)Glaciers – glaciers that form at high elevation in mountain valleys
• Ice sheets or Continental Glaciers.
http://daac.gsfc.nasa.gov/DAAC_DOCS/geomorphology/GEO_9/geo_images_9/Fig9.20.gif
Cirque
• A bowl-shaped depression located where a glacier begins to form
http://crevassezone.org/Photos/Graphics/4163L-(Cirque).jpg
Horn
• A tall, pointed rock peak left at the top of a mountain
http://www2.nature.nps.gov/geology//parks/glac/car0348.jpg
Kinnerly Peak - Glacier National Park
The most famous horn in the Alps… The Matterhorn
• Located on the boundary between Switzerland and Italy, the Matterhorn’s summit is 4478 m above sea level.
Arete – spines or ridges of rock that separate glacial valleys
U-shaped Valley - Yosemite National Park
V-shaped valleys become U-shaped valleys as glaciers move through them…
A typical river valley
Over time, running water cuts a deeper V-shape.
Step 1 Step 2
Step 3 Step 4Glacier fills valley, widening and straightening the channel
Glaciers melt leaving a U-shaped valley
Glaciers pick up lots of sediment as they advance over the land.
http://www.geographyjim.org/Newzealandglacier.jpg
TYPES OF GLACIAL DRIFT(Sediments)
• TILL- unsorted; deposited by ice
• STRATIFIED DRIFT- layered; deposited by meltwater streams
• OUTWASH- sorted sand; deposited by meltwater
Erratics
•Boulders carried great distance by the glacier
•Don’t match surrounding rock
Erratics along Lake Michigan Shoreline
TYPES OF GLACIERS
• Alpine (Valley)Glaciers –
• Ice sheets or Continental Glaciers form in polar regions such as Greenland and Antarctica.
MORAINES
• MADE OF TILL• Deposited along edge of glacier during melting
http://www.helsinki.fi/~jhyvonen/PB/M/Cerro%20Tronador%20moraine-pp.JPG
MORAINES
• Terminal- very end of glacier
• Lateral- side of glacier• Recessional-
progresses behind terminal
terminal moraine –
Ground Moraine- flat till deposits between recessional moraines
Kettle Lakes
• Made from ice blocks
Kettle Lakes
• Kettle lakes form when blocks of ice break off the front edge of a glacier, become buried by sediment. The ice melts leaving a hole which fills with water creating a lake.
Drumlins
• Hills of sediment deposited by the glacier- till
Drumlin Formation
ESKERS
• Winding ridges of stratified drift
• Deposited by meltwater streams
• Mined for gravel
KAMES
Cone shaped deposits
Deposited at end of meltwater streams
Stratified drift
Mined for gravel
What glacial landform are the arrows pointing to?
Why do scientists believe that glaciers once covered Michigan?
Moraine Deposits =unsorted sediments
• What can deposit unsorted sediment?
Mass movement?
ice
Moraine Deposits = unsorted sedimentsMoraines are made of unsorted sediments.
Only mass movements and glaciers deposit
unsorted sediments.
Since there are no large hills or
mountains in Michigan for this sediment to fall
down, it must have been deposited by the
glaciers.
Moraine Deposits have the same shape as the Great Lakes.
• Michigan moraines run parallel to the shoreline.
• The same process that formed the moraines formed the Great Lakes.
3 ice lobes
Each of the Great Lakes began as a river.
Image from Earth Science, Tarbuck and Lutgens, 2003
As the climate cooled…
• The rivers froze.
• Glaciers moved through them – widening and deepening them to form today’s lake bottoms.
When the climate began to warm, the glaciers began to melt and retreat.
http://www.msstate.edu/dept/geosciences/CT/TIG/WEBSITES/LOCAL/Spring2002/Michael_Marsicek/images/Great_Lakes_Formation.gif
The Glacial History of Michigan
• The depth of the lake is determined by the thickness of the ice at the time of glaciation. The farther north the lobe of ice, the thicker it was.
• Consequently, the lakes get more shallow in the southern Great Lakes region.
LAKE: GREATEST DEPTH:
• Superior = 1,333 ft.• Michigan = 925 ft.• Huron = 725 ft.• Ontario = 283 ft.• Erie = 212
ft.
The fresh water from the melting glaciers filled in the deep U-shaped valleys that they had carved and
turned them into the lakes we have today.
http://www.ofps.ucar.edu/gapp/networks/images/greatlakes_map.jpg
What other evidence do we have that glaciers once covered our state?
• Depositional features such as drumlins and kettle lakes.
Kalkaska, Michigan
Kettle Lakes
Boyne Mountain
What glacier evidence do we see in Grosse Pointe?
• Erratics• Old beach ridges
– Ridge road– Mack avenue
• Till
http://homepage.tinet.ie/~jconsidi/BWS/karst4.jpg
Isostatic rebound
• The land is rebounding once the weight of the glacier left
• 3 cm/year
Isostatic reboundPictured Rocks
Glacial polish
Why do scientists believe that glaciers once covered Michigan?
• Michigan is covered with till
• The moraine deposits follow the outline of Great Lakes
• Erratics
• Striations
• Isostatic rebound
• Glacial polish
Resources• http://cse.cosm.sc.edu/erth_sci/Erosion/plucking.jpg
• http://www.skidmore.edu/academics/geo/courses/ge101/Pictures/Glaciers/GlacialStriations.jpg
• http://www.go2moon.com/image/Valdez-Glacier.jpg
• http://www.glaciers.pdx.edu/kennicott/photos99/glacier.jpg
• http://www.brownbearsw.com/photos/pws/moraine.jpg
• http://www.homepage.montana.edu/~geol445/hyperglac/depproc1/moraine.JPG
• http://www.ucalgary.ca/~dgsmit/MORAINE.jpg
• http://mac01.eps.pitt.edu/harbbook/c_viii/images/icefields/Hwb0530.GIF
• http://www.geographyhigh.connectfree.co.uk/s3glacgeoghigh34b.gif
• http://www.uwsp.edu/geo/faculty/lemke/images/lithosphere/drumlin_diagram_small.gif
• http://online.sd43.bc.ca/della/images/drumlin.jpg
• http://www.geology.wisc.edu/~qlab/g420/drumlin.jpg
• http://www.bbc.co.uk/scotland/education/bitesize/standard/img/geography/glaciation/g98.gif
• http://pbisotopes.ess.sunysb.edu/esp/Science_Walks/carmans/kettle-hole.gif
• http://perth.uwlax.edu/faculty/stoelting/Intro/Guides/Images3/southern_Kettle_Moraine_lakes_WI_800.jpg
• http://images3.vrbo.com/vrbo/images/18982c.jpg• http://www.on.ec.gc.ca/greatlakeskids/images/g_lakes_form.gif• http://wrgis.wr.usgs.gov/docs/parks/glacier/UvalleyB.gif• http://wrgis.wr.usgs.gov/docs/parks/glacier/UvalleyC.gif• http://www.jchl.co.uk/photos/greenland/Valley.jpg• http://www.emporia.edu/earthsci/student/martel1/ice.jpg• http://wrgis.wr.usgs.gov/docs/parks/glacier/gifJPGdisplay.html• http://www.uwsp.edu/geo/faculty/lemke/alpine_glacial_glossary/images/
more_examples/canada_cirque01_dh.jpg• http://www.uoregon.edu/~millerm/Kluane1.jpeg• http://people.surfaceeffect.com/pete/photos/folksholiday/yosemitevalley/
valley2.jpg• http://www.theotherpages.org/images/image200.jpg• http://www.northforkmedia.com/spiveyscience/images/glacialerosion/
pages/grinnellcirqueareteetc_jpg.htm• http://www3.uakron.edu/modlang/97trip/d16f.jpg• http://tvl1.geo.uc.edu/ice/Image/icland/Greenland.html• http://www.bougerolle.net/photos/matterhorn.jpg
• http://perth.uwlax.edu/faculty/stoelting/Intro/Guides/Images3/glacial_erratics_Lake_Michigan_WI_800.jpg
• http://www.fettes.com/Cairngorms/images/Easter_Island.jpg
• http://rt23.com/Scenery/spring/images/tripod_rock.jpg
• http://ic.ucsc.edu/~rocks/eart109/Photo_Composition/Top_Pothole.jpg
• http://perth.uwlax.edu/faculty/stoelting/Intro/Guides/Images3/southern_Kettle_Moraine_lakes_WI_800.jpg