GLACIERS

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

Mt. Holly

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