GLACIERS

CHAPTER 11

GEOLOGY

10. Approximately 10 percent of the Earth is covered by glaciers; during the last Ice Age, they covered one-third of the Earth’s surface.9. Glacier ice is the largest reservoir of fresh water on the planet, storing an estimated 75 percent of the world’s supply.8. Glaciers are found in 47 countries.7. A glacier can range in length from the equivalent of a football field to more than 100 miles.6. The Antarctic ice sheet is actually a glacier and has existed for at least 40 million years. If it were to melt in its entirety, sea levels would rise 210 feet worldwide, according to the U.S. Geological Service.

Top 10 glacier facts

5. Though it sits on the equator, Mount Kilimanjaro is glaciated.4. On steep slopes, a glacier can be as thin as 50 feet.3. Mountain valleys are typically “V” shaped before being taken oven by a glacier; during glaciation, the valley widens and deepens and thus becomes “U” shaped.2. A single glacier ice crystal can grow to be as large as a baseball.1. Alaska is estimated to have more than 100,000 glaciers. Most remain unnamed

World glaciers

What is a glacier?

a thick mass of moving ice

http://www.jadecoast.ca/Sawyer%20glacier.JPG

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

Trans Labrador Highway

Snow to firn to glacial ice

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

Kelly’s IslandGlacial grooves

Glacial polish

TYPES OF GLACIERS

• Alpine (Valley)Glaciers – glaciers that form at high elevation in mountain valleys

• Ice sheets or Continental Glaciers form in polar regions such as Greenland and Antarctica.

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 1500 feet 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

VALLEY GLACIER

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

till

outwash

Erratics

•Boulders carried great distance by the glacier

•Don’t match surrounding rock

•“strange rock”

Erratics along Lake Michigan Shoreline

TYPES OF GLACIERS

• Alpine (Valley)Glaciers – glaciers that form at high elevation in mountain valleys

• Ice sheets or Continental Glaciers form in polar regions such as Greenland and Antarctica.

MORAINES

• Deposited along edge of glacier during melting

• Ridges of till• Terminal- very end of

glacier• Lateral- side of glacier• Recessional-

progresses behind terminal

MORAINES

• MADE OF TILL

http://www.helsinki.fi/~jhyvonen/PB/M/Cerro%20Tronador%20moraine-pp.JPG

terminal moraine – unsorted sediments deposited at the edge of the melting glacier

Ground Moraine- flat till deposits between recessional moraines

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.

Drumlins

• Hills of sediment deposited by the glacier- till

Boyne, Nubs Nob, Irish Hills are drumlins in MI

MI Drumlins

KAMES

Cone shaped deposits

Deposited at end of meltwater streams

Stratified drift

Mt. Holly is a kame

ESKERS

• Meandering ridges of stratified drift

• Deposited by meltwater streams

• Mined for gravel

Mason esker

Mt. Brighton

Kettle Lakes

• Made from ice blocks

• Deep inland lakes• rocky

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.

Outwash plain

• From melt water (lake) in front of ice

• Flat; sandy

• Contains outwash and often kettle lakes

Pleistocene Epoch“Ice Age”

2my- present

1.5 mya

mastodon

Mammoth

• Bigger than mastodon

• Curvy tusk

When the climate cooled…

Ice advanced over the land, moving southward from Canada over the Great Lakes Region.

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 the river valley – widening and deepening them to form today’s lake bottoms.

Why do scientists believe that glaciers once covered Michigan?

Moraine Deposits =unsorted sediments

• What can deposit unsorted sediment?

Mass movement?

ice

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

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

Isostatic (crustal) reboundland is rebounding up from weight

of glacierabout 53 cm/ century

Pictured Rocks

Kettle Lakes

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

What glacier evidence do we see in Grosse Pointe?

• Erratics• Old beach ridges

– Ridge road– Mack avenue

• Till

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