GLACIERS CHAPTER 5 HONORS EARTH SCIENCE

What is a glacier? a thick mass of moving ice

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

Firn

Step 3: Firn is compressed to form solid glacial ice.

Step 4: The ice begins to move. Plastic flow- weight of glacier moves out like pancake batter

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

pine_glacier_processes_side_view_800.jpg 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 Island Glacial grooves

Glaciers pick up lots of sediment as they advance over the land.

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.

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Cirque A bowl-shaped depression located where a glacier begins to form

Horn A tall, pointed rock peak left at the top of a mountain 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 3Step 4 Glacier fills valley, widening and straightening the channel Glaciers melt leaving a U-shaped valley

Hanging Valley a small valley that has not eroded as deep as the main valley that it is connected to Waterfalls often form at hanging valleys.

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 – 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 Terminal- very end of glacier Lateral- side of glacier Recessional- progresses behind terminal

MORAINES MADE OF TILL- unsorted sediment

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

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

Outwash plain

What glacial landform are the arrows pointing to?

Why do scientists believe that glaciers once covered Michigan?

Moraine Deposits = unsorted sediments Moraines 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.

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.

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.

What other evidence do we have that glaciers once covered our state? Depositional features such as drumlins, eskers and kettle lakes. Kalkaska, Michigan

Kettle Lakes

Glacial polish

Why do scientists believe that glaciers once covered Michigan? Michigan is covered with unsorted moraine deposits. The moraine deposits follow the outline of Great Lakes.. Erratics/ glacial polish striations Other glacial landforms (kettles, drumlins, eskers, kames….)

Isostatic rebound The land is rebounding once the weight of the glacier left 3 cm/year

Isostatic rebound Pictured Rocks

Resources riations.jpghttp:// riations.jpg gifhttp:// gif n/g98.gifhttp:// n/g98.gif

e_Moraine_lakes_WI_800.jpghttp://perth.uwlax.edu/faculty/stoelting/Intro/Guides/Images3/southern_Kettl e_Moraine_lakes_WI_800.jpg e_examples/canada_cirque01_dh.jpghttp:// e_examples/canada_cirque01_dh.jpg ey2.jpghttp://people.surfaceeffect.com/pete/photos/folksholiday/yosemitevalley/vall ey2.jpg grinnellcirqueareteetc_jpg.htmhttp:// grinnellcirqueareteetc_jpg.htm

_Lake_Michigan_WI_800.jpghttp://perth.uwlax.edu/faculty/stoelting/Intro/Guides/Images3/glacial_erratics _Lake_Michigan_WI_800.jpg e_Moraine_lakes_WI_800.jpghttp://perth.uwlax.edu/faculty/stoelting/Intro/Guides/Images3/southern_Kettl e_Moraine_lakes_WI_800.jpg