Glaciers

used with permission http://tvl1.geo.uc.edu/ice/Glacier.html
Holgate Glacier, Kenai Peninsula, Alaska

Nearly 2% of the water on the earth is currently tied up in glaciers.

There are two type of glaciers. They are

Alpine Glaciers

have small areas but thousands exist
are found at the top of mountains

Continental Glaciers (ice sheets)

vast glaciers found near the earth's poles
Antarctica and Greenland

seeking permission from http://toltec.lib.utk.edu/~cic/mapsourc.htm

How do Glaciers form?

If more snow accumulates (in winter) than melts (in summer), there is a net build-up of snow. (zone of accumulation)
The snow moves downhill past the snow line (>32 degrees) due to gravity (to the zone of wastage)

the snow gets compressed by overlying layers and gets re-crystallized (at about 165 feet) forming a "plastic like" substance (which has a consistency similar to toothpaste)
the top layer of ice remains brittle creating very dangerous cracks called crevasses.
some glaciers move very slowly, but others may move several meters a day.
a large piece of a glacier may break off and fall into the ocean ... creating an iceberg.

A "cool" dude standing where he shouldn't be. Many glacial hikers die each year falling into crevasses. Notice how dirty the ice actually is.

The end of the glacier is called the terminus (or snout). This can be the site of glacial features such as terminal moraines.

The terminus may advance (down the mountain) or retreat (up the mountain) as global climate changes.

Currently, most glaciers are in a state of retreat due to global warming.
This means that more ice is melting (in the zone of wastage) than is accumulating (in the zone of accumulation).
Ice within the glacier is always moving downhill (no matter what the motion of the terminus) ... similar to items moving along a conveyor belt ... however, when the glacier is retreating, the conveyor belt is getting shorter.
Sea level has risen worldwide approximately 15-20 cm (6-8 inches) in the last century. Approximately 2-5 cm (1-2 inches) of the rise has resulted from the melting of mountain glaciers. Another 2-7 cm has resulted from the expansion of ocean water that resulted from warmer ocean temperatures. If all the ice melted, the sea level would rise 60-70 meters (over 200 ft.) This would flood many coastal cities (the movie Water World was way off!).

How Glaciers Alter the Landscape

Continental Glaciers tend to "smooth" the surfaces they move over.

Alpine Glaciers tend to carve out "U" shaped valleys and make mountainous regions more jagged and angular (Matterhorn).

Yosemite Valley (Hey lady .. get out of my picture!)

Permission from http://www.geology.iastate.edu/new_100/hanging.html
Hanging Valleys on the east side of Glacier National Park

with permission from Mad about Mountains by Ann Bowker
The Matterhorn

Alpine features:

Horn (see the picture of the Matterhorn above)
Cirques (bowl shaped depressions)

A Cirque seen close up (Rocky Mountains)

Cirque (sir ... rhymes with jerk) in Austria

Notice the sharp ridge (in front) called an arête "a rett"
which is French for fish bone (I think)

Alpine glaciers become very efficient at "grinding" down mountains

These Striations are grooves in bedrock caused by glacial grinding (Colorado). The ice doesn't do this, it is the rocks within the ice that do the grinding.

This glacial run-off looks white because it contains ground-up rock called "glacial flour". When it settles, it looks like a fine powder. Jasper National Park, Canada

Moraine Lake (the most beautiful place on the earth) Jasper, Canada. Notice the loose sediments at the base of the mountain. This is called talus which (in this case) is mostly from glacial action.

More Talus (Austria)

Glacial Features found in Wisconsin

this

The Great Lakes are a direct byproduct of the last glacial advance (starting about 12,000 BC - 4000 BC). It carved out deep basins into which water filled in. Also the Finger Lakes in NY.

The Ice Age Trail

Permission from iceagetrail.org

This map outlines the terminus of the last glacial advance. It is interesting to note that all of Wisconsin was NOT glaciated. In fact, the entire South-West sector of the state remained glacier free - known as the "driftless region". This is because the advancing glacier hit bedrock which was very resistant and acted like a "wedge" which split the glacier into separate "lobes". At least that is the prevailing hypothesis.

This occurred about 12,000 years ago.

All along this trail, several glacial features may be found.

Kettle Moraine Area - Waukesha County (and surrounding counties to the north and south) glacial area formed by the Green Bay Lobe and Lake Michigan Lobe. It includes moraines, drumlins, kames, eskers, and kettles.

Devil's Lake State Park is a glacial dammed lake and Parfrey's Glen is a canyon which exposes much of the underlying rocks on the south end of the Baraboo range.

This area is where a huge deposit of ancient red quartzite was exposed to the surface. It tells us of a time 1.7 billion years ago that this area was at a continental margin and there was sand all over (and got buried to eventually form the quartzite). The glacier helped expose this rock to the surface. Here is a very good geology history lesson about the area.

Glacial Structures found in Wisconsin

As a glacier moves it sculpts the landscape. In addition, the water that melts off a glacier can do the same. The term drift refers to sediment structures left by glacial action, no matter how it was done.

Any sediments deposited directly by a glacier is known as till. That is, the glacier melts and leaves behind some structured sediments. Because ice usually does not sort the sediments the same way wind and running water can, till is usually an assortment of unsorted (unstratified) drift
Stratified drift are structures sculpted by the action of glacier melt water. Here the particles making up the structure are sorted by size and weight (something water can do quite easily).

Moraines - A ridge like accumulation of till built chiefly along the terminal margin of a valley glacier or the margin of an ice sheet.

permission from http://tvl1.geo.uc.edu/ice/Image/icland/organ.html
Example of a Moraine

Kettles - depressions left by blocks of ice trapped in glacial deposits. When the ice melts it leaves a depression. Many of the lakes in Wisconsin and Minnesota are formed from kettles.

permission from http://tvl1.geo.uc.edu/ice/Image/icpro/643-17.html
Drumlins - Cigar shaped mounds which point in the direction the glacier moved. It is not known exactly how they are formed but most likely as a result of a glacier running over a pre-existing glacial deposit.

The Mihal household which sits smack dab on top of a drumlin. Way cool!

Permission http://www.geo.cornell.edu/geology/classes/Geo101/101images.html click here

Want to see more drumlins? Go peddle your bike on the Glacial - Drumlin State Bike Trail

Kames - Stratified drift deposited in depressions and cavities in stagnant ice and left as steep sided hills when the ice melts. For example, imagine water running on the top of a glacier but suddenly runs down a deep crevasse ... this would be a place where lots of debris could pile up. Holy Hill, Lapham Peak, and Dundee Kame are local examples.

View from Lapham Peak Waukesha WI ( a great place for hiking & X-country skiing)
Just south of I94 exit hwy. C. Who is that sexy lady?

Esker- A winding ridge of stratified drift (mostly sand and gravel). This feature is formed in a glacial tunnel when ice is melting and carrying lots of sediments with the running water. When the ice is all gone you get a ridge of sediments up to 15 m high and kilometers in length. If you live on one of these you may be rich because sand and gravel are valuable building materials

permission from http://tvl1.geo.uc.edu/ice/Image/subland/Bearflute.html

Erratics - A stone or boulder, glacially transported from place of origin and left in an area of different bedrock composition. Some erratics have been moved hundreds ... even thousands of miles. As you drive past a farmers field, look for some huge boulders which look out of place and were too big for the farmer to move ... these are usually erratics.

Great glacier links:

news about glaciers