GLACIERS – RIVERS OF ICE!

Interesting facts (via http://www.nsidc.org ):

· Presently, 10% of land area is covered with glaciers.

· Glaciers store about 75% of the world's freshwater.

· Antarctic ice is over 4,200 meters thick in some areas.

· In the United States, glaciers cover over 75,000 square kilometers, with most of the glaciers located in Alaska.

· During the last Ice Age, glaciers covered 32% of the total land area.

· If all land ice melted, sea level would rise approximately 70 meters worldwide.

· The land underneath parts of the West Antarctic Ice Sheet may be up to 2.5 kilometers below sea level, due to the weight of the ice.

· North America's longest glacier is the Bering Glacier in Alaska, measuring 204 kilometers long.

· Glacial ice often appears blue when it has become very dense. Years of compression gradually make the ice denser over time, forcing out the tiny air pockets between crystals. When glacier ice becomes extremely dense, the ice absorbs all other colors in the spectrum and reflects primarily blue, which is what we see. When glacier ice is white, that usually means that there are many tiny air bubbles still in the ice.

· The Kutiah Glacier in Pakistan holds the record for the fastest glacial surge. In 1953, it raced more than 12 kilometers in three months, averaging about 112 meters per day.

· In Washington State alone, glaciers provide 470 billion gallons of water each summer.

· Antarctic ice shelves may calve icebergs that are over 80 kilometers long.

· Almost 90% of an iceberg is below water--only about 10% shows above water.

· The Antarctic ice sheet has been in existence for at least 40 million years.

· From the 17th century to the late 19th century, the world experienced a "Little Ice Age," when temperatures were consistently cool enough for significant glacier advances.

How are glaciers relevant to our lives?

Glacial ice can range in age from several thousands to millions of years, making it valuable for climate research. To see a long-term climate record, an ice core is drilled and extracted from the glacier. Ice cores have been taken from around the world, including Peru, Canada, Greenland, Antarctica, Europe, and Asia. These cores are continuous records providing scientists with information regarding past climate. Scientists analyze various components of cores, particularly trapped air bubbles, which reveal past atmospheric composition, temperature variations, and types of vegetation. Glaciers literally preserve bits of atmosphere from thousands of years ago in these tiny air bubbles. This is how scientists know that there have been several Ice Ages. Past eras can be reconstructed, showing how and why climate changed, and how it might change in the future.

Scientists are also finding that glaciers reveal clues about global warming. How much does our atmosphere naturally warm up between Ice Ages? How does human activity affect climate? Because glaciers are so sensitive to temperature fluctuations accompanying climate change, direct glacier observation may help answer these questions. Since the early twentieth century, with few exceptions, glaciers around the world have been retreating at unprecedented rates. Some scientists attribute this massive glacial retreat to the Industrial Revolution, which began around 1760. In fact, some ice caps, glaciers and even an ice shelf have disappeared altogether in this century. Many more are retreating so rapidly that they may vanish within a matter of decades. Scientists are discovering that production of electricity, along with coal and petroleum use in industry, affects our environment in ways we did not understand before. Within the past 200 years or so, human activity has increased the amount of carbon dioxide and other greenhouse gases released into the atmosphere.

The 1991 discovery of the 5,000 year-old "ice man," preserved in a glacier in the European Alps, fascinated the world (see National Geographic, June 1 1993, volume 183, number 6, for an article titled "Ice Man" by David Roberts). Tragically, this also means that this glacier is retreating farther now than it has in 5,000 years, and no doubt other glaciers are as well. Scientists, still trying to piece together all of the data they are collecting, want to find out whether human-induced global warming is tipping the delicate balance of the world's glaciers.

Note: The information as cited above was taken from http://www.nsidc.org/glaciers web address.

Glacial Morphology
(see also http://gemini.oscs.montana.edu/~geol445/hyperglac/glaciers101.htm )

Cirque Glacier: a small glacier occupying a cirque, but that does not extend down-valley from the cirque.

Valley Glacier: a valley flowing glacier. These glaciers may be the combination of several smaller glaciers joining and flowing together down a large valley.

Col

Cirque

Cirque: a semicircular or amphitheater-shaped bedrock feature created as glaciers scour back into the mountain.

Col: a low spot, pass, or ‘saddle’ along a cirque or an arête.

Arête

Arête: a steep-sided, sharp-edged bedrock ridge formed by two glaciers eroding away on opposite sides of the ridge.

Hanging Valley

U.S. National Park Service photo by N. King Huber, U.S. Geological Survey

Hanging Valley: a valley eroded by a small tributary glacier, joining the valley carved by a larger glacier. Its size and the type of parent rock over which it is moving determine the erosive capability of a glacier.

Headwall

Horn

Horn: a pyramid-shaped mountain peak created by several glaciers carving away different aspects of a mountain.

Headwall: the steep, cliffy back-wall of a cirque.

Tarn

Tarn: a lake found at the bottom of the concave glacial scour, generally located in the floor of a cirque.

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U-Shaped Valley: a glacially eroded valley.

Moraine

Moraine: an accumulation of unconsolidated material deposited by glaciers. These accumulations tend to be unsorted, angular debris.

End Moraine: an accumulation of unconsolidated material deposited at the terminal end of a glacier. The terminal moraine marks the farthest extent of glacial advance and thus is the end moraine located at the lowest elevation. These landforms are key in the formation of many range front lakes such as Jenny Lake along the Teton Range of Wyoming. Recessional moraines form as glaciers pause during periods of retreat, and thus are located at higher elevations than terminal moraines.

Photo by Michael A. Stecker.

Lateral Moraine: unconsolidated material deposited along the sides of an alpine glacier. As glaciers recede, these deposits may become ridges running parallel to the preexisting glacial advance.

Medial Moraine: A moraine formed when two glaciers flow together, combing their lateral moraines to form a ridge in the middle and on top of the glacier.

Crevasse: cracks in the glacial ice that from due to tension and stress initiated by frictional forces, changes in slope, etc.

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Ice Fall

Ice Fall: Generally found in steeper sections of the glacier – pieces of ice will break and fall from above, sometimes reforming to lower ice after coming to rest.

Exercise, Part 1

Click on the link below to begin your assignment. Each section will provide you with topographic maps and pictures of the glacial features you are to identify. Do not attempt to print information from the link. Start a new Word document, place your answers in it, and hand it in the following week.

http://www.uwsp.edu/geo/faculty/lemke/alpine_glacial_glossary/exercise/exercise.html

The link above is in no way claimed, contributed to, or maintained by Montana State University. It belongs to, and was created by the University of Wisconsin – Stevens’ Point - Geography/Geology Department.

Part 2: Continental Glaciation

10. Name the current ice sheets that exist on Earth and describe their location relative to the North and South Poles.

11. Give the location of the SEVERAL ice sheets that existed during the Last Glacial Maximum, about 18,000 years ago, but have since disappeared. You may need to do some research for this one.

12. Click on this link to see a recreation of melting of the Laurentide Ice Sheet. Notice how quickly the ice sheet melted between 11,500 and 8,400 years ago shrinking 80% in size during this time. What do you think is responsible for this rapid period of melting? Explain.

13. Click on this link to see the drainage patterns of North America from two million years ago and present. Notice that two million years ago Yellowstone drained into the Hudson Bay, why has this changed? Explain.

14. Look at the map titled “Late Wisconsinan and Holocene Retreat of the Laurentide Ice Sheet” provided in class. Find Long Island and Cap Cod off the coast of present day Connecticut and Massachusetts. Why do these posh and populous destinations exist and what are they made of?

Extra Credit: The Spokane Floods

Use the internet and the map titled “Glacial Lake Missoula and the Channeled Scabland” provided in class to describe to describe some of the most amazing events in recent earth history. In a paragraph explain how Glacial Lake Missoula was created, the mechanism for triggering the Spokane Floods, the size or magnitude of the floods, and some of the scientific evidence supporting the outburst flood theory

And the best thing about studying glaciers…

….is the view.