Glaciers: Movers & Shapers


STUDENTS: Module 4: Forces in the Environment

Glaciers icon. Glaciers: Movers & Shapers Profiles the force of these rivers of ice and continental ice sheets as they sculpt valleys, create a variety of lakes and leave flattened fields behind.

Glaciers are large masses of moving ice that are often called rivers of ice. They Photo: Mt.Ranier.form slowly and some take hundreds and perhaps thousands of years to reach their maximum size. Glaciers form because the annual snowfall in an area does not melt completely in the summer, and accumulates over time. As the snow accumulates, it slowly compresses under its own weight into a huge mass of ice. When a glacier’s size reaches about 18 meters thick, its weight and the pull of gravity cause it to move slowly over land changing the land’s surface features. Valley glaciers are found on land that slopes and flow downhill, while continental glaciers are on flat land and move out from their edges.
Glaciers either retreat or advance depending upon the amount of snow accumulation and melting.

Photo: CrevasseThe rate of glacial movement can be slow or glaciers may move several hundreds of feet in a season resulting in a glacial surge. Photographs of a glacier taken over a period of time show the rate of its advance or retreat.

Glaciers are heard cracking and grinding as they move. They pick up rocks and debris underneath them and carry them along, eroding the landscape. Glaciers can either wear down the earth’s surface or build up new landforms by depositing debris.
Glaciers are usually found at higher elevations and latitudes. They are found in Photo: Greg stands in view of the mountain.mountainous areas, on islands, near the equator, and along some coastlines. Glaciers can become natural hazards if they melt during the warmer season and cause flooding in surrounding areas. Glaciers cut into headwalls and valley walls making the slopes unstable, often resulting in rockslides. On unusually hot or rainy days, cavities within the glacier may suddenly release water, causing glacial outburst floods. Outburst floods often roar rapidly along carrying rocks and debris (debris flow) and may suddenly and without warning cause a rapid rise in water level in the valley.

Tidal glaciers along coastlines can break off into icebergs during a process called calving. Often massive in size, icebergs can float into shipping channels and endanger ships. The U.S. Coast Guard has, since 1913, worked with the International Ice Patrol to monitor iceberg danger in the North Atlantic Ocean. The dangerous mix of icebergs, fog, severe storms, fishing vessels and busy trans-Atlantic shipping lanes could result in tragedy. The Titanic disaster in 1912, which resulted in 1517 deaths, and the loss of the S.S. Hanshedtoft in 1959 are proof of the danger of icebergs. Photo: Taking core samles of the ice.

Since 1974, scientists at the Vostok Station in Russia have examined ice core samples from Antarctica. Scientists have identified trapped bacteria, fungi, pollen grains, and algae that are almost 4,000 years old. Glaciers have also preserved fossil remains, such as those of whales, in the state of Maine. The 5,000-year-old “ice man” found in the Austrian/Italian Alps and a 550-year-old Canadian are providing information about human evolutionary and cultural history.

Throughout the history of the Earth glaciers have increased and decreased in size. Analyzing glacial changes helps us better understand the complex relationships between climate, the environment, and living things.
Photo: Man scaling crevasse.

Photo: Pots glazed with materials left by past glaciers.
crevasse
glacier
ice
debris
core
calving
iceberg
avalanche
erode



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