Glaciers: Movers & Shapers

Glaciers are large masses of moving ice that are often called rivers of ice. They form slowly and some take over 100 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. The rate of glacial movement can be slow or glaciers may move several hundreds of feet in a season resulting in a glacial surge.

Glaciers are heard cracking and grinding as they move. Photographs of a glacier taken over a period of time show the rate of its advance or retreat. As glaciers 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 as they move.

Glaciers are usually found at higher elevations and latitudes. They are found in 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. These glacial melts can endanger the environment, wildlife, people, and property. Changes in Mt. Rainier glaciers in Washington state illustrate how glaciers can be hazards. 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.

Several glacial studies research projects have examined glacial change. Scientists have mapped the locations of the world’s glaciers and monitored glacial changes to better understand climate change and global warming. Scientists drill and extract ice core samples from glaciers around the world. These samples suggest that the concentrations of greenhouse gases such as carbon dioxide and methane are increasing in the atmosphere. The burning of fossil fuels and deforestation contribute to these increases and could cause possible global warming. Some scientists have predicted that global warming will melt glaciers, resulting in a global sea level rise of disastrous proportions.

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.