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Studying Earth’s Ice
Every month during the summer, a ship carrying scientists and support staff arrives at a small research station on an island in Antarctica. This station is called Palmer Station. It is one of three stations that the United States has on Antarctica, which is Earth’s most southern continent. About 98 percent of the continent is covered by ice. It is the coldest, driest continent in the world.
Living in Antarctica is unlike life anywhere else. The station is so remote that all supplies arrive by ship, usually about once a month. Most of the scientists at the station study marine biology. They focus on the wildlife that live in the region, including penguins and elephant seals. The station also acts as a base for scientists who collect different kinds of data about how the ice is changing as Earth’s temperature warms.
People who live in Antarctica have to adjust to the cold and also the extreme days and nights. The sun shines for nearly 24 hours a day during the summer. And then, for a couple of weeks during the winter, there is no direct sunlight. The sun rises a few degrees above the horizon, but it stays behind a glacier, so the station remains in its shadow. A glacier is a flowing mass of ice and snow that forms on mountaintops and near the North and South poles.
The entire continent of Antarctica is made up of glaciers. Glaciers form when snow accumulates in the same area over many years. Each year, new layers of snow bury and compress the previous layers, similar to how layers of sediment compress over time to form sedimentary rock. Over many years, the snow becomes more compacted and denser until it turns into ice. Glaciers cover 15 million square kilometers of Earth’s land surface and hold ice that can be hundreds or hundreds of thousands of years old.
How Glaciers Move
Even though they are made of layers of solid ice, glaciers flow like powerful rivers. The weight of a glacier is what causes it to move. Weight is the gravitational force exerted on an object by a planet or moon. Gravity is the attractive force between all matter. Gravity is a result of an object’s mass. The more massive an object is, the more its gravity will pull on other objects. Non- scientists often think that an object’s weight is the same as its mass. The two are related because an object’s weight depends on its mass. However, weight also depends on the force of gravity. Here on Earth, weight is calculated by multiplying the object’s mass by the force of Earth’s gravity.
Glaciers are so massive that Earth’s gravity pulls down on the upper layers of ice, causing them to slowly move downward. This is possible because ice is softer than rock. The force of the glacier’s own weight deforms the ice so that it flows down mountains or spreads out across plains or the ocean.
At the same time as glaciers flow, they can also either expand or retreat. A glacier expands when winter snowfalls are greater than summer snowmelt. It retreats when winter snowfalls are less than summer snowmelt.
Most glaciers expand or retreat very slowly. It can take many years for there to be a significant change. However, sometimes glaciers retreat very quickly. For example, Muir Glacier in Alaska has retreated 12 kilometers (7 miles) in just 40 years. Ocean water now fills the valley where the glacier used to be.
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