Glaciers

This river of ice flows slowly as it makes its way to the sea.

In the Juneau area, there are about thirty glaciers, huge rivers of solid ice that flow about one to ten feet per day. They stretch over 15,000 square miles. How quickly a glacier moves is dependent on three main factors—temperature, thickness of the ice, and the slope of the land. As the glaciers flow, they displace soil, rocks, and other debris. Once a glacier reaches the open water of the ocean, calving occurs. This is when huge ice chunks break off and fall into the sea creating icebergs, which can spend years floating about before finally melting.

Glaciers form from falling snow, which gets packed down into huge rivers of ice. They comprise 10% of the earth’s surface. When they flow, they do so as a unit. Glaciers move when an accumulation of ice is about 200 feet thick. Glaciers can be as small as a car or as large as a small country. As they move, glaciers carve out the land. Such is the case with the Great Lakes, which were formed during the last Ice Age as glaciers slowly gouged the earth.

Glaciers are of great importance. They contribute huge volumes of freshwater to both land and maritime environments. The glaciers in Southeastern Canada discharge almost twice as much freshwater as the Mississippi River. In addition, their steady movement grinds mountains in fine particles providing essential nutrients that form the basis of the food web: nitrogen, phosphorus, and organic carbon.

One of the largest glaciers in Juneau is the Mendenhall. Scientists have studied it continuously since 1948. While some glaciers in the Juneau area are advancing, most, like the Mendenhall Glacier, are receding. Over the past many years this glacier has receded two miles. Other glaciers that are receding are doing so at the rate of about two feet per day.

Human activity is greatly impacting the glaciers. Global warming is a serious problem—so much so that scientists predict that within 100 years, glacier ice melt with cause the oceans to rise dramatically, perhaps as much as 20 feet. Of course, this means that all coastal areas will be flooded. Will this affect where you live?

This glacier is massive. I saw a black bear sitting nearby and it looked like the head of a pin in comparison to the huge glacier.

Here you see the glacier calving. This is when huge chunks break off and fall into the sea.

This glacier is black. As it moved, it picked up dirt, rocks, and other debris.

The Margerie Glacier