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The birth of a glacier

What does it take to grow a glacier?

spacer image Growing a glacier requires two essential ingredients: adequate snow fall and a cool climate. In warm climates, high mountain peaks may recieve heavy snowfall in the winter, only to have it melt away during the warm summer months. A cool climate means cool summers. In a cool climate, some winter snow may survive each year, providing a base for the next year’s snow. Glaciers can grow only when the amount of snow that accumulates is greater than the amount that melts each year. Heavy winter snowfall and cool summer temperatures both favor the growth of glaciers.
Bird’s eye view  glaciers
This image was taken in Summer near Glacier Bay National Park in Alaska. You can easily see that snow at lower elevations has mostly melted, while snow near the peaks persists. Only at high elevations can we find the right conditions for glacier growth. Click on image to see at full size.

If conditions are right...

spacer image Over many years, perhaps a few centuries, layer upon layer of snow builds up. As the mass thickens the weight of the snow presses down, forcing the snow at the base of the glacier to recrystallize into dense glacial ice. Eventually, when the ice reaches a thickness of about 100 feet, the ice begins to squeeze outward and move under the pressure of its own weight. Once the ice starts to flow, it’s no longer just a thick lump of ice-a glacier is born!
spacer image As the glacier flows downhill, it descends to warmer zones where the snow melts from year to year. The boundary where snow melting equals snow accumulation is called the annual snowline. The snowline varies from year to year depending upon the amount of snowfall (precipitation) and temperature.

More on glacier growth
| Return to glacier index |

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This page was last updated on 5/10/99