Words to Know
White areas show current glacial coverage
Used with permission from USGS
Nearly three million years ago, a period called the "Ice Age" began. During this long period, the temperatures on the earth were much colder than they are today. Each year much more snow fell than melted, so a snowfield began to accumulate. As the weight of the snow increased, the lower layers turned into ice. With even more weight, these lower layers of ice began to flow and move very slowly. This is what we call a glacier.
Find out more about glaciers including their effects on the Vermont landscape at this website: http://www.uvm.edu/whale//GlaciersWhatAre.html.
Ice covered North America as far south as Pennsylvania and Missouri. The glacier was so thick that the highest mountains of New England were completely covered with ice.
When for many years more snow fell than melted, the glacier grew, or advanced. When more snow melted than fell, the glacier shrank, or retreated. During the ice age, the glacier advanced and retreated over Vermont four times. The most recent retreat was only about 10,000 years ago!
All this ice advancing and retreating over Vermont changed the landscape dramatically. The ice blocked the flow of water so that large lakes were formed on the eastern and western sides of the state. At one time, the water on the western side of the state, now Lake Champlain, was salt water. Geologists gave this glacial lake the name Lake Vermont. People have found fossils and bones that tell us that there were sea animals living in the glacial lake.
Get a timeline on the formation of Lake Champlain at this website - http://www.lcmm.org/site/harbor/resource_pages/timeline/geological.htm
The huge glaciers dragged rocks and soil beneath them. These rocks were frozen in the ice and ground against the earth's surface like giant pieces of sandpaper. Mountain peaks were smoothed down and steep valleys were widened. Often rocks were ground together into a fine dust called rock flour. In many areas the soil was greatly compressed to form clay.
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