We expected to see a few snowflakes on Banks Ridge in Baldwin last week, not a snowstorm accumulating 4 inches of white. For Hall, Habersham and Banks County that’s a considerable amount of snow. Isn’t it conceivable that some very long time ago, under the right conditions and with lots more snow, there could have been glaciers in North Georgia?
The answer is no. At least not in the past 300 million years, which is the time period for which we have a fairly good amount of geologic and climatic evidence. A strong piece of evidence for a past glacier is a U-shaped valley, or glacial trough. For example, there’s Going-to-the-Sun-Road at Glacier National Park in Montana. Traveling northeast, one sees St. Mary Lake on the right. To the left, the Rising Sun vacation camp comes into view. Just beyond that, in the northwest, there’s Rose Creek emerging from a magnificent valley that the creek couldn’t have shaped by itself. The slopes form a perfect rounded trough with their concave shapes, indicating that a glacier once moved through. Here in Georgia, valleys are V-shaped with no major change in slope angles from top bottom. That’s characteristic for the action of rivers.
Glaciers aren’t frozen rivers. They are massive accumulations of ice, resulting from snow piling up year after year and not melting away during summer. The process starts high up in mountain areas where the snow might find a niche that protects it from melting. Over time, the weight of the accumulating snow compresses the bottom layers into solid ice. As more weight is added at the highest part of the valley, the ice mass begins to slowly slide downhill. In the process, it loosens chunks of the least solid rock in the valley walls and drags them along. Now it has become the world’s largest but slowest bulldozer. The glacier grinds and plows its way down the valley at a speed of what can be just a few inches per month. Extreme cases are known, though. In 1937, Black Rapids Glacier in Alaska made the world record by moving 220 feet a day.
In the change to warmer climatic conditions, glaciers melt away (they don’t really “retreat”), leaving their U-shaped valleys behind. We don’t have any in Georgia. But still, Habersham’s V-shaped ones looked gorgeous covered in last week’s snow.
Rudi Kiefer, Ph.D., is a professor at Brenau University, teaching physical and health sciences on Brenau’s Georgia campuses and in China. His column appears Sundays and at gainesvilletimes.com.