August 10, 2001
This photograph of Mendenhall Glacier, in southeast Alaska (near Juneau), was taken at the end of June from the Mendenhall Glacier Visitors Center. Mendenhall Glacier is approximately 12 miles long and 1 1/2 miles wide (at its widest point). This glacier is fed by the 1,500 square mile Juneau Icefield. When the dirty ice in the foreground, which results from melting and ablation processes, reaches the water, huge hunks of ice may calve into the Lynn Canal (not a manmade canal). When this happens, fresh, blue ice is revealed.
As sunlight travels into snow or ice, the ice grains scatter a large portion of it. If the light is scattered by a few inches of snow, for example, the snow will still appear basically white. However, because slightly more red and yellow light is absorbed by the grains compared to blue light, if the snow or ice is sufficiently thick (generally, more than 2 feet thick), the light emerging from the snow or ice layer consist of more blue photons than red photons.