Rex Trulove
The title of this picture, the edge of the beach, might seem strange. The altitude here is roughly 4,000 feet above the valley floor, after all. However, the name is accurate. You see, at the end of the last ice age, this whole valley was a vast lake. The plaques in this image are literally where the shore of that lake was.
All of the previous pictures were taken from locations that would have been under the surface of that lake.
What can’t be seen in any of these pictures is that the lake reached beyond Missoula, Montana, which is about 45 miles south of this view, behind me when this image was taken. The lake had a total area of over 3,000 square miles and held more than 500 cubic miles of water. Ice dammed the water up to the northwest and the ice dam occasionally ruptured, spilling huge amounts of water, ice, and sediment that drained away across northern Idaho, eastern Washington, and down the Columbia River Gorge.
This was the largest ice-dammed lake known. It is also the reason the Mission Valley is so fertile, though it is also littered with rocks that were transported there by the enormous glaciers of the ice age.
Through this entire area, there are many visible signs of the glaciers and of Lake Missoula.
It is rather sobering to realize that 10-15 thousand years ago, this view would have been of one giant lake, with only islands visible above the water. In fact, I would have been standing on one of those islands to take this picture.
