West Thumb, Yellowstone National Park, Wyoming, September 12, 2007.
The West Thumb Geyser Basin 44°25′07″N 110°34′23″W, including Potts Basin to the north, is the largest geyser basin on the shores of Yellowstone Lake. The heat source of the thermal features in this location is thought to be relatively close to the surface, only 10,000 feet (3,000 m) down. West Thumb is about the same size as another famous volcanic caldera, Crater Lake in Oregon, but much smaller than the great Yellowstone Caldera which last erupted about 640,000 years ago. It is interesting to note that West Thumb is a caldera within a caldera. (Wikipedia)
The image above was used in my video slideshow, Yellowstone Lake Vicinity, below:
Random travel image #33