This is the way that many of the bubbling mud areas looked 35 years ago when I was last here. I am not sure where this was in the park. The only one I saw this trip was about the size of the average hot tub. This area is much bigger than that. Most of them seem to be dry cracked mud now. I also noticed that there appear to be fewer hot springs.

The "activity" of the hydrothermal features varies ... the changes are caused by the many earthquakes, most of which are unnoticed by park visitors. There were approx. 311 earthquakes in the Yellowstone area in February 2007 alone. One must remember that the Yellowstone Caldera is the site of a potential super volcano. It is one of the most unstable areas in the world.