Abyss Pool -- West Thumb Geyser Basin
Abyss Pool is the deepest hot spring in Yellowstone, at 53 feet. It was named because this great depth makes it seem like the pool has no bottom... like an abyss...
The bright blue color indicates that the temperature of the water in this pool is very high. Runoff from the pool flows down towards the lake, and there are microbial mats and mineral deposits around its periphery.