Black Sand Pool, Upper Geyser Basin, Yellowstone National Park
Detailed Description
Black Sand Pool, in Yellowstone National Park's Upper Geyser Basin. The hot spring is known for it's thumping behavior, which occurs every few minutes due to collapse of bubbles within the spring. The thumping is strong enough to be heard and felt by anyone nearby. USGS photo by Mike Poland, July 21, 2026.
Sources/Usage
Public Domain.