Doublet Pools, in the Upper Geyser Basin near Old Faithful, exhibit distinct raised edges as a result of many years of mineral deposition. At intervals of about twenty minutes, the pools will beat like a drum, with the water surface visibly vibrating and accompanied by a audible thumping noise and ground vibration surrounding the pools, as a result of collapsing steam bubbles far below.
Steam rises from Doublet Pool. Upper Geyser Basin, Yellowstone National Park, Wyoming, USA