Dome

Overall view of the Old Faithful basin from hillside Observation Point (250 ft. above); The geothermal areas of Yellowstone include several geyser basins in Yellowstone National Park as well as other geothermal features such as hot springs, mud pots, and fumaroles. The number of thermal features in Yellowstone is estimated at 10,000. South of Norris along the rim of the caldera is the Upper Geyser Basin which has 410 geysers including Old Faithful, a cone geyser. Old Faithful was named in 1870 during the Washburn-Langford-Doane Expedition and was the first geyser in the park to receive a name. It is one of the most predictable geographical features on Earth, erupting every 35 to 120 minutes. Source: Wikipedia; http://en.wikipedia.org/wiki/Main_Page (accessed 9/6/2015)