Photo #21403 - Roaring Mountain Hot Springs - Roadside turnoutwith scenic view area Paved turnout, both sides of highway. Roaring Mountain is a large, acidic thermal area (solfatara) that contains many steam vents (fumaroles). In the late 1800s and early 1900s, the number, size, and power of the fumaroles was much greater than today. YELLOWSTONE NATIONAL PARK - Madison to Mammoth Hot Springs - Montana / Wyoming State Line With half of the earth’s geothermal features, Yellowstone holds the planet’s most diverse and intact collection of geysers, hot springs, mudpots, and fumaroles. Its more than 300 geysers make up two thirds of all those found on earth.