Photo #21434 - Access to Mammoth Hot Springs Upper Terraces Thermal Area View from walkway of Mammoth Springs Upper Terrace. Several key ingredients combine to make the Mammoth Hot Springs Terraces: heat, water, limestone, and a rock fracture system through which hot water can reach the earth's surface. Today's geothermal activity is a link to past volcanism. A partially molten magma chamber, remnant of a cataclysmic volcanic explosion 600,000 years ago in central Yellowstone, supplies one of the ingredients, heat. 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.