Big Southern Butte is the largest and youngest (300,000 years old) of three rhyolitic domes formed over a million years near the center of the Eastern Snake River Plain in the U.S. state of Idaho. In fact, it is one of the largest volcanic domes on earth. It rises approximately 2500 vertical feet (762 m) above the lava plain in southern Butte County, east of Craters of the Moon National Monument.