Yellowstone has been a national park since 1872, but it was only in the 1960s that scientists realized the scale of the volcano - it's 44 miles across - and not until the 1980s did they grasp that this thing is fully alive and still threatens to erupt catastrophically. Yellowstone is capable of eruptions thousands of times more violent than the Mount St. Helens eruption of 1980. The northern Rockies would be buried in multiple feet of ash. Ash would rain on almost everyone in the United States. It'd be a bad day. Thus geologists are eager to understand what, exactly, is happening below all those volcano-fueled hot springs and geysers.