California’s Long Valley Caldera is one of the world’s biggest calderas, measuring 20 miles long by 11 miles broad and up to 3,000 feet deep. The Bishop tuff, a welded tuff that characterizes the area, was produced 760,000 years ago when a cataclysmic eruption ejected hot ash that eventually cooled and became the Bishop tuff.
Upon eruption, the ash went eight miles into the air, with deposits reaching as far east as Kansas.
Despite the potential for total disaster if Long Valley erupts, nothing is written about it. Instead, the focus is on Yellowstone, a supervolcano located hundreds of miles to the northeast.
Long Valley, though, may be on the verge of exploding, according to the Science Channel.