2.5-mile out and back hike to the top of a flat-topped volcano and down into a series of canyon-like fissures, measuring from 20 to 50 foot deep and only a few feet wide. The fissures were created when Black Point erupted about 13,000 years ago when it was still beneath the waters of a much deeper Mono Lake. When the cinder and lava cooled and hardened under water, the top split open to form several hundred-yard-long cracks, or canyon-like fissures. When the waters of Mono Lake receded after the Ice Age, Black Point became a peninsula. It is the only fully exposed underwater volcano on earth.