The Great Rift is a 52-mile (84 kilometer) long system of fissures along which a chain of volcanoes erupted. Crescent Butte is the oldest of these cinder cones, created during the earliest eruptions here about 15,000 years ago. North Crater and Big Craters' cones were formed by the most recent eruptions about 2,000 years ago. The seven mile loop road provides access to all of these features.