Chaos Crags

The Chaos Crags are among the most noteworthy landmarks in the park. The pinkish lava domes known as the Crags are remnants of a series of 5 volcanoes which erupted about 1100 years ago, in approximately 900 AD. They are possibly the steepest volcanic domes anywhere.

The Chaos Jumbles is a vast rockfield which lies at the feet of the Chaos Crags. It resulted from the collapse of one of the Crags in 1670, when a giant mass of lava broke away from the north side of the Crags. Molten rock beneath one of the Crags reached close enough to the surface to superheat the ground water, producing a steam explosion that triggered one or more rockfall avalanches. This triggered a sizeable rockslide which rode a slick base of wet volcanic ash.

The avalanche resulting from the collapse of the Crag, possibly as a result of a volcanic explosion. It reached speeds of 100 to 200 miles per hour and carried 200 million cubic yards of debris. The debris reached Manzanita Creek, creating a dam, and producing Manzanita and Reflection Lakes.

The rockslide crossed 2 miles of flat land and reached all the way up the side of Table Mountain, shown below. The moonscape of rocky debris covers a full 2 square miles.

The Chaos Crags were referred to on an 1864 map as the "North Peak" of "Lassen Butte." The Crags themselves lack summit craters, as exist on Lassen and other peaks.

The danger of a modern day rockfall from Chaos Crags has been in the past considered significant. After a 1974 report, a number of facilities in the vicinity of the Chaos Jumbles area, including the visitor center, museum, and guest lodge at Manzanita Lake were closed, although some of these facilities were later reopened.