Subsequent to the rise of Lassen Peak, several dacitic pumice cones developed in a rift extending northwest from the base of Lassen Peak. Then about 1,100 years ago several dacitic domes, the Chaos Crags, protruded through these cones and obliterated all but half of the southernmost cone. At least 300 years ago a series of large avalanches, possibly triggered by steam explosions, occurred on the north side of the Crags. These avalanches created their own 'air cushions' that helped accelerate them to speeds exceeding and push them partway up Table Mountain. The resulting wilderness of debris, the Chaos Jumbles, covers an area of . Manzanita Lake was formed as a result of Manzanita Creek being dammed by the debris. Steam rose from the domes of Chaos Crags until 1857.