The Pali Lookout, Hwy 61, view is looking north along the Ko'olau Mountain.

Ko'olau Mountain forms the eastern coast of Oahu and is not technically a mountain, but the western ridge of a massive volcanic caldera which at one time rose to over 10,000 feet, three times its present height. The eastern side of the crater disintegrated and slid into the Pacific Ocean during one of the volcano's numerous eruptions in prehistoric times. The western lip of the crater and Kaneohe Bay are all that remain of the caldera. Some geologists date the most recent eruption at 32,000 years ago and believe that it could erupt again.