buried by volcanic lava flows from nearby Mauna Kea and Mauna Loa. However, based on a sharp increase of incline on the submarine slope of the volcano at a depth of , scientists estimate that in its prime the portion of Kohala that was above the water was more than wide. Geologists estimate that the volcano was once about twice its current size. The volcano is so old that it experienced, and recorded, a reversal of magnetic polarity (a change in the orientation of Earth's magnetic field so that the positions of the North and South poles interchange) that happened 780,000 years ago. Fifty flow units in the top of exposed strata in the Pololu section are of normal polarity, indicating that they were deposited within the last 780,000 years. Radiometric dating ranged mostly from 450,000 to 320,000 years ago, although several pieces strayed lower; this indicated a period of eruptive history at the time. Kohala was devastated by a massive landslide between 250,000 and 300,000 years before present. Debris from the slide was found on the ocean floor up to away from the volcano. Twenty kilometers wide at the shoreline, the landslide cut back to the summit of the volcano, and is partially, if not largely, responsible for the volcano losing in height since then. The famous sea cliffs of the windward Kohala shoreline stand as evidence of the massive geologic disaster, and mark the topmost part of the debris from this ancient landslide. There are also several other unique features found on the volcano, all marks made by the decimating collapse. Kohala is thought to have last erupted 120,000 years ago. However, several samples of a more recent date have been obtained. Two samples collected about apart, obtained from Waipio Valley on the volcano's east flank in 1977, were dated reliably to 60,000 years. Another double set of samples, collected from the western part in 1996, was measured to be 80,000 years in age. The samples have been treated with skepticism by the scientific community, and their ages have been directly challenged. The rocks collected from the west site have not been tested by subsequent experiments. The lava samples collected from the eastern site were allegedly found under a Mauna Loa lava flow, which had been previously dated to 187,000 years. The Kohala lava flows could be as young as 120,000 years although they may be even younger.