However, in the light of the Mount St. Helens eruption of 1980 and from examination of the Mount Shasta deposits, it has become clear that the hummocks are a debris-avalanche deposit. Like these mountains, Galunggung has a horseshoe-shaped crater indicating a massive landslide, and examination of shattered lava blocks revealed them to be similar to deposits on the other two volcanoes. According to radiocarbon dating of samples taken from a lava flow, the landslide happened within the last 23,000 years.