the phenomenon is named after the val piora or piora valley in switzerland, where it was first detected; some of the most dramatic evidence of the piora oscillation comes from the region of the alps. glaciers advanced in the alps, apparently for the first time since the holocene climatic optimum; the alpine tree line dropped by 100 meters. in the middle east, the surface of the dead sea rose nearly 100 meters (300 feet), then receded to a more usual level. a few commentators have associated the climate changes of this period with the end of the uruk period, as a dark age associated with the floods of the gilgamesh epic and noah's flood of the book of genesis.