Some 8000 to 9000 years ago, in the early Holocene Age, a huge rockslide in Köfels formed the high Alpine plateau of Niederthai and the Stuiben Waterfalls. Probably it was the Alps' biggest crystalline rockslide ever. This natural catastrophe can be compared to an 7.5 earthquake on the Richter Scale. About 2-3 km³ of sliding rock masses were spread over an area of approximately 12 km².
The giant rockslide, today known as "Tauferberg", blocked the whole Ötztal Valley and the Ötztaler Ache Brook on a total length of 3 km. Therefore a big lake was formed at the height of Längenfeld and the basin of Längenfeld was built. In the course of time, the water masses decreased and broke through the Maurach Ravine, close to today's federal road.
On the opposite part of the valley the huge rocks blocked the natural drain of the Horlachbach Brook. In Niederthai a lake district was formed by the waters, which developed into the giant Stuiben Falls, Tirol's biggest waterfall with a falling height of 159 meters.
Still today, geology experts are not sure about the reason of this huge rockslide. Weather conditions, earthquakes or volcanism? A quite interesting theory of the British scientists Alan Bond and Mark Hempsell centers on a comet's impact. The flight path of a celestial body - noticed by an ancient Sumerian astrologist - was visible far beyond the European borders: the "Nineveh clay tablet" is widely known and much discussed among experts.