© Epoque
Its is a well-published and uncontroversial fact that in the recent prehistoric past a gargantuan rock shelf on the western shore of Lake Tahoe collapsed. FIVE SQUARE MILES of rock and sediment slipped into the gin-clear waters of the deep alpine lake and vomited a 300′ high tsunami wave that raced across the lake in five minutes, crashed on the eastern shore, ran up a 1000 feet high, and retreated leaving scars on the landscape visible today. The oscillating "seiche waves," rocked back and forth and in and out of the lake for half an hour of lacustrine hell.
Lake Tahoe was a bad place on a bad day.
When was the bad day? As determined in the most recent detailed study by James Moore et al. (2014) link below, the youngest estimate for the catastrophic event is our favorite geological and cultural milestone of 12,000 years ago, and the outer limit is 21,000. This range is supported by two sets of data. The older limit is defined by dating a glacial moraine no older than 21,000 years, which was breached by the debris flow. (If it happened today, and was studied thousands of years in the future, it would also be constrained by this early date).
Comment: The event was also witnessed from across the North Sea in Denmark and the Netherlands according to the American Meteor Society.