Lakeside disaster

Ancient tsunami devastated Lake Geneva shoreline 

I didn't know this:

 In ad 563, more than a century after the Romans gave up control of what is now Geneva, Switzerland, a deadly tsunami on Lake Geneva poured over the city walls. Originating from a rock fall where the River Rhône enters at the opposite end of the lake to Geneva, the tsunami destroyed surrounding villages, people and livestock, according to two known historical accounts.

It seems to have been caused by a rock fall, but not involving an earthquake.  How odd.