[Island Chris]

Sure, underwater slides can cause tsunamis, including adding to the amplitude of one form a quake. But, if the slide is big enough, these can be giant ocean-crossing ones. For example, some think that a collapse of one of the Canary Islands caused marine deposits at up to 23 m elevation in Bermuda (which presumably is not uplifting, so had to be something like that if the global sea level was not much higher than today).

Working on my talk...at 4:45 AM, but am jet-lagged.

Chris