The Lituya Bay AK rock slide and tsunami of 1958 is a worst-cast example of what could happen. I've read that there are several risk areas in Prince William Sound AK that are vulnerable for big slides and a potential repeat.
https://en.wikipedia.org/wiki/1958_Lituya_Bay,_Alaska_earthquake_and_megatsunami
When they did a modern survey of the bottom of Douglas Channel a few years ago, they discovered an unknown fault line and two nearby submarine landslides of the same size as the Lituya Bay slide at over 30 million square metres each.
Granted, these were underwater, but also moved a lot of water.
When the local First Nations, the Haisla, came to this area there was nothing but scrub brush for 1.5 kilometres inland from the head of Douglas Channel.
They met the Kitsumkalum people from the Skeena Valley because the Haisla saw strips of cedar bark floating down the Kitimat River, so went upstream to meet them...this tells me this happened well after the glaciers left and there were mature trees on the valley floor.
Why scrub brush 1.5 kilometres in from the high tide line? Why was the place not inhabited because the Kitimat River had big salmon and oolichan runs? Tsunami?
Douglas Channel, the Kitimat Valley, and Kitsumkalum Valley all link together through the Coast Mountains. It takes a lot of effort to clear a path through a mountain range.
There are six hot springs, all on the eastern margin, and Canada's youngest volcano is at its northern end.
Really big stuff happens on this whole coast...it's just that it happens on geologic timescales and not so much during the recent past when things were written down.
Then there's that Canary Island volcano with a 25 kilometre slope threatening to slide which faces North America's east coast...
