The 1,700 foot wave in Alaska was from a landslide. The more famous earthquake one happened a few years later. From a reader:
The enormous 1958 Alaskan tsunami was caused by a landslide rather than by an earthquake. A landslide is the only thing that can cause a tsunami to be hundreds (or even more than a thousand) feet high. This is a very rare phenonenon. The Alaskan tsunami occurred in a remote bay, and was seen by only a few fishermen (some of whom miraculously survived). That’s the
scary thing about the volcano in the Canary Islands that has been mentioned
in the Corner lately — if the mountain collapsed into the ocean at once,
it would produce a huge wall of water that could wipe out much of the East
Coast of the United States. There is evidence that similar events have
happened in prehistoric times.
Earthquakes are a much more common cause of tsunamis. The resulting water
surge may not be nearly as high as that caused by landslides, but as we saw
in the past week it can be very deadly. And this was one big mother
earthquake.
Amazing what one can learn from The Discovery Channel.
You might be interested in Catastrophe, by David Keys, a fascinating
account of the far-reaching effects of a cataclysmic volcanic eruption in
535 A.D., in present-day Indonesia.