Sometime in the next 10-20,000 years, part of Hawai`i Island may crack with a quake and slide away, creating a 100' tsunami that could reach Honolulu in under 30 minutes.
We know this from the research of vulcanologists and earthquake watchers, and now you can see the results in a video simulation (via National Geographic).
Yet, it could also get smaller...in a landslide like the one depicted in this video.
There is some evidence that such a landslide created the Lihu`e Basin on Kaua`i.
Either way, the big earthquakes here last week remind us of a larger sort of sustainability issue for these islands...how to maintain a civilization on shifting plates and magma.