The second-highest tsunami ever recorded struck Alaska in August last year, but almost no one noticed.
A landslide from a glacier dropped over a hundred million tons of rock into Tracy Arm fjord, pushing a 1,580-foot wave up the narrow waterway; it is a tourist hotspot, but the 5am strike time meant no cruise ships were nearby.
Traditional tsunami warnings would be useless, since the wave followed the landslide by seconds rather than hours, but scientists said better monitoring of glaciers could detect high-risk areas before the collapse.
Similar events have killed people in Norway and Greenland, and as climate change melts glaciers, Arctic countries face growing risks of landslide tsunamis causing disasters.