Wednesday was the annual test of Alaska’s tsunami warning system — but Homer, Kenai, Ketchikan, Kodiak, Sitka and Unalaska didn't hear it at all.

Midway along the 92-mile road that winds through Denali National Park, at a spot with an elevation of 3,500 feet and spectacular views of the Alaska Range and the braided rivers that flow out of it, an unstable wall of rock, ice, soil and clay rises precariously. The slope into which the road was cut eight decades ago is already collapsing gradually — and there are fears that it could collapse much more suddenly in the future.

A powerful wave as tall as 55-storey building crashed through a fjord in Alaska in 2015, stripping the mountainsides of trees and dirt. It was triggered by a landslide — and researchers say such tsunamis could pose an increasing risk in places like Western Canada as climate change melts glaciers.