How can the ground in Alaska become unstable?

There are two reasons for this. Firstly, Alaska is in an area that has earthquakes and secondly during summer months melting permafrost (frozen sub-soil), forms marshland, known as 'muskeg' which makes buildings and roads unstable.

In Alaska, degrading permafrost, steep slopes, heavy rain, retreating glaciers, ground-shaking from earthquakes, and isostatic rebound are important mechanisms that can trigger devastating landslides.