The Hitchhikers Guide to the Galaxy ascribes the pleasing depth and drama of Earth's fjords to an alien planetary engineer named Slartibartfast. A model produced by Mark Kessler at the University of Colorado in Boulder and his colleagues captures a more plausible sculptural process involving only ice and mountain ranges. The researchers show that a tendency for ice to flow through existing mountain passes deepens these passes, reinforcing the original tendency. This feedback can lead to the carving of kilometre-deep fjords in a million years.
Their model also suggests that once a landscape is equipped with fjords its ice caps will be smaller and more sensitive to climate change, as it is easier for the ice to get away.