A Wrinkle in the Skin — John Christopher

A massive series of powerful earthquakes on a worldwide scale reduce towns and cities to rubble and plunge the survivors into barbarism. Most of western Europe is dramatically uplifted, transforming the English Channel into a muddy desert, while elsewhere lands are plunged below sea level and flooded.

Matthew Cotter, a Guernsey horticulturalist, finds himself one of only a handful of survivors on the former island. Cotter decides to trek across the empty seabed to England, in the faint hope that his daughter has somehow survived.