Snowdonia's Secret History

Standing on the summit of Snowdon — Yr Wyddfa in Welsh — you are on a jagged peak shaped not by volcanic fire or shifting tectonic plates, but by ice. The hollow below to your left is Glaslyn, a dark and still lake occupying a corrie: an armchair-shaped hollow carved by a rotating mass of glacier ice. The valley behind you is U-shaped — wide, flat-bottomed, and steep-sided, cut through solid rock not by any river but by a glacier hundreds of metres thick. Every feature of this landscape is a geological record of the last ice age, which ended around 10,000 years ago. It took roughly 100,000 years to carve.