OUTER HEBRIDES: LANDSCAPES IN STONE

The Outer Hebrides contain a huge range of contrasting and spectacular land- and seascapes. Lewis has a featureless peatland core bounded by dramatic sea cliffs; neighbouring Harris is rugged but fringed with stunning beaches; the Uists have gentle fertile machair. But the islands were all built from the most ancient rocks in Britain - Lewisian gneiss, about three billion years old. Alan McKirdy traces their extraordinary journey through time and across the globe.