Book excerpt: This book explains to the hillwalker, in easy to understand but accurate terms, how geology has shaped the landscape of Snowdonia. A selection of thirteen guided walks are used to illustrate this in terms of what can be seen on the ground. Divided into two parts, it is intended to help those who love Snowdonia's mountain scenery to understand how this haunting landscape came about. The first half narrates the story of colliding continents, volcanoes, mountain-building and glaciation in creating Snowdonia, explaining why volcanoes occurred, the rocks they created and how to interpret signs of mountain-building and glaciation on the ground. The second half describes several recommended walks, of differing levels of difficulty, but all with a wide variety of geological features to be seen and, most important, enjoying consistently fantastic views of the very best of Snowdonia's wonderful scenery. The author has concentrated on what you can see as you walk around the hills, pointing to conspicuous, easily seen features in rocks and the overall shape of the terrain in accounting for the present day landscape.