P. M. Allen & Audrey A. Jackson, Classical Areas of British Geology: British Geological Survey, SB, 94 pages, Her Majesty's Stationery Office, 1985.

The walks described in this guide pass through some of the most beautiful scenery in the Snowdonia National Park. The walker will recongise the influence of geology on the scenery: from the coastal plain of sand dunes and alluvium concealing Tertiary rocks to the craggy peaks of the Rhinogs sculpted from some of the oldest fossiliferous rocks in Britain. At Rhobell Fawr, basaltic lavas may be seen which are the earliest signs of the 'ring of fire', a widespread volcanic episode which affects much of North Wales. Ice-scoured cwms, precariously perched erratics and wide tracts of till are evidence of the Pleistocene glaciation. The well known Dolgellau Gold Belt crosses the area and many other minerals have been extracted; the walker will pass many trials and ruins of the old mines.