A two-legged tower

Crashing waves from the wide-open Atlantic Ocean continually carve the sandstone coast of Orkney, the small island chain just off Scotland's northern tip. The exposed striations here at Yesnaby, on the west edge of Orkney's main island, show how Devonian sediment layers were built up and compressed at odd, often zigzagging angles before being revealed by erosion. The effect is especially visible on Yesnaby Castle, the stilted sea stack at our photo's center. Rising about 115 feet, the crooked 'castle' is a popular target for intrepid climbers, despite its seemingly precarious posture on two legs.