Explore the steep cliffs of the Berwickshire Coast around Fast Castle. These are steeply tilted and folded rock layers, originally deposited as sand and mud on the floor of the Iapetus Ocean.

THE ROCKS: This is the best place on the east coast to see the rocks of the Southern Uplands. Layers of greywacke sandstone, originally formed on the floor of the Iapetus Ocean, have been crumpled in complex folds during the Caledonian Orogeny as the Iapetus Ocean closed. By examining these rocks in conjunction with the younger, undisturbed sedimentary rocks at Pease Bay, we get before and after snapshots of Scotland’s most important geological event – and we can see why James Hutton chose this area to search for the unconformity that he found at Siccar Point.

THE WALK: This is short but strenuous walk on rough paths, grassy slopes and bouldery beach. We’ll start with a quick visit to Pease Bay, which is a great contrast to the older rock and more rugged terrain to the south. Moving on by car to Dowlaw Farm, we descend to Fast Castle and then follow a rough path along the cliff tops to the shore at Dowlaw Dean, where we cut inland and complete a circuit back to the farm. I have classified this as an adventurous walk: involving walking along rocky beaches, clambering over rocks and steep climbs. Footwear with a good tread is essential, as there are places where a simple slip would be fatal. Distance 6km, duration 5 hours.

MEETING POINT & ROUTE: At the car park at the entrance to Pease Bay Caravan Park. From the roundabout on the A1, 4 km south of Torness Power Station, turn east on to the minor road signposted for Cove and Pease Bay. Follow this road past Cove, and down the hill to the caravan site. Park outside the main gates, in the car park on the right hand side.

Grid reference: NT794706 | Nearest Postcode: TD13 5YS | What3Words: spans.applause.taller | Route Map. After visiting Pease Bay we’ll drive a few km southeast on the A1107 and take a minor road to a car park beside Dowlaw Farm, NT855702.