Location: Berwickshire

Map: OS Landranger 67 (GR780718)

Distance: 7 miles (11km)

Time: 3 hours 30 minutes

Terrain: signposted paths

How old is the Earth? In the late 18th century the accepted answer was a few thousand years. But after 30 years of studying every bit of exposed rock he came across, East Lothian farmer and chemist James Hutton was convinced the timescale was wrong.

It was clear to Hutton that a constant process of erosion and deposition was in operation, with the deposited materials then uplifted so that the whole process could start again. In the meantime, molten rock from the Earth's centre was constantly adding new rock to the process.

Hutton realised the land we stood on had already been recycled many times. He had found lots of evidence for his theories, but he needed something really obvious. He found this at Siccar Point in 1788. Here, vertical beds of grey sedimentary rock are clearly overlain by horizontal beds of red sedimentary rock. Hutton knew the vertical beds had been deposited horizontally, but could only guess at the length of time it had taken for them to be turned vertically and have new rock deposited on top. Hutton concluded a few thousand years was impossible. He was right. We now know the time gap is about 55 million years.

The signposted footpath to Siccar Point is just five years old, part of the overdue opening up of this part of the east coast to walkers. The route described here starts at Cove, just off the A1, but a shorter version can be had by starting further east at Pease Bay – 3.5 miles (5.5km).

Cove village marks the start and finish of the Southern Upland Way, which you follow south from the car park along the cliff tops above Cove Harbour. The rock here is red sandstone, the younger of the rocks seen at Siccar Point. Pease Bay is soon reached, the wildness of the landscape tamed somewhat by the holiday chalets. Follow the road down to a ford over the Pease Burn and a car park. The Southern Upland Way goes off south beside the burn, followed by a short uphill section of road to steps leading back to the cliff-top path.

The going is a little rough for a short distance, but the path improves and brings you round to a minor road leading to a vegetable processing factory at Old Cambus West Mains. Turn left and follow the minor road towards the factory to reach the Siccar Point path on the left after the road cutting. Follow the track and path past the ruins of St Helen's church and skirt the field edge to reach Siccar Point and interpretation boards. The rock formations are easily seen and appreciated from above, although a very steep and slippery path leads down beside the fence to the point.