Preston Bridge – the permissive footpath west of Preston Bridge on the north bank of Whiteadder Water leads the walker along the river past basalts, red sandstones and layers of volcanic ash (shown in the photo), all exposed on the river banks, until a low waterfall is reached after about a kilometre. A rocky exposure of volcanic breccia can be seen on the edge of the river and columnar dolerites are found on the hillside above. All these rocks are 360 million years old, close to the junction of the Devonian and Carboniferous periods.