Swaledale is the product of millions of years of Earth processes and a few thousand years of human activity. Natural processes, geological and geomorphological, still continue to shape the landscape. Sinkholes and karst-weathering continue to form as the limestones gradually dissolve away. The River Swale and associated becks are continuously eroding, transporting and depositing material as gravel bars and forming terraces. The gravel carried by the rivers and streams in Swaledale does not only represent the underlying Carboniferous bedrock but is frequently enhanced by lead mining waste in many areas.
A lynchet is an earth terrace found on the side of a hill (often south-facing). Lynchets are a feature of ancient field systems during the medieval era and examples can be found all over the Yorkshire Dales. The size, location, spacing and number of rows of many strip lynchets indicates that most were created by farmers to maximise the use of land for agriculture. In Swaledale, strip lynchets can be found on the banks of the River Swale near to Reeth. Some of the lower terraces may be former river terraces made by the River Swale.
Wandering through Swaledale, it’s hard to imagine that the area was once a much more industrial landscape. Cast blocks of lead, or ‘pigs’ have been found in the Yorkshire Dales dating back as far as Roman times, when British lead was exported around the Roman Empire for use on roofs and to make water pipes. The scars of lead mining are left in the landscape today not only the ruined buildings, mines and mine waste but also the hushings that cut down hillsides, such as Gunnerside Gill. A hush is where a dam was built at the top of the mining area, collecting water until the dam was broken and water scoured the topsoil below, taking with it loose stones and exposing the mineral veins of lead (galena) and zinc (sphalerite). Levels were then dug into the hillsides to extract the minerals through caves such as Devils Hole near Grinton smelt mill. Bunton Hush at Gunnerside Gill extends up the steep fellside to the moor top. Galena extracted here was returned back through the levels to emerge at Old Gang smelt mill some 2.5 miles away. This hushing exposes several limestone beds and can enhance localised erosion and introduce instability into the hillside with scree slopes of loose limestone blocks and small landslips. The occurrence of mine dumps and mine tailings are frequently unstable and regularly contribute limestone blocks, gravel, sand and mud to the becks and rivers.
North Hush, which runs steeply down the western flank of Gunnerside Gill, might well be mistaken for a natural ravine, but it is actually industrial. A productive vein of galena was discovered here running roughly west to east, and the hush was developed along it by digging with pick and shovel, along with repeated flooding from dams constructed near the moor top.
The activities of people living in Swaledale and working here for millennia have had a profound influence on the landscape. Lead mining has played a major role in influencing the landscape, but equally agriculture has impacted through woodland clearance, building dry stone walls, liming of fields, and the development of farming settlements.