The recent record-breaking heatwave and drought across the British Isles has led to the discovery of a number of previously unknown sites due to cropmarks that have become evident. Cropmarks are visible differences on the surface of the ground which occur as a result of differential growth caused by archaeological remains under the ground.
How do cropmarks occur?
If there was a historical excavation at a site that has since been filled in (such as a moat or a ditch) the topsoil is deeper and provides the plants more nutrients and water, allowing the plants above to grow more vigorously than elsewhere. Conversely in areas where there has been building work like the walls of a villa or fortification the topsoil is shallower and hence provides less nutrients and water for the plants above stunting their growth.
This differential growth becomes a lot more obvious in extreme weather conditions like those currently being experienced across the British Isles. Dozens of previously unknown archaeological sites have shown up in recent aerial photographs. In Scotland discoveries include Iron Age structures and a temporary Roman camp. In Wales evidence of a previously unknown Roman villa built on the same land as a known prehistoric settlement has been discovered and in Ireland what is being labelled as a new Stonehenge has been discovered.
Hopefully in time details of all these finds will begin to surface and we will revisit them in depth.