Climate change, increasingly industrialised agriculture and changes in the crops being grown are influencing our knowledge of the past. The relatively extreme weather patterns that we are experiencing in Britain influence the way that arable crops grow revealing archaeological features buried and forgotten often for thousands of years. These crop marks, a function of contrasts between the undisturbed subsoil and cut features such as ditches and pits or structural foundations result from differential growth patterns which have influenced the development of the root system and thus the speed at which crops ripen or suffer from stress in dry spells like we are having at present.
Air photography over the last century has been the biggest single contributor to our knowledge of the scale of past settlement in Britain. It has become blatantly obvious during the last twenty years that new and previously unknown features have been appearing even in very extensively studied landscapes and that their appearance owes much to the increase depth of ploughing that has accompanied the introduction of ever bigger farm machinery. Deeper ploughing cuts away and disturbs buried archaeological deposits such as the floor layers of prehistoric houses, mixing the material in the plough soil and leaving only truncated features beneath. Pits, ditches, wall footings or post-holes that cut deeper than the depth of the plough will ultimately be all that survives this modern hyper mechanised agricultural revolution and will, if we are not careful, be all that is left to help us understand human interaction with the British landscape over the last 12,000 years. A casual look at the Yorkshire Wolds in winter, when large areas of ploughed fields can be seen, indicates the levels of plough damage that have changed the thin plough-soil to a material mostly made of rock. The Wolds are becoming whiter every year as more chalk is broken up and added to the plough-soil, the chalk of the Wolds has not been so exposed since the last glaciers receeded.
The crops are late and the weeds confused but as the weather has settled down, leaving many in a state of disbelief, the crops have started to turn, producing crop marks that were last seen emerging at the beginning of May last year, before the deluge began. Field archaeologists are as tied to the weather as farmers, even more so if they are also engaged in aerial archaeology, if this present dry hot spell continues we would expect to see crop marks all over Britain and new discoveries made every flight; filling in gaps in the human landscape that could only be otherwise approached with a vast investment in ground based geophysical surveys and on the ground investigation. The combination of factors of climate, crop, soils, local and short term weather creates conditions that are effectively unique every day, conditions that may expose vast areas of hidden archaeology even if most often we are unable to securely date and precisely interpret what we see.
Seen from the air the landscape wears the effects of human intervention:
The pattern derived from the resurgence in the use of garden allotments
Enclosures and track-ways from a probable Iron Age or Roman settlement cut through by a now abandoned railway line and trapped between a modern housing estate and a golf course.
What appears to be an Iron Age farmstead with a single roundhouse in a rectangular enclosure in an environment with poor drainage as demonstrated by the network of field-drains which cut through both the enclosure and what appears to be a track-way and other less clear features in the left hand part of the frame.
Some people, I understand, believe that crop circles are the product of Aliens, if this is the case one wonders what sort of ambitions this particular crew had when they created these marks in a field near Poppleton just outside York. I suppose this provides some context for my four year old who refers to Crop-marks as Crock Marks..or maybe he is saying something else.