Graham Lee – Archaeology Officer
Further to my last blog post, here are some more examples of enthralling LiDAR imagery from the North York Moors. As mentioned previously, the interpretation of features is not necessarily straight-forward since we are not seeing a photograph per se but a series of points joined together by a computer algorithm. A clear resemblance to ‘known’ features is a good start but often there is no substitute for checking the site on the ground where necessary, with the landowner’s permission.
Figure 1: Crag Cliff Wood near Grosmont
This image is from the 2016 This Exploited Land 25cm LiDAR (equating to c.16 data points per square metre). The This Exploited Land of Iron Landscape Parntership Scheme focuses on the 19th century ironstone industry in the North York Moors, one of the major sites for this was around Grosmont. This little four-fingered ‘hand’ near the centre of the image, just c.6.5m wide, is clearly a group of linear spoil tips leading out from a small excavation, perhaps a mining trial in the valley side? The linear runs of spoil, as tipped out of a barrow, are a very typical form associated with mining or quarrying sites. On steeper slopes, these are often tear-drop shaped.
Figures 2 and 2a: Rievaulx Village and the River Rye
This image from the Environment Agency 50cm LiDAR (equating to c.9 data points per square metre) shows the site of Rievaulx Abbey (Scheduled Monument) near the central bottom of the picture, with all the buildings stripped away to show the underlying and surrounding earthworks. There is a mass of detail to see here. To the north of the Abbey are the houses of the village with a whole series of platforms and enclosures visible on the valley side. Just below these is the line of the “Canal”, a watercourse dug by the monks to bring a supply of water from the River Rye into the Abbey complex. Surrounding the village are numerous hollow-ways (former routeways) and extensive remains of old quarries. The level earthwork platform, running North-South to the bottom right of the picture is the northern half of Rievaulx Terrace. The corresponding aerial photograph from July 2014, with the water courses and major earthworks (mapped by the Ordnance Survey) layers switched on, help to clarify the positions of some of these features, including the line of ponds leading down to what was the Medieval water-mill, now a private dwelling.
Figures 3 and 3a: Holmes Alum Quarry in Mulgrave Woods
This is a classic example of the value of LiDAR imagery. The aerial photograph from August 2015 shows trees blanketing virtually all archaeological detail but this is beautifully clear in the 10cm resolution LiDAR image from Spring 2017 (Durham University/North York Moors National Park Authority; equating to c.90 data points per square metre). You can see the three adjoining quarry scoops to the south of Sandsend Beck, with a mass of, presumably associated, earthworks just across the beck to the north-west. This is thought to represent the site of Holmes Alum Quarry which is recorded as operating from about 1680. Works here had ceased by the late 18th century / early 19th century when this area was landscaped as an arboretum for Mulgrave Castle. I am not aware that this site has ever been surveyed in detail on the ground – this imagery provides a very good starting point. Roasted shale is recorded as having been found in the area so the sites of roasting clamps and, possibly, even steeping pits should probably be there to be found. On the plateau to the south of the quarries is an area of Medieval and Post-Medieval Ridge and Furrow (ploughing) cultivation which is clearly visible.
For more information on LiDAR, have a look at “The Light Fantastic” produced by Historic England