3D Lidar landscape on Sketchfab: https://skfb.ly/pLzuM

This recent post on the LiDAR and Aerial Archaeology Group of Facebook sparked my interest.
https://www.facebook.com/groups/1508789132952429/?multi_permalinks=2398701490627851

The post describes an apparently circular enclosure revealed in the lidar dtm on the summit of the small wooded island in the centre of Grasmere lake. The author of the post suggested it might be prehistoric, and previously unrecorded.

Enhancing the lidar using a local relief model certainly shows a feature there which I was quick to confirm by that and other enhancements. The author suggested it shows a bank, a ditch, then another bank enclosing a sunken hollow at the top.

I still have doubts (and feel much less certain than 50:50) for reasons I will hopefully explain below. That said, the only way to be sure that this is something or nothing is a ground-truthing visit which perhaps the National Trust archaeologists will manage in the future. My reaction to these things is to explore the topography in as much detail as I can. Visitors to the island are not currently allowed so only remote methods are available. 

I can certainly confirm that there appears to be something shown on lidar images (here I call it a 'doughnut') on the south end of Grasmere Island. It appears to be approximately 50m in diameter, apparently enclosing the summit. 

The two images below are my favourite and most used methods of enhancing lidar images for archaeology use.

Feeling the need to explore the topography of the island (and this feature/anomaly) in more detail I had a look at the 3D visualisations which you can derive from the lidar data in several ways using QGIS. One of my favourite ways is using contours, here overlaid on a multi-directional hillshade.

From the level of the lake (about 61m above sea level), the south end of Grasmere Island rises to a peak (75m ASL) which occupies a broad ridge running NE-SW from a slightly lower second summit on the N part of the island. With a contour interval of 0.5m, the 14m between the water level of the lake and the summit are modelled by 28 contour lines which closely define the shape and altitude of the island and show us where the slopes are steepest.

A second ridge runs steeply down from the main summit SE towards the lake where a building is indicated on the map (locally described as a barn). It is the site of William Wordsworth's poem: Inscription for the House (an Out-house) on the Island at Grasmere.

The question I pose is: does the lidar show ditches and banks encircling a summit (perhaps a small fortified enclosure) or something more natural?

Below using the elevation profile tool showing a section across the southern summit. This suggests a series of steps, about 2m high to the NW of the summit and they certainly don't model a doughnut ring or hollow centre. There are hints of small valley features running along the hillside just below the lower step on the W and NW sides, but these don't continue round the contours on the steep E side.

You can clearly see the two upper steps or ledges in the elevation profile shown below.

Using a contour interval of 0.1m (perhaps pushing the resolution a little too far) I believe we can duplicate all the elements of the island doughnut, apart perhaps for the ditch (if that is what there is) which lies just below the second steep slope NW of the summit ridge. The contours confirm what we see using a slope analysis from lidar. In this representation, the steepest slopes are rendered as black, and flatter areas as white and lighter shades of grey.

The same of course can be demonstrated in a 3D model but is best when you can look yourself rather than on a screen capture from a single angle screenshot as shown below. The interactive model from which this screenshot was taken is freely available on Sketchfab and doesn't need to be downloaded.

Does any of this prove that the features are natural rather than man-made? Maybe not, but they give me huge doubts that only a ground observation can confirm.

If the feature is of natural origin then how might it be explained?

The contour model suggests to me something called trap topography - a step-like landscape formed by layered volcanic rocks. It occurs when alternating layers of hard, erosion-resistant lava and softer, crumbly volcanic ash weather away at different speeds. The hard lava forms steep cliffs (scarps), while the soft layers form flat shelves (benches), creating a natural staircase. There are certainly hints of this in the neighbouring hills and it is well known in the volcanic hills of the Lakes. I think similar features are visible, for example, in the area around Hardknott Roman Fort.

There is much geological data about this area of the Lake District here:
https://webapps.bgs.ac.uk/memoirs/docs/B01517.html
I can find little information about the topography and geomorphology of Grasmere Island itself, although a volcanic origin does appear likely.

Is what we are seeing in the lidar here a small scale version of trap topography along with some natural drainage? Now I wonder: what are those three small mounds at the N end of the island, NW of the southern summit?

My thanks to Adam Ibbotson for spotting this feature and for an interesting and stimulating post. They happen very rarely on Facebook. The analysis and interpretation here are of course my own.

The three images below show contours at interval of 0.5m created in QGIS from dsm lidar.

To enable further exploration of the Lowther Castle Estate I created a 3D Lidar landscape model on Sketchfab.

Today I am looking at the extensive parkland around the ruined mansion of Lowther Castle.

Wikipedia: Lowther Castle

Historic England Grade II Listed: 1000668

At the southern end of the estate, enhanced DTM lidar highlights two mounds (in white) surrounded by ditches (in black) located in grassland, just S of a large (perhaps recent) pond. The mounds are about 15m in diameter and about 0..5m high. They look very like Bronze Age burial mounds (tumuli or barrows). But are they a bit too neat to be prehistoric? The Historic Environment Record describes them as: "Possible ring ditches (circular or near circular ditches which may be the remains of ploughed out round barrows, round houses, or of modern features such as searchlight emplacements) of unknown date that appear as crop marks."

It also provides an alternative explanation for the features as old circular coppices, apparently "shown on a map of probably 18th century date kept in the Lowther Estate Office that when Lowther Castle was rebuilt in 1809 the Landscape Architect would have been of the opinion that the older circular coppices detracted from the newly-planted avenue as it appears from the Castle window".
Lake District National Park HER: 5375

There are several such circular ditched features in the northern part of the estate but they are nearly all of larger diameter and without raised central mounds. They look much more like tree planting rings than these do.

The two features shown near the pond are some 2.5km SW of the ruined mansion, nowhere near planted avenues, and blocked from line of sight by much higher land. If they really appear on the 18th century map as tree rings there would be no doubt. There is no hint of rings on the 1st edition OS map (c.1860) although that map suggests the pond may have been created on a site of clay extraction used by a nearby tile works. Evidence suggests that the features have been there for some time. Perhaps, rather than for tree planting, they are just fake archaeology created as special features within the parkland. They would certainly have been visible approaching the castle on Emperor's Drive from the former lodge on the A6.

On the prehistoric side of the argument, an archaeology report of part of Lowther Park by Oxford Archaeology North published in January 2005 states that "... the earliest identified activity within the vicinity of the park is from the Bronze Age: there are a pair of round cairns just south of the park Round Hill (NY 541 219)".
Gajos, Hannah (2005) Lowther Deer Park, Cumbria. Archaeological Survey and Evaluation.

Below lidar image (using DTM to remove trees) to compare the two mounds with several probable ditched tree-ring plantation features in the area of Lowther medieval village and the Castle Stead (Castlesteads) possible ring-work situated just north of the ruined mansion of Lowther Castle.

Includes St Michael's Church, Castle Stead (a possible Norman ring-work castle) and the deserted medieval village of Lowther, all situated north of Lowther Castle (the name of the ruined mansion house) above a steep bank above the River Lowther. Note that the several perfect circular ditched enclosures are likely former tree ring plantations often overlying earlier features.

The earthwork called Castle Stead is a rectangular ramparted enclosure 30m by 25m with very substantial ramparts 4-5m thick standing to 3m in height. The rampart is much thicker in the SE corner, possibly being the location of a tower. There are two possible entrances, one in the south and the other in the east. The predominantly earthwork form of the structure, the paucity of collapsed masonry and the possible twelfth century date would suggest that this was not a peel towe and is too small to have been a motte and bailey, but could have been a timber ringwork castle.
"The ancient village of Lowther was heretofor considerable, consisting of the hall, the church, the parsonage house, and seventeen tenements, messuages, and cottages, all of which were purchased by Sir John Lowther, in the year 1682, and pulled down to enlarge his demesne and open the prospect of his house, for they stood just in front of it’.

Wikipedia:Castle Stead

Gatehouse - Castle Stead, Lowther

Lancaster University: Lowther Medieval Castle and Village

Castle Studies Trust - Geophysical survey and excavation (2023)


3D Lidar landscape on Sketchfab:
  DTM: https://skfb.ly/pK9Ls
  DSM: https://skfb.ly/pK9KR

Cerne Abbas, Dorset.

Location: ST 6667 0168

Scheduled Monument: Hill figure called The Giant

Scheduled Monument: Earthworks on Giant Hill

National Trust Archaeology Record: MNA138903

Hill figures are unique to England and are found on the chalk scarp slopes across southern Enland with a few outlying examples in Yorkshire. Most of the figures are horses or military badges but there are two human figures, the Long Man of Wilmington (E Sussex) and the Cerne Abbas Giant.

The Giant is a 55m high chalk-cut figure, picked out in regularly replaced chalk, standing on the SW steep slope pf Giant Hill (Trendle Hill) above the viallage of Cerne Abbas and its abbey. The Giant carries a club in his right hand and has been called "Britain's most famous phallus" although some evidence suggests he wasn't always depicted without clothes.

There has been much speculation among antiquaries and archaeologists regarding his age, identity and meaning. The first known historical refernce is to a repair of the Giant in 1694. There is no mention of the figure in earlier records, notably a 1617 survey of the area by John Norden, who was famously thorough. There have been speculation that the Giant may have been constructed as far back as the prehistoric, with other theories suggesting Roman, early or late medieval periods.

Since 1920 the Giant has been in the care of the National Trust. The small excavations undertaken in 2020 were designed to collect samples of snail shells and soil at various layers of his construction which could provide accurate dating evidence. Quartz grains retrieved and kept in the dark can be dated using OSL (optically stimulated luminescence).

Examination of snail shells suggested the hill figure is "medieval or later". Snails dating only from the Roman period (brought from France as food) were not found at the site, while species first found in England from the 13th and 14th centuries were found. The OSL study yielded a date range for construction of 700–1100 CE in the early medieval to late Anglo-Saxon period.The discovery  was featured in Series 9, Episode 5of the BBC series Digging for Britain.

National Trust SW Archaeology blog:

   Dating the Cerne Giant Results!
   
   Cerne Giant the OSL dates

Below the specially flown drone over the Giant and adjacent area to get a good LiDAR survey of his earthworks (Downland Partnership).

3D lidar landscape on Sketchfab: https://skfb.ly/pHFJL

Wikipedia: Cerne Abbas Giant

https://historicengland.org.uk/research/results/aerial-archaeology-mapping-explorer/

Find area of interest using ST666016 in a grid reference search.

Styford (Bywell) [NZ 01556249] Mound. (1)

A large, artificial conical-shaped mound with a strong ditch surrounding on three sides. On the south there is a steep, natural slope to the river valley below. The mound is 5m high on the east, and the summit slopes slightly upwards to be 6.6m high on the west. The ditch is deepest and widest on the north where the approach is from higher ground. The whole earthwork has been mutilated by much quarrying. Rig and furrow ploughing runs up to the perimeter of the ditch. There is no apparent outer bank. Situated with a commanding view to east, south and west, the earthwork is defensive, and is quite characteristic of a motte. (2)

Description and published survey (25 inch) correct. (3)

Styford motte was built in the 12th century, and was the caput of the Bolbec family. (4)

Reference number: N10057

Henry I granted the lands here to Walter de Bolbec (d c.1133), which remained with his descendants until 1262. He may have founded the castle. This is one of the suggested sites of the castle of Tiefort, which was mentioned in 1216.

Gatehouse Gazeteer: 2445

Is there a faint outline of something in the flat field just N of the Styford Motte (NZ 0166 6273)? Very difficult to make this into anythying other than perhaps a possible plough-levelled enclosure, or lumpy, disturbed ground. It is visible on both dsm and dtm lidar. However, I have been unable to find any further evidence to support the observation such as crop-marks on available aerial photos or historic satellite imagery. The Historic England aerial mapping explorer is still blank in this area.

The trouble with this theory is the presence of even fainter and similar marks in the surrounding fields and nothing particularly representative of a deserted medieval village that we see elsewhere in Northumberland.

See K2P: N10068 

Wrathmell, S, 1975 is given as reference 6 and is quoted in the HER record as follows:

There is a similar 'disturbed' area visible on lidar between Styford Hall (built c.1800) and the old ford across the River Tyne within the emparked area (NZ 0200 6199). This could be the location of the buildings referred to on the 1708 and 1749 plans. Being close to the river, it would certainly have sufferered in the Great Flood of 1771.

Wrathmell could have been correct though in assuming that the early medieval deserted village was much higher above the river haughs, somewhere up near the motte.

There is little remaining medieval rig and furrow in either of the two locations although a small area can be seen on lidar running up to the NE edge of the ditch surrounding the motte.

Warden Castle ('Motte')

Location: NY 9119 6652

Should this be better described as a ringwork rather than a motte?

Elevation profiles from lidar (dtm, 1m) and 1m contours shows that the castle mound is raised by at most 2m.above the level of the hillside from which it has been separated by a cut ditch.

Description

The motte castle at Warden is a well preserved example of a monument type which is rare in Northumberland. Evidence relating to the nature and duration of its use will be preserved and hence the site will contribute to the study of the Norman Conquest of northern Britain.

The monument includes a Norman motte situated on the top of a natural hill commanding a prominent position above the confluence of the rivers North and South Tyne. The conical motte, which stands at a height of at least 3m, has been constructed upon a high promontory in order to utilize the steep natural defence on the north, east and south sides and it is only on the west side that artificial defences have been dug. These consist of a ditch, which isolates the motte from the rest of the promontory, varying in width from 2.5m to a maximum of 5m. The motte is flat-topped and oval in plan measuring 35m by 19m. A bank has been constructed along its western edge which now stands at a height of 0.5m. There is a causeway across the ditch in the south-western corner of the monument, the presumed site of an original entrance. The motte was constructed in this strategic position in order to dominate the passage of traffic across the rivers. (Scheduling Report)

"Measures 35 paces x 25 paces, cut off by a ditch from a sort of promontory, by the side of a deep fissure in the declivity." An oval Camp, immediately north of the Vicarage, at outpost from Warden Hill (NY 96 NW 17) to watch the fords of the river (MacLauchlan 1858).

"A track comes up from the road and passes the Camp as a hollow-way on the south, and there is also an entrance with a ramp up to it on the north side, but whether this last is modern or original cannot be said. On the west there is a ditch; on the east there is a very steep slope down to the level of the road." (Hedley 1923-4).

An earthwork situated in an excellent commanding position on a promontory, overlooking the confluence of two major rivers (North Tyne & South Tyne). The promontory has been isolated by the construction of a strong ditch across the neck, and heightened so that the level top now stands 2.0 m., above the level of the ground to the NW. A defensive bank has been erected south-east of the ditch, elsewhere defences are natural and precipitous. A probable original entrance is visible in the west face of the work, a causewayed entrance to the north is sharply cut and possibly later, there are no signs of internal occupation, the present nearest water supply is a well 70.0 m. to the NE., perambulation revealed no traces of out-works. The hollow-way, refd. to by Hedley, is a natural steep sided ravine.
From the construction and topographical situation the earthwork is adjudged to be a Motte.

Warden Church (150.0 m. to the S.E.) is indicative of Saxon & Norman occupation in this area. (See NY 96 NW 13 & 40) Similar earthworks of this nature have been encountered in this county at Wooler (NT 92 NE 59) and Lowick Low Stead (NU 03 NW 4) (F1 FDC 3.5.56). (PastScape)

Comments

Sometimes described as partial ringwork. The strategic position, overlooking fords should be noted but it dhould also be noted the parish church is of Saxon origin and, therefore, it is likely the Norman castle is sited on the site of a Saxon manorial site.

Gatehouse Gazeteer: 2866

Keys to the Past: N8559

Scheduled Monument: 1011417

"English historian, Davison, theorized in 1967 that ringwork castles, rather than mottes, were the key castles used by the Normans in the conquest of England, and Arbuthnot states that this theory has been confirmed by archaeological and historical evidence and is now widely accepted (Arbuthnot 2010:35; Davison 1969;19-24)."

When is a ringwork a ringwork? Identifying the ringwork castles of County Wexford with a view to reconsidering Irish ringwork classification. Grace Dennis-Toone (2019). Thesis.

Historic England (2018). Earthwork and Timber Castles: Introductions to Heritage Assets. Swindon. Historic England.

Location: NY 8611 7678 

Wark-on-Tyne. Northumberland Extensive Urban Survey. Northumberland County Council and English Heritage (2009).

Mote Hill or Wark Castle.

The settlement [of Wark] lies around a ‘T’ junction formed by the B6320 - which runs along the west bank of the river between Chollerford, four miles to the south and Bellingham five miles to the north - and a minor road which runs up the east side of the river before crossing at Wark. The presence of this crossing, initially a ford, must have been a major influence on the site of any settlement, as would have been a prominent plateau, Mote Hill, just to the south of the crossing, a naturally defensible position and one which seems to have been enhanced during the 12th century as an earthwork castle.

Mote Hill was formed at this period [recession of last Ice Age] as a drumlin and is made up of contorted bands of gravels and sands. Terraces have been formed along the valley above flat haughlands.

A notable omission amongst any records is specific reference to a castle on Mote Hill.

Mote Hill, a relatively flat-topped plateau with steep edges to all sides, lies immediately to the south of the village of Wark and the bridging point of the river. The Warks Burn runs into the North Tyne a little to the south of the hill, a confluence which may have provided the name of the feature ‘mote’ is Anglo Saxon for a meeting place, possibly of the waters.

Mote Hill Farm, mostly of 18th and 19th century date but with one building in its ranges dating to the 17th century (see Appendix 3 for Event no 320) covers the north-west quarter of the plateau and succeeds a post-medieval manor house constructed by Francis Radcliffe in the 1660s and 1670s.

The hill, and specifically the area around the farm, is thought to be the location of a motte and bailey castle, or at least a motte, possibly constructed as the seat of Prince Henry of Scotland who was created Earl of Northumberland in 1139 and presumably utilised as a defensive work during the time Wark was within the Liberty of Tynedale after 1157, although of the medieval references to defensive works at Wark, none specifically mention Mote Hill. Two modern published accounts describe earthworks on Motte Hill surviving around the mid-20th century; Dodds mentions ‘parts of an outer rampart still to be traced in short sections on the north and south’ (Dodds 1940, 37) amplified by Hunter-Blair who ...two fragments of banks are still visible, one on the north side against the wall surrounding the stockyard, and the other at the south-east corner of the hill-top and also mentioned that ‘the ditch between motte and bailey can...be traced as a shallow depression crossing the farmyard’ (Hunter Blair 1944, 141-2). None of the earthworks or depressions described is necessarily associated with a motte or a motte and bailey. The elusive nature of the earthworks is reinforced by the absence of any rendition of them on the series of 25” to One Mile Ordnance Survey maps, the surveyors for which were normally so assiduous inrecording earthworks.

A general assessment of the site by Ryder in 2002 concluded that the evidence for the castle was not certain (event No ???). Archaeological evaluation prior to conversion of the farm ranges on the hill to residential use (Event No 13254), and an archaeological watching brief (Event No 13612) during these redevelopments between 2003-2005 also failed to locate any earthwork build up or artefactual evidence to confirm the interpretation of the site. It is possible that the motte has now been completely levelled, or that it lies elsewhere on the plateau. Terraces on the south slope of the hill could possibly be of some age.

Speculation that Mote Hill may have been a focus for a prehistoric settlement is as yet unproven.

Keys to the Past: N7746

Gatehouse Gazeteer: 2875