Thursday, 31 August 2017

Missing Lincs? Some lost islands along the Lincolnshire coast

The following post offers a quick survey of some of the lost islands off the medieval and earlier Lincolnshire coast. As has been discussed in a number of previous posts, the coastline of Lincolnshire has changed considerably in both the historic and prehistoric eras, and part of this change has involved the creation and subsequent loss of a number of coastal islands to both the sea and the land.

The coastline of Lincolnshire in the thirteenth century, drawn by C. R. Green after S. Pawley, Lincolnshire Coastal Villages and the Sea c. 1300–1600: Economy and Society (University of Leicester PhD thesis, 1984), with slight modifications. This map includes one depiction of the possible number and extent of both the offshore barrier islands that are often thought to have protected the coast of Lincolnshire through until the thirteenth century and the calmer, lagoonal conditions that they are suggested to have created to their west, protecting the Lincolnshire coast from the full erosive force of the North Sea.

The offshore barrier islands

The melting of the ice-sheets after the last glaciation saw the North Sea basin—a landscape now usually termed Doggerlandgradually, and occasionally not-so-gradually, inundated by the rising tide. Over the course of several thousand years, the steadily advancing coastline moved towards that of modern-day Lincolnshire until it reached something close to it in around 6000 BC (approximately the same time that the glacial-era land-bridge between Britain and the Continent was finally severed). For the Lincolnshire coast, one major effect of this was the drowning of the Mesolithic forests that once covered the region—the remains of the submerged forest are still visible along the coast at very low tides and its inundation has been dated to 6174–5961 cal BC at Theddlethorpe, for example. Even more significantly from the present perspective, the marine flooding also created offshore islands from the slightly higher ground that once lay to the east and north of the modern Lincolnshire and Norfolk coastlines (probably originally part of a glacial moraine left by the retreating ice-sheets on what was then the land surface). These islands extended south-eastwards from Spurn Point and are believed to have shielded the Lincolnshire seaboard from the full ferocity of the storms and tides of the North Sea, creating a sheltered tidal lagoon between themselves and the main coastline that was characterised in part by saltmarsh, wide sand and mud flats, and tidal creeks and estuaries.(1) As was discussed in a previous post, this protection appears to have finally failed during the 1200s when the offshore islands were finally destroyed by an unprecedented series of storms and floods in that century. The debris that resulted from their destruction is usually thought to have been cast up along the foreshore of the Lincolnshire Outmarsh as broad 'storm beaches' and sand dunes, as at North Somercotes.

The Lincolnshire Marshes in the pre-Viking period (drawn by C. R. Green, contains British Geological Survey materials © NERC 2014). Louth is marked on the map to aid with location. Light blue represents freshwater wetlands and saltmarsh, whilst dark blue is used for the sea and main creeks/rivers in this region; note, the extensive areas of sand, silts and channels shown on the previous map are not depicted here but would have been present. Key sources of information used in its creation include the British Geological Survey's maps of this region; D. N. Robinson's map of Lincolnshire's 'Saxon Shoreline' from The Book of the Lincolnshire Seaside (Buckingham, 1981); H. Fenwick, The Lincolnshire Marsh: Landscape Evolution, Settlement Development and the Salt Industry (PhD Thesis, University of Hull, 2007); N. G. Berridge and J. Pattison, Geology of the Country Around Grimsby and Patrington (London, 1994); and the 1628 (Mercator) and 1645 (Blaeu) maps of Lincolnshire.

The geology of Stain Hill and the surrounding area, set against a present-day streetmap, showing the island of Stain Hill surrounded by marine alluvium; click image to view a larger version. Yellow represents marine alluvium; green Devensian glacial till, and purple Devensian glaciofluvial deposits. Image taken from the BGS Geology of Britain Viewer, licensed under an Open Government Licence 2.0: contains British Geological Survey materials © NERC 2014.

Stain Hill and other 'islands' in the pre-Viking coastal zone

The post-glacial marine inundation did not simply cease when it reached the area of the modern coastline of eastern Lincolnshire in around 6000 BC, but rather continued to press inland for millennia to come. The Mesolithic land surface that it encountered was comprised of a thick undulating layer of glacial till that had been deposited as the ice sheets retreated northwards at the end of the last 'Ice Age', around 15,000 years ago. This glacial till still forms the surface of the Middle Marsh of Lincolnshire, between the Wolds and the present-day flat coastal plain, but it is buried by marine deposits up to 17 metres or so thick on the coastal Outmarsh. As this undulating landscape underneath the present-day flat Outmarsh was gradually flooded by the sea, some former high points and minor hills were eventually surrounded and became 'islands' and peninsulas of dry land in this new coastal zone. Many of these were subsequently drowned in turn by the rising tide, but some were sufficiently elevated to have remained dry right through until the maximum extent of the inland penetration of the sea was reached in around the fourth- to sixth-centuries AD, when land up to 4.22 to 4.52m above present-day sea-level was flooded in southern Lincolnshire and Romano-British sites on the coastal marshes of the eastern Lincolnshire were buried under two to three metres of marine silt.

One of these coastal zone 'islands' surrounded by the upper levels of the marine silts was Stain Hill near Mablethorpe (depicted on the British Geological Society map included above). This small island of glacial till and gravel rises from the surrounding marine alluvium to reach a maximum height of 9m above sea-level and has been the site of a number of interesting finds, not least a large group of Late Roman coins and a locally notable grouping of Anglo-Saxon material that is perhaps indicative of the presence of some sort of significant settlement or estate centre located on this elevated point in the coastal marshes. Further south are found other small islands of higher glacial till standing above the marine alluvium of the flat Outmarsh, which can probably be identified as the original locations for Sutton-in-the-Marsh/Sutton-on-Sea (given that this is an Anglo-Saxon name meaning the 'southern farm' or similar, perhaps named in relation to the possible central place at Stain Hill and part of its estate?) and Hannah (another Anglo-Saxon name which involves Old English ēg, 'island', plus hana, here either 'a cock, rooster' or a related personal name).

To the east of Alford there is another, much larger island of glacial till surrounded by the marine deposits of the Outmarsh according to the British Geological Survey, now occupied by the villages of Thurlby, Mumby, Anderby, Huttoft and Cumberworth. Once again there is evidence for Romano-British and Anglo-Saxon-era activity here, not only from the names Huttoft and Cumberworth (which are Old English in origin, with the first element of the latter being potentially OE Cumbre, 'the Britons, Welsh'), but also from metal-detected finds and archaeological excavations too. Thus chance finds from Cumberworth parish include part of a Late Roman crossbow brooch, indicative of the presence of the Late Roman military in the very late fourth or early fifth centuries; a Late Roman clipped silver siliqua of Arcadius, struck at Milan in c. 395–402; and an Anglo-Saxon silver coin of c. 680–710. At the same time, excavations at St Helen's Church in the village of Cumberworth itself have seen the recovery of 26 burials from a mid- to late Anglo-Saxon cemetery that was in turn overlain by a timber church that was probably demolished by the end of the tenth century. Finally, to the south-east of this large island were a scattering of smaller dry glacial till islands in the coastal marshes heading out towards the open sea, including one now occupied by the village of Hogsthorpe. Again, these seem to have seen activity in the Anglo-Saxon period, with finds of metalwork and even high-status gold pieces.

The former islands east of Alford; click here for a larger version of this image. The green and purple colours represent glacial deposits standing above the surrounding marine alluvium, coloured yellow. The main former island is presently home to the villages of Thurlby, Mumby, Anderby, Huttoft and Cumberworth, with a scatter of lesser islands in the old coastal marshes (that is, former high points in the underlying post-glacial landscape that were never inundated by the sea) then strung out eastwards towards the open sea. Image taken from the BGS Geology of Britain Viewer, licensed under an Open Government Licence 2.0: contains British Geological Survey materials © NERC 2017.

An Early Anglo-Saxon gold disc pendant of the  seventh-century, decorated with applied filigree beading. Found on an island in the coastal marsh in the 'Skegness area' of Lincolnshire (image: PAS).

A 1541 map of the Humber estuary, which seems to show dry islands around Spurn Head and in the middle of the Humber; click here for a larger, zoomable version of this map (image: British Library). It seems that the islands depicted are intended to be read as dry islands, rather than low-water sand banks and other features; certainly, this is the impression that their colouration gives, which is that of the land rather than the sand (a large area of sand is shown and labelled on the southern bank of the Humber, opposite Spurn Head). Moreover, if this map were a purely low water map showing sand banks and the like, then we would expect it to show considerably more features in the Humber estuary than it does—a comparison of this map with the only slightly later 1595 Cecil map supports this contention, as this is a low water map and shows the Humber estuary full of such features. 

Ravenserodd, Burcom, the Bull, and Sunk Island: former islands at the mouth of the Humber

Looking northwards to the mouth of the Humber, a number of islands are recorded, some more ephemeral than the others. Perhaps the most famous, or infamous, of these is the medieval pirate island of Ravenserodd, which thirteenth-century witnesses describe being thrown up by the waves in the mid-thirteenth century somewhere in the vicinity of Spurn Point:
By the casting up of the sea, a certain small island was born, which is called Ravenserodd, which is distant from the town of Grimsby by the space of one tide. And afterwards fishers dried their nets there, and men little by little first began to dwell and stay there, and afterwards ships laden with divers kinds of merchandise began to unload and sell there...
By 1251, a charter for a market and a fair at Ravenserodd had been obtained, and by 1290 the town and port of Ravenserodd had begun to seriously threaten the trade of nearby Grimsby, with contemporary Grimsby folk declaring it a pirate island at the mouth of Humber, preying on passing shipping. Indeed, the demise of this town (which received its borough charter in 1299) during the following century was widely attributed to its evil character—as one fourteenth-century chronicler put it, 'by its wicked works and piracies, it provoked the wrath of God against its self beyond measure' and was consequently swallowed by the sea. This reclamation of the island and town of Ravenserodd by the waves seems to have begun in the 1330s, with over 200 buildings and properties lost by the mid-1340s, and by 1362 the once-prosperous town was 'destroyed to its foundations' and lay derelict, with its exact former location nowadays being uncertain.

The 1595 Cecil map of the Humber and the east coast of Yorkshire, showing all the sand banks and 'dry sands' then within the estuary; 'The Bull' is described as a 'dry sand' on this map and Burcom appears simply as a sand bank. Click here for a larger version of this section of the image or here for a zoomable version of the entire map (image: British Library).

Another, less dramatic case is that of Burcom, which now exists as a sand bank close to the south shore of the Humber near Grimsby. The name itself may be old and has been thought likely to reflect OE *burg-cyme or *burg-cuma, meaning either 'arrival at the town' or 'arriver at the town''—the latter involving the personification of the sand or island—in reference to its close proximity to the medieval borough (burgh) of Grimsby. Its exact status is open to some question, as whilst it is presently a sand bank and is described as such on the 1595 Cecil map of the Humber, on some nineteenth- and early twentieth-century maps and charts it seems to be shown as a dry sand or even an island, suggesting that its character may well have fluctuated over the centuries.

Similarly worthy of note is 'The Bull' or Bull Sand, a sand bank in the middle of the Humber mouth. This is shown as an island and labelled on the 1541 map of the Humber included above and is described as a 'dry sand' on the 1595 map, but it conversely isn't plotted on those nineteenth-century maps that show Burcom as an island or dry sand and the Bull isn't shown as a dry sand in 1707 either; it is currently the site of Bull Sand Fort, a four storey steel and concrete fortification originally armed with four 6-inch guns and built 1915–1919. Finally, mention ought to be made of Sunk Island, a parish on the north bank of the Humber. This initially developed as another dry sandbank in the middle of the estuary before it was embanked and reclaimed from the mid-seventeenth century onwards, becoming first an island before the channel between it and the mainland silted up in the eighteenth century and was also subsequently reclaimed. Sunk Island became a parish in 1831 and further reclamations extended the land here through until 1970.

Samuel Thornton's 1702-1707 chart of the Humber, showing Sunk Island when it was still an island and Burcom as what appears to be a partially dry sand, or nearly so; conversely, Bull Sand appears to have ceased to be a dry sand by this point. Click here for a larger version of this chart (image: New York Public Library).

An Ottoman Turkish map of the Humber, dated 1803/04, showing Sunk Island joined to the north bank and what seems to be Burcom shown as a semi-island. Click here for a larger version of this map (image: Library of Congress).

Map of the Humber in Élisée Reclus's Universal Geography IV: The British Isles (London, 1876), p. 235. This shows Burcom as an island in the Humber to the north of Grimsby and Sunk Island attached to the north bank.  Click here for a larger version of this map (image: Internet Archive).

Marshchapel, Conisholme and Somercotes: salt making and sand islands on the north-eastern Lincolnshire coast

The final set of lost islands are located in north-eastern Lincolnshire, in the Outmarsh around Marshchapel and Somercotes, and perhaps the most recent and interesting of these are the saltern mounds of this area. By the tenth century AD, the edge of the coastal zone had clearly moved eastwards from its earlier inland maximum to somewhere in the vicinity of Marshchapel, given that a Late Saxon saltern has been excavated a little to the south-west of the church that was processing sea-water brought to the site by an artificial channel. Over the medieval period, salt making continued in this area and gradually moved eastwards, as saltern mounds were created from the waste products of the process and the land in between them was reclaimed, pushing the coastline and its salt-making industry eastwards. These saltern mounds, some 6m high and 20m across, initially acted as dry islands in the coastal marshes, and as each generation of mounds were reclaimed they became part of an odd, hilly landscape on the landward edge of the coastal zone, although over time the majority have been reduced by ploughing and remain visible only from the air. The industry here was still in operation in 1595, when William Haiwarde's drew a detailed map of Fulstow and Marshchapel, reproduced below, and described the eastwards movement of the mounds as follows:
The round groundes at the Easte end of Marshchappell are called mavres and are firste framed by layinge together of great quantities of moulde for the making of Salte. When the mavres grow greate the Salt makers remove more easte and come nearer to the Sea and then the former mavres become in some fewe years good pasture groundes. Those that have the Cottages nowe upon them are at the presente in use for salt.
Extract from  William Haiwarde's 1595 map of Marshchapel, showing the saltern mounds still operational in the east at that time and being gradually reclaimed as one moved further from the sea; click here for a larger version of this map.

Lidar map of the same area of Marshchapel, showing the surviving saltern mounds, which matches up remarkably well with the 1595 mapping of Haiwarde. Click here for a larger version of this picture (image: Lidar data © Environment Agency, provided under Open Government Licence; rendering by lab, CC BY 4.0).

Looking south of the Marshchapel area, several more 'islands' can be noted. The first of these relates to the village of Conisholme, to the south-east of Grainthorpe. The name itself makes reference to its origins as an island in the Late Saxon coastal marshes, reflecting Scandinavian kunung + holmr, 'the king's island', and it lies between two branches of the River Lud (the northern outfall being the medieval port of 'Swine' and the southern one being 'Somercotes Haven'). There was clearly some sort of significant settlement activity at Conisholme by the late tenth or early eleventh century, as the head of an Anglo-Scandinavian standing cross of this date depicting Christ in low relief has been found in the churchyard here. Interestingly, Conisholme is still shown as located on a large island between the river outfalls on the Saxton map of 1576 and this situation is made even clearer on the John Speed map of 1611/12 and especially John Cowley's map of c. 1743–5, reproduced below. Both of the latter maps actually show two islands between the two outfalls of the Lud, the larger of which is Conisholme and the smaller, seaward island is probably the area of thirteenth-century storm beach and associated medieval to early modern saltern mounds visible on Lidar and geological maps of the area.

The Outmarsh 'island' of Conisholme on Christopher Saxton's 1576 map of Lincolnshire, showing a large 'island' of land between the northern and southern outfalls of the River Lud (image: British Library).

John Cowley's eighteenth-century map of Lincolnshire, dating from c. 1743–5,  showing a significant estuary for the Lud with two islands in it; the larger of the two is Conisholme and the smaller is probably a raised storm beach with salterns on it, with this still being partly visible on Lidar. 

Finally, there is an intriguing ancient sand island in this area running from North Somercotes to Saltfleet. As was discussed in a previous post, the land in this part of Lincolnshire began to be inundated by the sea from c. 6000 BC, and whereas the flooded landscape of glacial till further south had hills and larger islands of higher ground that remained above high tide right through into the post-Roman era, this was not the case here. Instead, the Mesolithic land surface in this part of Lincolnshire appears to have been completely flooded by c. 3000 BC, aside from one small short-lived island of glacial till at Grainthorpe (which was itself flooded during the following millennium). However, two persistent sand bodies did form here which were of some significance. The most important of these ran from Saltfleet to North Somercotes and seems to have formed during the original flooding of the region, as its base lies directly on the Mesolithic land surface. By c. 3000 BC it would appear to have been entirely surrounded by coastal marshes and the sea, forming an sandy island in the coastal zone that continued to build up and persist into the Anglo-Saxon period. By the medieval period, the areas to the west of this 'island' had largely ceased to be coastal marshes and the ancient sand body was itself subsequently covered by medieval storm beach deposits, thought to be made up of the remains of the offshore coastal barrier islands that were destroyed in the thirteenth century (see further above).

The coastline of north-eastern Lincolnshire and south-eastern Holderness at the start of the first century AD, showing the ancient, persistent sand body between North Somecotes and  Saltfleet and another stretching down from Cleethorpes to the Marshchapel area. The Somercotes body is thought to have remained in place through the Late Roman and Anglo-Saxon eras as a sand 'island' in the coastal zone before being largely buried under storm beaches in the medieval period; the Cleethorpes to Marshchapel sand body looks to have been largely swamped by the Late/post-Roman marine transgression, which covered it over with a thin layer of marine silt (around a metre thick at North Cotes and rather less than this at Marshchapel), to judge from borehole records, with only a few sections of the former sand bank probably being left exposed to the east of Marshchapel (image drawn by C. R. Green, after a map in Berridge & Pattison, 1994, with some modifications). The present-day coastline from approximately Saltfleet in Lincolnshire to Easington in the East Riding of Yorkshire is shown in grey. Note, this map shows the approximate position of the coastline in this period; however, there would also have been an extensive zone of coastal marshes, inter-tidal flats and the like too on the seaward side of this coastline; these are not mapped here, but they clearly saw a significant degree activity in the Roman period.

Geological map of the Conisholme and North Somercotes area, showing the storm beach deposits in purple, thought to be formed from the remains of the offshore barrier islands destroyed in the thirteenth century, surrounded by deposits of marine alluvium in yellow; the Somercotes to Saltfleet sand body largely lies below the medieval storm beach. Note, the separate area of storm beach to the north of Somercotes probably represents the second island between the River Lud outfalls shown on seventeenth- and eighteenth-century maps. Image taken from the BGS Geology of Britain Viewer, licensed under an Open Government Licence 2.0: contains British Geological Survey materials © NERC 2017.


1.     These coastal barrier islands were first suggested by H. H. Swinnerton in 'The post-glacial deposits of the Lincolnshire coast', Quarterly Journal of the Geological Society, 87 (1931), 360–75. See also D. N. Robinson, The Book of the Lincolnshire Seaside (Buckingham, 1981), pp. 13, 17 (map), 20; S. Pawley, Lincolnshire Coastal Villages and the Sea c. 1300–1600: Economy and Society (University of Leicester PhD thesis, 1984), pp. 69–70, 73–5, 80; S. Bennett & N. Bennett (edd.), An Historical Atlas of Lincolnshire (Hull, 1993), p. 8; Institute of Estuarine and Coastal Studies, Humber Estuary & Coast (Hull, 1994), p. 33; H. Fenwick, The Lincolnshire Marsh: Landscape Evolution, Settlement Development and the Salt Industry (University of Hull PhD Thesis, 2007), pp. 54, 160, 174, 181–2, 189, 199, 202, 267, 304; and Natural England, NA 101: Bridlington to Skegness Maritime Natural Area Profile (Sheffield, 2013), pp. 11, 21.

The content of this post and page, including any original illustrations, is Copyright © Caitlin R. Green, 2017, All Rights Reserved, and should not be used without permission.