Climate Change & Coastal Heritage

Project Areas

5 March 2021• Welsh Project Areas

5. St Tudwal’s & The Warren, Abersoch

News Letter

Location Map

St Tudwal’s Islands

The St Tudwal’s Islands (St Tudwal’s East and West) are situated just off of the coast of the Llyn peninsula at Abersoch. Both islands contain archaeological and structural remains that span the early medieval period to the modern day. St Tudwal’s West is most famous for its lighthouse which was built in 1877 at the request of the Parliamentary Lighthouse Committee. St Tudwal’s East is known to have had a monastic settlement upon it with an associated Augustinian priory constructed in 1291. In 2017 CHERISH commissioned an ALS survey for the islands from which archaeological features were able to be mapped and recorded.
Aerial photograph of St Tudwal’s West (foreground) and East (background).
Aerial photograph of St Tudwal’s West (foreground) and East (background).

The Warren, Abersoch

The Warren beach near Abersoch is interesting both for its archaeology and its dynamic natural coastal landscape. Along the beach are the extensive remains of ancient inter-tidal peat and tree stumps along with two post-medieval shipwrecks. Their sandy beach location means that both the peats and shipwrecks are only very occasionally visible when intense storms remove the sand from the foreshore.
Inter-tidal peats can be valuable archive of past environments. Organic material can be dated by radiocarbon dating, and other environmental indicators such as pollen can be extracted to reconstruct vegetation changes through time. We are hoping to use them to uncover important information about sea-level rise in Wales over the last 8,000 years. Preliminary work by CHERISH has already dated tree remnants to determine that they grew in 2 distinct period – the first about 7,700 years ago and the second about 4,200 years ago. Amongst the tree stumps are also the rare remains of hoof prints that may have been created by ancient animals who wandered the landscape in the last 4,000 years.
Ancient animal hoof prints in the peat at The Warren.
Ancient animal hoof prints in the peat at The Warren.
There are also the remains of two likely 19th century shipwrecks on the beach which have been named as the ‘Fosil’ and the ‘Maria’. Recent research undertaken by the project has in fact indicated that both wrecks could relate to any of at least 28 shipwrecks known to have been wrecked in the Abersoch area during the 19th century. Regular visits to the site are undertaken by CHERISH after periods of intense stormy weather to both assess and record the visible remains as well as any changes caused as a result of storms.
Remains of the Fosil wreck on The Warren Beach, Abersoch.
Remains of the Fosil wreck on The Warren Beach, Abersoch.

Why are we working here?

The main threat to this project area is the increasing frequency and severity of storms and their impact upon the culture heritage on the beach. The peats at The Warren were previously unknown prior to CHERISH investigations and limited historical and archaeological research had been carried out for the two shipwreck sites. UAV and terrestrial photogrammetry have been used to record these sites for erosion monitoring as well as further research into both the ship structures and animal footprints on the peats. The collection of 3D ALS data also addressed a previous lack of high-resolution 3D data for the islands. Beyond the project this data will be used to model the impacts of future sea-level rise on the islands and its structural heritage and important sea bird habitat.
Extracting cores from the exposed inter-tidal peat at The Warren.
Extracting cores from the exposed inter-tidal peat at The Warren.

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4 March 2021• Welsh Project Areas

4. Bardsey Island

Location Map

Introduction

Bardsey Island is situated approximately 3km southwest of the tip of the Llyn Peninsula, separated from the mainland by Bardsey Sound. During the Medieval period the island was an important place of pilgrimage with three pilgrimages to Bardsey being viewed as the equivalent as one to Rome. Medieval archaeological and structural remains can be viewed all across the island with the ruined thirteenth century St Mary’s abbey being the most impressive. Visible archaeological remains scattered across the island also indicate human occupation likely extending back earlier than the medieval period. The island has been owned and maintained by the Bardsey Trust since 1979 and is also listed as a Site of Special Scientific Interest (SSSI) as well as being home to several scheduled ancient monuments and buildings.

Digital Elevation Model (DEM) of Bardsey Island.
Digital Elevation Model (DEM) of Bardsey Island.

Mapping the Island’s Archaeology

Work conducted by CHERISH has built upon the important work conducted by Gwynedd Archaeological Trust in their 2014-15 management plan by using ALS and UAV survey to map all visible archaeological monuments on the island in order to improve and expand upon the existing monument records for the island. Historical aerial photography has also been used to compliment these techniques by providing information on archaeological cropmarks.

The eroding section at Henllwyn has also been hand drawn to accurately record eroding archaeological features. This work is important as previous geophysical surveys show this part of the island to contain a density of buried archaeological remains that could relate to a prehistoric cemetery. Several fragments of animal bone have also been extracted from the section. These have been radiocarbon dated to 778-916 AD, possibly related to early farming on the island.

Transcription of archaeological features from the ALS data of Bardsey Island.
Transcription of archaeological features from the ALS data of Bardsey Island.

Why are we working here?

The main objective for the CHERISH Project on Bardsey Island is to enhance existing datasets relating to the island’s archaeology and coastal erosion. Through the use of ALS and UAV survey CHERISH has been able to supplement existing surveys by providing highly accurate and precise positions for the archaeology and eroding coastal edges. 3D data collected for the island (specifically the eroding isthmus) will be used to model the impacts of future coastal erosion of the island and its heritage sites.

The CHERISH team monitoring and recording erosion and archaeology along the Henllwyn eroding isthmus.
The CHERISH team monitoring and recording erosion and archaeology along the Henllwyn eroding isthmus.

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4 March 2021• Irish Project Areas

Ferriters Castle and Promontory Fort, Kerry

News Letter

Location Map

Introduction

The CHERISH site Ferriter’s Castle and Promontory Fort is located on the Ballyferriter Headland, Dingle peninsula in county Kerry. Doon Point (Dún an Fheirtéaraigh) is a long, narrow promontory extending slightly over five hundred metres from north east to south west. This prehistoric fort is one of 95 coastal promontory forts in County Kerry, 42 of which are located on the Dingle peninsula.

Oblique aerial photograph of Bremore in North Couty Dublin, containing several passage tombs and later a 15th Century settlement
Oblique aerial photograph of Bremore in North Couty Dublin, containing several passage tombs and later a 15th Century settlement

Setting

This headland sits directly to the north of the Mesolithic- Neolithic transition period site at Ferriter’s Cove. Along the length of the promontory, narrow inlets of the sea are present in two locations due to softer sediments being carved out from the harder lava beds in these areas. These inlets divide the promontory into two distinct areas. These necks have been anthropogenically utilised and adapted in the construction of the Promontory Fort with a series of banks and ditches, forming an outer and inner set of defences. There are a number of hut sites and archaeological features visible within the boundaries of the fort. In the western section of the fort, there are a number of hut sites being heavily impacted by erosion. In the 15th or 16th century, later reuse of the fort occurred when the Anglo-Norman Ferriter family constructed a castle on the inner bank of the outer defences. This tower house was originally a 4-5 story rectangular tower, occupied by the Ferriter Family until the 17th century.

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4 March 2021• Irish Project Areas

Ballinskelligs, County Kerry

News Letter

Location Map

Introduction

Ballinskelligs Bay is located on the western seaboard of Ireland. Nestled on the south western extent of the Iveragh Peninsula the bay faces outwards towards the vast Atlantic, having once played a pivotal role in Kerry’s monastic landscape. The UNESCO World Heritage Site of Skellig Michael lies off the Ballinskellig coast. The monastery of Skellig Michael was transferred to the west shore at Ballinskelligs in the mid eleventh century due to hazardous conditions on the rock.

The Priory

The priory of the Arroasian Canons of the Order of St Augustine was founded around 1210 and it retained possession of Great Skellig. The priory’s shoreline location has meant it has been the subject of much restoration work by the Office of Public Works. The erosion at the site has been happening since at least the eighteenth century and has resulted in the destruction of several buildings and much of the south east side of the monastery and graveyard. A substantial sea-wall, revetted by groynes, protects the site. The priory comprises a number of buildings which exhibit architectural details relating to various periods between the thirteenth and fifteenth centuries. The priory was disbanded by 1578. An ancient hamlet is located approximately a 120 metres to the north west of Ballinskelligs Priory, just beyond the northern extent of the OPW seawall. This area is being effected by erosion, that may be attributed to the hard defences in the area.

McCarthy’s Castle

McCarthy’s castle is located to the north of the Abbey sitting on the tip of a narrow promontory of land that juts into the sea. This tower house is probably 16th century in date and associated with the McCarthy’s who were chieftains in Cork and Kerry. The promontory suffers badly from erosion and has changed substantially in living memory, some of this change is often attributed to the 20th century construction of the concrete pier that lies at the end of the Promontory. The castle ruins remain largely intact; however, the southern corner is badly damaged with a breakthrough in the wall in this area. This is partly due to exposure to the sea and the wall being thinner due to the mural stairs located in this corner of the tower house. The land around the castle is impacted by erosion. Excavations were undertaken at the castle in 1988 and 1991 by John Sheehan, University College Cork. Two external lean-to structures with pitched-cobble floors identified during excavation and post-dating the primary period of occupation of the castle are believed to have been a fish curling station. It is recorded that Sir William Petty established a fishery at Ballinskelligs.

The dated tree stump from Inny strand tells how a Bronze Age forest was present in the north of the bay, the continuation of buried peats past the present low water mark indicate the forest covered the area that denotes the intertidal zone today. The basal dates of the peat cores around the Bay inform of the formation dates and phases of the wetlands that now encompass Ballinskelligs Bay. These peat cores will provide further insights into the environmental and climate records for the Bay since the Neolithic Period. The palaeo-environmental evidence when considered in context of the pattern of change recorded due to geological processes around the bay since at least the mid-18th century and in context of predicted climate change impacts due to atmospheric change such as rising sea level indicates a continual loss of the coastal margin into the future as the predominate forces at play continue to enlarge the bay here at Ballinskelligs.

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3 March 2021• Welsh Project Areas

3. Rhosneigr, Llyn Coron, Dinas Dinlle & Morfa Dinlle

News Letter

Location Map

Introduction

Welsh project area 3 encompasses a hugely diverse range of natural environments and heritage sites which are vulnerable to the impacts of climate change which include erosion and sea-level rise. The archaeological and palaeoenvironmental investigations undertaken by CHERISH within this area include coring of lakes to reconstruct millennial-scale environmental change, dating of sand movement events, seabed scanning, intertidal wreck surveying, and the excavation of an eroding prehistoric coastal fort. Archaeological evidence demonstrates that people have roamed and occupied this stretch of coastline for thousands of years. However, CHERISH is uncovering the dynamism of the coastal environment that has shaped not only the coastline but the lives of its inhabitants through combined palaeoenvironmental and archaeological investigations.

Rhosneigr

Aerial image of Llyn Maelog beneath the coastal village of Rhosneigr.
Aerial image of Llyn Maelog beneath the coastal village of Rhosneigr.

Rhosneigr is a small village occupying a bedrock outcrop on the southwest coast of Anglesey. Below the village is a 20 hectare lake known as Llyn Maelog which is separated from the beach by a 500m-wide sand-dune complex. The dunes rise to a height of about 20 metres immediately behind the beach Traeth Llydan. The lake is a significant ecological habitat for a range of plants, birds and animals, but  is also an important focal point for residents and tourists alike. It is surrounded by a diverse range of important archaeological sites such as burial tombs, settlement sites, and the site where 180 iron and copper alloy objects were discovered. Therefore, it seems likely that this substantial freshwater lake would have been a significant site in the past.

CHERISH has recovered cores of lake sediment in order to reconstruct the evolution of the lake and its surrounding environment. Pollen analysis has been carried out to reconstruct the major vegetation changes at the site, and organic material radiocarbon dated to provide a robust timeframe. Diatom analysis has also been employed by CHERISH to reconstruct how the lake itself has changed. Diatoms are microscopic algae that live in virtually every water type, and like any plant, different species have their own habitat preferences. They are sensitive to physical and chemical changes and thus are really useful to determine how a lake may have changed through time. The sediments of Llyn Maelog indicate that it formed at the end of the last glacial episode and that it was inundated by the sea approximately 7000 years ago changing it to a marine environment perhaps for a few hundred years. This makes it an important site in the context of past Welsh sea-level change, but also illustrates how future sea-level rise may impact coastal communities and the natural environment.

Llyn Coron

Llyn Coron is a 30-hectare lake impounded by the Aberffraw dune system, about 5 km southwest of Llyn Maelog. The lake was thought to have developed in the medieval period, which documentary evidence suggests was a particularly stormy period in the region. It is believed that as the sand dunes developed, they blocked the River Ffraw creating a natural dam and the lake formed behind them. The dune system covers about 360 hectares and together with the lake forms part of a Special Area of Conservation and Site of Special Scientific Interest.

The CHERISH team preparing to core Llyn Coron.
The CHERISH team preparing to core Llyn Coron.

CHERISH is investigating the lake sediments to see if they contain a record of storminess that can be used to identify changes in past weather patterns. We are using chemical elements such as bromine and the physical presence of sand grains to reconstruct changes in storm intensity or frequency. We are combining these techniques with OSL dating to date layers of sand and provide a chronology for the core. We are also looking at how different species of diatom (microscopic algae found in all waterbodies) responded to the lakes evolution. Diatoms are sensitive to light, pH, salinity and the nutrient status of their environment, which makes them good indicators of

Dinas Dinlle & Morfa Dinlle

The gravel ridge and dune system of Morfa Dinlle situated at the southern entrance to the Menai Strait.
The gravel ridge and dune system of Morfa Dinlle situated at the southern entrance to the Menai Strait.

Situated at south-western entry to the Menai Strait is Morfa Dinlle which is the largest active gravel beach ridge system in Britain. It comprises a series of linear ridges (some over a kilometre in length), which have accumulated in a north-westerly direction. The central section also contains a large sand-dune complex which combine with the gravel ridges to form an important and fragile coastal ecosystem supporting many rare fauna and flora. Previous research suggests that the ridge system has developed over the last 2000 years, but the exact rate of the spit growth has not been established. It is also unclear how future sea-level rise may affect its development. CHERISH is aiming to provide a detailed chronology for the evolution of the spit to better understand the formation process and coastal sediment transport.

About 3 km to the south of Morfa Dinlle is the heavily eroded prehistoric coastal fort of Dinas Dinlle. The site is situated upon a glacial moraine, which has been sculpted and modified by people in the distant past to create a formidable series of defences. The western elevation is being actively eroded by climatic and coastal processes, resulting in the loss of the western rampart which likely completely enclosed the settlement in the past. Geophysical surveys and excavations of Dinas Dinlle by CHERISH have uncovered evidence of a substantial settlement site within the fortifications, most notably the discovery of a stone-built roundhouse which is 13 metres in diameter – the largest of its type known in Wales. Archaeological finds indicate occupation during the Romano-British period but it is likely that it was constructed during the Iron Age period. Whilst the structures themselves are extremely impressive and important, the fact that they are entombed in vast quantities of wind-blown sand is perhaps more intriguing. Although we cannot be certain, it is possible that the fort was eventually abandoned due to sand inundating the site. The scale of sand deposition emphasises the power and hazards associated with the natural coastal environment and its ability to impact the communities that occupy and utilise the coastal zone.

Aerial image of the prehistoric coastal fort of Dinas Dinlle.
Aerial image of the prehistoric coastal fort of Dinas Dinlle.

CHERISH is using Optical Stimulated Luminescence (OSL) dating on the sand deposits that overlay the roundhouse, together with samples from the eroding cliff face and the dunes at Morfa Dinlle to determine when these sand deposits were laid down. We hope this technique will provide a robust chronology for the sites themselves, but we are also trying to reconstruct a regional picture of coastal environmental changes investigating other sites in the area. CHERISH also hopes to provide a palaeoenvironmental context for human occupation of the fort.

Why are we working here?

The coastal landscape within project area 3 represents some of the most dynamic and sensitive coastal environments in Wales. The multidisciplinary CHERISH team is well-suited to researching these challenging environments. By combining methods commonly used by archaeologists and earth scientists, the project has begun to reveal how these coastal environments were shaped by the changing climate over the last 12,000 years. This work is also important in unravelling how humans who inhabited this part of Wales would have been affected by and responded to environmental change. Uncovering past coastal environmental changes not only gives us an interesting insight into the past but also provides an insight to how these landscapes may change in the future.
Members of the CHERISH team recording the exposed eroding cliff face at Dinas Dinlle.
Members of the CHERISH team recording the exposed eroding cliff face at Dinas Dinlle.

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