Tynemouth headland: an example of coastal landsliding and rockfall processes

Helen Reeves, Claire Dashwood and Pete Hobbs carrying out a laser scan survey of the north-facing cliffs of the Pen Bal Crag headland from the Short Sands beach in King Edward’s Bay, Tynemouth.

The geology of Tynemouth area is a mix of strong rocks and formations that are less resilient to constant attack from the sea.

Several defences have been constructed and these need maintenance and repair to preserve this rocky headland.

Various processes affect the stability of the Pen Bal Crag headland and the coastline of King Edward’s Bay and a range of landslide types can be observed.

The BGS uses a LiDAR laser scanner to scan the cliffs and provide valuable assistance in assessing the instability processes that affect these sites.

Geology

A coloured 3D point cloud, an output from the terrestrial laser scanning, of the north-facing cliffs of the Pen Bal Crag headland; taken from the Short Sands beach in King Edward’s Bay, Tynemouth.

The geology at Tynemouth comprises mainly Permian and Carboniferous bedrock.

The Permian bedrock consists of the Raisby Formation dolostone (magnesium limestone; blue) and the Yellow Sands Formation sandstone (orange).

In turn this overlies Carboniferous sandstone (green) followed by a series of relatively weak mudstone, siltstone and sandstone (grey) of the Pennine Middle Coal Measures.

Cutting through these bedrock materials is a micro-gabbro dyke (an intrusion of Igneous rock), probably formed during the Palaeogene. Thick glacial till deposits (Devensian) overlie these bedrock materials, with the exception of the Permian bedrock headland which is free of till.

This area forms the southern part of the Site of Special Scientific Interest (SSSI) that stretches from Tynemouth to Seaton Sluice.

Tynemouth Landslide Superficial Map Key
Tynemouth Landslide Geology Map Key

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Tynemouth Castle headland: Pen Bal Crag and King Edward’s Bay

The geology of Tynemouth has had a profound effect on its history; a strong and resilient igneous micro-gabbro dyke provided a natural pier jutting out to sea and protecting the northern coastline of the Tyne estuary.

Local dolostone and sandstone were sufficiently resistant to form a prominent rocky headland, known as Pen Bal Crag, to the north of the dyke.

This special location led to the foundation of a priory, early in the 7th century.

In the subsequent centuries the early Northumbrian kings were buried here. However, a long period of ransacking and rebuilding ensued.

Late in the 13th century the fortifications of the priory became more substantial and much of the remains can still be observed today.

Slope instability

Various processes affect the stability of the Pen Bal Crag headland and the coastline of King Edward’s Bay and a range of landslide types can be observed.

Rockfalls mainly occur along the headland while in the King Edward’s Bay landsliding is often complex and involves falls, slides and flows.

English Heritage looks after the site and has engaged in several phases of stabilising the cliffs, including maintenance of the concrete arches that were first constructed more than 100 years ago.

A large cavity, measuring 4 m, was found behind the concrete arches requiring casting of a large concrete base, anchored into the bedrock.

The wet summer of 2012 has resulted in an increased activity of landsliding across the nation and King Edward’s Bay has also experienced increased activity during this period.

Landsliding at the Bay involves local rock (fragments of dolostones and sandstones), but most of the slide material is dark grey in colour and probably involves fill material sliding over a stable bedrock surface.

The upper slopes, comprising Permian bedrock, have been stabilised using mesh and rock bolts.

Monitoring of unstable slopes: Pen Bal Crag and King Edward’s Bay

The locations from where the terrestrial laser scans were taken from Short Sands beach in King Edward’s Bay and from the North Pier

The BGS have carried out LiDAR (laser scan surveys) of the headland and the bay. These scans provide valuable assistance in assessing the instability processes that affect these sites.

Multiple scans, taken over a period of time, allow comparative analyses that help build up a picture of the coastal changes that are occurring.

Tynemouth headland landslides gallery

Contact the Landslide Response Team

British Geological Survey
Keyworth
Nottingham
NG12 5GG
E-mail: Landslides team
Telephone: 0115 936 3143
Fax: 0115 936 3276