Deposits on upland hillslopes are formed by a range of processes like debris flows, rock falls, slope wash and soil creep. The movement of sediment by these processes occurs over days, years or decades and can have far-reaching implications. Over geological timescales it can influence the relief of mountain ranges, but on human timescales it is also a potential geohazard affecting roads, bridges, and reservoirs, and a key factor in managing river habitats and water quality.  

Faults are important geological features, even when they are no longer active tectonic structures. They are often associated with highly fractured ‘damage zones’ that are relatively weak, providing abundant source material for slope processes and acting as conduits for groundwater flow. We investigated how faults control the types of deposits that are produced on upland slopes by weathering and erosion, and how the direction of a fault intersection with a hillside influences the way sediment is mobilised and transported to rivers and reservoirs.  

Study area: Tweedsmuir Hills, Scotland

In the Tweedsmuir Hills, in Scotland Southern Uplands, the rolling upland landscape is bisected by a series of brittle faults comprising highly fractured damage zones in the otherwise hard, metasedimentary rocks. The study area, at the head of the Talla Reservoir, provides a prime opportunity to compare the geomorphological imprint of slope-oblique faults that traverse across a slope at a low angle (roughly perpendicular to the slope direction) with that of slope-parallel faults (roughly parallel to the slope direction).  

Faults that traverse slopes at low angles are associated with enhanced regolith (weathered bedrock) production, which forms a more-or less continuous spread of colluvial deposits (loose sediments that move downslope under gravity) across the slope. Sediment transfer to the valley floor is limited because topographical breaks associated with the slope-crossing structures disrupt gully systems and inhibit sediment ‘flow’ downslope.

By contrast, slope-parallel faults are associated with more focused erosion along fault zones, giving rise to a deep and well-connected gully system. The alignment of slope and fault directions creates positive feedback, which enhances downslope erosion and transport to the valley floor. This feedback has resulted in approximately 20 times more rock being eroded per metre of fault length than in the slope-oblique fault system. 

Influence on infrastructure design

The movement of sediment is associated with geohazards such as debris flows and rock falls as well as slope instability that can damage upland transport, energy and water infrastructure. However, sediment movement on slopes is a natural part of how our landscape behaves and interrupting or altering the flow of sediment from hillslopes into streams can affect river environments and habitats, and influence water quality in reservoirs.

Understanding the mechanisms of active slope processes and their distributions within the landscape is necessary to ensure we can design effective approaches for managing both the impact of moving sediment on our built infrastructure, and the effect this infrastructure has on our rivers and reservoirs.

Another way of looking at it is that every slope has its own story. Our work in Talla demonstrates how geomorphological mapping and quantitative field analysis can be used to help understand the dynamics of slope systems, adding to our knowledge of the ‘language’ of slopes. By understanding how their past geological history influences their present processes, we can learn to better ‘read’ slopes and ensure we develop more positive relationships with them.

About the authors

Reference

Whitbread, K, Thomas, C, and Finlayson, A. 2023. The influence of bedrock faulting and fracturing on sediment availability and Quaternary slope systems, Talla, Southern Uplands, Scotland, UK. Proceedings of Geologists’ Association, in press. DOI: https://doi.org/10.1016/j.pgeola.2023.11.003

Loch Lomond is a freshwater lake at the heart of the Loch Lomond and Trossachs National Park in the south-west highlands of Scotland. It is surrounded by beautiful landscapes and vistas influenced by past ice ages.  

Using seismic data, marine geoscientists at BGS have discovered a new sedimentary unit buried in deposits beneath the loch, giving new insights into its past glacial history.

Scotland in the last ice age

Much of the highlands of Scotland were covered by an extensive mountain ice cap 12 900 to 11 700 years ago, during the last period of cold climate (known as the Younger Dryas or the Loch Lomond Stadial). Decades of onshore research have shown how past ice ages have shaped the landscape of Loch Lomond, including carving of the present-day loch itself and its surroundings through processes such as erosion and deposition. However, this new dataset provides an interpretation of the stratigraphy now buried beneath the loch.

Mapping the loch bed and subsurface features

51ÁÔÆæ used multibeam bathymetry surveys to gather detailed information about the features on the loch bed. The data revealed a series of flat-topped and prograding features (or the growth of a river delta further out into the sea over time) and ancient glacial geomorphological features. These features include drumlins, which are oval-shaped hills largely composed of glacial drift that form parallel to the direction of ice flow, and streamlined bedrock, created by glacial restructuring of hard beds that produces a collection of extended rock landforms, interpreted as showing the direction of the palaeo-ice advance.

It been incredibly exciting to have had the opportunity to interpret these datasets and present the loch surface and subsurface in a way we’ve never seen before. The seismic mapping and interpretation of the Inchmurrin Formation helps us understand past landscapes and geological events that are now buried under the loch bed. We are keen to undertake further research in and around the area, building on the seismostratigraphical framework that we observe in Loch Lomond.

Nicola Dakin, BGS marine geoscientist.

51ÁÔÆæ geoscientists used seismic data to map the subsurface of the loch. Seismic data uses sound waves, which travel through buried layers of sediment, forming an acoustic image based on density variations between different sediment types. We interpreted the acoustic signature, linking sedimentary processes and depositional environments to past climatic cycles. This provided a framework to create an updated chronostratigraphy within the loch.

What did the survey reveal?

• during glacier advance associated with the cold Younger Dryas climate, glacial landforms were shaped underneath the ice; these can now be identified at the base of the sedimentary succession, up to 60 m below the loch bed surface
• as the ice retreated, vast volumes of water and sediment were released into the loch, leaving a sequence of layered sediments up to 44 m thick
• immediately after deglaciation of the area, exposure of steep loch margins likely resulted in landslides into the loch, producing a unit that is shown as a transparent layer in the seismic data and can represent up to 50 per cent of the sediment fill in places — we have named this new unit the ‘Inchmurrin Formation’
• as the climate transitioned from the early Holocene to the present day, a final phase of lacustrine sedimentation followed, depositing up to 127 m of the youngest, layered, grey-brown lake sediments

Global value of this work

Work is continuing to build understanding of other lochs in the area. The Loch Lomond dataset is a valuable resource that could enable BGS to offer insights into the extent and rates of landscape adjustment that accompanied the transition from glacial to non-glacial conditions. Such findings are of global importance when considering landscape stability and potential future geohazards in regions that are undergoing rapid deglaciation, such as around the European Alps, Himalayas and New Zealand Southern Alps.

About the author

In July 2022, the BGS Hazard Products team visited Yorkshire to assess some key geological hazards. The trip was an opportunity for the team to gain insight into the natural processes and geological features that underpin many of the digital data products they develop.

The team has a diverse skill set, from expertise in Python coding and GIS analysis to engaging with stakeholders and developing business relationships with partners and clients. This melting pot of skills allowed the team to consider geological hazards and potential solutions from a unique perspective and prompted useful discussions around translating BGS science into user-oriented digital hazard solutions as well as the quality and availability of input data.

The team spent two days in the field studying a range of geological hazards in action and considered the strengths and limitations of existing BGS geohazard data products to determine areas for future development.

Sutton Bank

Sutton Bank is a near-vertical, around 140 m-high cliff in Jurassic strata representing about 60 million years of geological time. During the last ice age, about 20 thousand years ago, a lobe of ice extended southwards in this lowland area between the North York Moors and the Pennines. As the ice flowed along the western edge of the moors, it gouged out the soft underlying rocks of the Lower Jurassic, leaving the escarpment you see today.

The clifftop panorama showcases a complex lowland landscape underlain by a mixture of superficial deposits and bedrock. As the ice melted and retreated, it deposited till and outwash deposits, which shaped the landscape we see from the viewpoint today. For example, Gormire Lake, located just below the escarpment at Sutton Bank, formed as a result of glacial deposits blocking drainage channels and trapping water behind them.

is situated at the top of the escarpment, with parking, visitor centre, toilets and café. A short walk leads to a viewpoint with a panoramic view across the previously glaciated vale.

This location was really useful to visualise the landscape of the area and understand how glacial periods in Earth history had imprinted on this landscape. It provided useful context for the field sites to come.

Jenny Richardson.

Relevant data products

• 51ÁÔÆæ Geology
• GeoSure
• Superficial Deposit Thickness Model
• 51ÁÔÆæ Civils

Sneck Yate

Continuing northwards along Cleveland Road from the visitors centre we reach Sneck Yate. Parking is located in a small gravel layby from where it is a short walk over the top of the escarpment to view cambering features.

The geology at this location comprises the same Jurassic strata as the previous site and this sequence of the and the overlying the softer has created a geohazard called cambering.

Cambering involves large-scale stretching, tilting or rotation of more competent blocks of rock over less competent strata, in this case the Oxford Clay Formation. This tilting can result in discontinuities known as gulls opening up parallel to the valley axis, which can range in width from millimetres to tens of metres and may be sediment filled or not even propagate to the surface.

Cambering and associated features such as gulls and valley bulging are all responses to stress relief or ‘unloading’, which results from rapid incision or erosion of the landscape in conjunction with gravitational forces. It is often associated with glacial erosion and retreat.

This site helps us to better understand the processes associated with permafrost, Quaternary conditions and rates of landscape evolution. Improved understanding also informs planning for ground engineering projects.

• More detailed explanation of cambering and associated geological features 

The size and scale of these features can impact significantly on engineering projects, for example, evaluation of clay disturbance as a consequence of valley bulging was critical to the construction of the Empingham dam at Rutland Water and the upper dams of the Derwent Valley. Cambering is not explicitly defined in our current data products and visiting this site prompted useful discussions on the feasibility to improve this.

Russell Lawley.

Relevant data products

• 51ÁÔÆæ Geology

Hawnby

From the top of the escarpment the team dropped down into Hawnby village. En route, we noted the steep slopes and landslide events associated with particular geological horizons. Here, an impermeable clay layer forces groundwater to the surface where it emerges as springs and in several cases has initiated landslides in the overlying superficial deposits.

Hawnby lies in Rye Dale on the northern bank of the River Rye. River erosion, flooding and water availability can all be considered risks here. The bridge at Hawnby forms a narrow pinch-point in the valley and carries key utilities infrastructure over the River Rye. From 19 to 20 June 2005 there was a major storm event and flooding devastated the area. Damage included the complete destruction of the bridge, removing access to the village and further impacting the community through the loss of utilities.

It is particularly important to understand the geological constraints and potential for flood events, especially in changing climate conditions where storms are more likely to become more frequent and more intense. When the bridge was rebuilt, design improvements were made to allow water to flow across the bridge and road in an effort to prevent the constriction of river flow and associated erosion in future flood events.

Understanding the capacity of the floodplain, the erosion potential of the sediments and the additional influences such as extra water input into the system from springs can hugely help catchment planning and effective adaptation.

Henry Holbrook.

Relevant data products

• GeoScour
• GeoSure

Holbeck Hall, Scarborough

South of Scarborough is the site of the former Holbeck Hall Hotel, which was destroyed by a landslide between 3 and 5 June 1993.

The Holbeck Hall site is underlain by till deposits overlying the at the top of the cliff, with the cropping out on the foreshore and creating a wave-cut platform. This rotational landslide involving about one million tonnes of glacial till cut back the 60 m-high cliff and flowed out across the beach to form a semicircular promontory 200 m wide projecting 135 m outward from the foot of the cliff. This was rotational landslide that degraded to a mud or debris flow and covered the rocks of the wave-cut platform.

The first signs of movement on the cliff were seen six weeks before the main failure, when cracks developed in the tarmac surface of footpaths running across the cliffs.

• More details of the Holbeck Hall landslide

The likely cause of the landslide was a combination of:

• intense rainfall in the prior two months
• poor drainage of the slope
• high pore-water pressure in the slope
• susceptible superficial geology

Coastal defences have since been installed to protect the toe of the slope from further erosion and pore waters are monitored regularly.

We have been investigating using remote sensing terrain data to identify historic coastal mass movement deposits and it was helpful to observe the form and terrain characteristics of this large scale landslide. Landslide morphology is especially complex at the coast where wave action is also an issue.

Sophie Taylor.

Relevant data products

• GeoCoast
• GeoSure landslides
• 51ÁÔÆæ Civils

Danes Dyke, near Flamborough

Danes Dyke lies on the southern coast of the Flamborough Head peninsula. It consists of a deep, wooded valley running north–south towards the coast.

The steep ravine is a palaeo-valley about 150 m wide and filled with a complex succession of periglacial, glacial and aeolian sediments. The chalk is folded and faulted with structures visible in the foreshore at low tide. Periglacial weathering was likely focused here due to the presence of faults and evidence for periglacial fractured chalk and rubbly chalk gravel can be seen in the cliffs at the mouth of the ravine. These gravels are overlain by till deposited by a North Sea lobe of the last British–Irish ice sheet that emanated from the Grampian Highlands of Scotland and flowed southwards over which is now the floor of the North Sea.

It is important to understand the nature of the boundary between the chalk bedrock and overlying superficial deposits as well as the properties of the different lithologies. Fracturing and weathering also cause weaknesses in the rock, making them more susceptible to failure.

The typically uneven boundary between chalk and till, differential rates of weathering, and chalk dissolution can have impacts on building foundation design, underground utilities and infrastructure projects. Where these features occur inland, they’re often unseen, so being able to visualise this boundary and erosion features at the coast is a helpful exercise when considering measures to mitigate against associated issues

Clive Cartwright.

Relevant data products

• Superficial Deposit Thickness Model
• GeoSure soluble rocks
• 51ÁÔÆæ Geology
• GeoCoast

In early September 2022, eight geologists from different disciplines across BGS completed the applied glacial geology field-based training course in north Norfolk, led by BGS Emrys Phillips and Jonathan Lee. The course benefits geoscientists working on applied projects where glacial geology will affect ground conditions and properties of the shallow subsurface, such as offshore windfarms.

During the course we visited Sheringham, West and East Runton, Happisburgh and Weybourne. We were able to develop skills to describe and interpret glacial sediments and deformed materials, and their influence on ground conditions both on and offshore.

Day 1: Happisburgh and Weybourne

On the first training day, we drove to Happisburgh. We were lucky with the weather not only on the first day but also throughout the field course. With a beautiful sea view, Emrys and Jon introduced us to the topic of glacial geology and explained the history of coastal erosion at the site. At Happisburgh, we examined several cliff sections through the , the Ostend Clay Member and the .

In the afternoon we drove up the coast to Weybourne, where we encountered the , which overlies bedrock. The shallow marine sands and gravels of the Wroxham Crag directly overlie a brecciated chalk unit, which exhibits evidence of periglacial features such as frost heave, soft-sediment deformation and hydrofracturing.

Day 2: East Runton and the West Runton Mammoth

On Day 2, we visited East Runton, where we learned more about glacitectonic chalk rafts (massive blocks of glacially displaced chalk bedrock), their direction of emplacement and the development of ice-marginal sand basins. We also examined the preglacial deposits that are exposed to the east of West Runton, including the Wroxham Crag Formation (shallow marine) and the West Runton Freshwater Bed, which is an organic deposit. Since the 19th century, the latter has become well-renowned with amateur and professional fossil collectors, because it yields both floral and faunal fossil remains and provides much information on the climate and environment during a preglacial interglacial period. The remains of the world-famous West Runton Mammoth were also discovered at the site in the early 1990s.

Day 3: West Runton

On the third day, we visited the coastal section to the west of West Runton, where we continued to learn about chalk raft emplacement and preglacial and glacial stratigraphy and started to think about how glaciers interact with sediments beneath and in front of them. Cliff sections at West Runton record the transition from proglacial through ice-marginal to subglacial environments, which produces distinctive styles of sedimentation and deformation. We also compared the resultant glacitectonic mélange and structure to interpreted seismic cross-sections from the Dogger Bank area of the North Sea, which shows similar features offshore.

Day 4: Sheringham and Skelding Hill

Our fourth and final day started off dry and bright as we started with an ascent of Skelding Hill, which offers a stunning panoramic viewpoint of the coastline between Cromer and Weybourne. From our vantage point, we were able to get a better view of the geomorphology of the area, helping us piece together the broader glacial history.

We then walked down the hill to the beach, where we found some natural beach analogues in the sand that we were able to relate to the glacial activity, including a miniature braided river system.

We walked along the coast to the see the cliff face directly under the summit of Skelding Hill. Here we split into teams and were set challenges to describe the structural geology, geomorphology and unitisation of the glacial sediments we could see in the cliff face.

In the afternoon, we had to dodge several very dramatic-looking rainstorms. However, they quickly passed and this meant members of the team could enjoy a quick pasty and cake in one of Sheringham local bakeries. At the end of the day, Jon and Emrys provided a summary of the week and presented a geological model for the history and direction of glaciation in north Norfolk. All members of the team thoroughly enjoyed the trip and look forward to applying our new skills going forward!

This course was one of many scientific and technical support activities funded and organised by BGS Learning and Development.

About the authors

A paper marking the culmination of a highly successful project into a former ice sheet is helping researchers to understand more about the north-west European continental shelf. It’s also helping improve forecasting for the Antarctic and Greenland ice sheets.

The five-year, £3.7 million BRITICE-CHRONO consortium, funded by NERC, took on the most ambitious geochronological project yet, encompassing on- and offshore mapping around the UK and Ireland to better describe and understand the growth and decay of the last British–Irish ice sheet.

BRITICE research included 1500 days of field investigation yielding 18 000 km of marine geophysical data, 377 cores of sea-floor sediment and geomorphological and stratigraphical information at over one hundred sites on land. This enabled the generation of 690 new geochronometric ages, which were collected to understand the timings, coverage and retreat of the British–Irish ice sheet and to provide a geochronological framework between 31 000 and 15 000 years ago.

The findings bear a strong similarity to the dynamics and evolving configuration in the Antarctic today, enabling scientists to refine and improve current ice sheet modelling approaches. It will also aid researchers investigating regional palaeoenvironments as well as those working on offshore development (e.g. offshore renewables) and marine management.

51ÁÔÆæ is proud to have played a role in this important project. The paper compiles and distils many of the detailed findings from the onshore work and offshore transects of the project and will serve as a useful resource to inform and expand on current knowledge on the evolution of the British–Irish ice sheet.

Dayton Dove, BGS Marine Geoscientist.

51ÁÔÆæ scientists participated in and contributed to the project by providing expertise, data and information to support planning, implementation and interpretation of survey and project results. The offshore coring was also carried out by BGS engineering teams.

Two reconstructions of the ice sheet were developed: an empirical version and one that combines modelling and the new empirical evidence. Palaeoglaciological maps of ice extent, thickness, velocity and flow geometry at thousand-year time intervals were also produced.

The paper, , was published in BOREAS.

The adrenalin, the attacks, the climbs, sprints, chases and, for some, the incredible victories, would arguably not be such a spectacle were it not for Britain incredibly diverse geology.

Though the link is rarely made, the geology beneath our feet is ultimately responsible for shaping our landscape today, even shaping our Strava segments.

Our rich variety of landscapes, largely consisting of Triassic, Jurassic, Cretaceous and Tertiary strata, has paved the way to victory for the world greatest cyclists across mountains, countryside and coastline for decades.

This year edition in 2022 is set to be no different, with eight days of racing from the iconic ‘granite city’ of Aberdeen in Scotland to the distinctive chalk stacks of the Needles on the Isle of Wight. 

But why are some stages of this year Tour hillier than others? It ultimately determined by the rocks and sediments of an area and the subsequent geological processes that have been eroding, folding or faulting them over the hundreds of millions of years since they were deposited.

Here we take a closer look at some of the rocks behind the race.   

The materials that make a bike

It not only our landscapes that are influenced by geological processes; our equipment is too. Since lightweight carbon fibre began to dominate the performance cycling world nearly two decades ago, races like the Tour of Britain have featured even lighter, stiffer and more impressive bikes and designs. 

Many of the components found on a racing bike require materials derived from the ground beneath our feet. In case you’re wondering, here are the basic materials required and some are more obscure than you might think:

So if, like us, you’re thinking about exploring Britain fascinating geological wonders on a bike, why not take a moment to appreciate the world beneath your wheels and the geological conditions that influence your next cycling adventure.