A Geology Field Trip at Ilkley Moor

 

A view down Backstone Beck

When undertaking the recce of Ilkley Moor for the Sheffield U3A Geology Group field trip in August 2024, in the company of John and Trish, we were unable to locate Lanshaw Delves and, as a consequence, we did not get to see the sites 16-21 in the Ilkley Moor - Its Geology and Heritage geological trail by Gareth Martin and David Leather. 

 

The route of the geological trail 

 

With Ilkley Moor being too far away from Sheffield to undertake another recce, I decided that our field trip should concentrate on the sites around the Cow and Calf and Hangingstone Quarries, before further exploring Backstone Beck and Rocky Valley and then returning to the Cow and Calf car park via White Wells and Cowpasture Road. 

 

The revised route

On a very unseasonably cold day in August, 11 of us turned out along with Stephanie, a resident of nearby Addingham who had seen my photos of the recce on Facebook and had expressed an interest in joining us to learn more about the local geology. Meeting at the Cow and Calf car park, we then proceeded to the first locality, where a fossil mould of Knorria - the inner pithy layer of a Lepidodendron club moss - proved to be of great interest to the group members who had attended the field trip at Otley Chevin. 

 

The Knorria fossil

 

Continuing to the Calf, legend has it that it was detached from the Cow by the giant Rombald, who clumsily broke it off while running away from his enemy, his wife, before she dropped her skirtful of stones nearby during a fight with him, but the reality is that it was detached from the Cow by the glacier that flowed along Lower Wharfedale during the Pleistocene Epoch. 

 

Approaching the Calf

We looked for graded bedding in the pebbly gritstone, to prove that the large block had rotated 140 degrees, and evidence of that it was once attached to the main outcrop - the western side has a very flat surface that matches the nearby rock face on the Cow. John, who undertook the recce with Trish and I, then explained that the lyrics to the unofficial Yorkshire Anthem On Ilkla Moor Baht 'at were composed here by a church choir on an outing to Ilkley Moor. 

 

The field trip report for Ilkley Moor

 

Moving on to the entrance of the Cow and Calf Quarry, we had a quick look at various ripple marks that show the direction of current flow and a section of supposed tidal laminites, which we had seen at Otley Chevin. When studying the massive gritstone in the quarry faces, Stephanie - a rock climber herself - thought that the elaborate graffiti marks the climbing routes. As usual, when leading field trips, I didn’t get much opportunity to take photos and have relied on those taken of these locations by group members and used in my field trip report. 

 

A view from the path to the top of the Cow and Calf Quarry

 

Briefly stopping to take in the view beyond Ilkley, we then headed to the top of Cow and Calf Quarry and were all very surprised to discover that over an altitude of only 10 m, there was a considerable change in the force of the wind that was blowing from the south - from a light to a moderate breeze, as described by the Beaufort Scale.

 

Discussing the colonising of the ice scoured gritstone by heather

 

After having a good look at the Victorian graffiti at the Cow and Calf Rocks, we discussed the glacial history of Lower Wharfedale and Paul described the colonisation of the ice scoured rock by heather, which I emphasised had been helped by the disintegration of the feldspar in the gritstone to provide nutrients in the very thin siliceous soil. 

Exploring the Cow and Calf Rocks

With the wind still blowing strongly, we found a sheltered place in the woods below the escarpment to have our lunch, before commencing our afternoon walk by investigating the cup and ring marks above Hangingstones Quarry. 

 

Investigating the cup and ring marks above Hangingstones Quarry

 

This area, particularly Rombalds Moor to the east, has hundreds of rock carvings that date from the Neolithic to the early Bronze Age (c.4000-1500 BC) and the Victorian graffiti records Ilkley’s prosperity as a spa town, but other modern graffiti such as the Celtic cross can also be seen – which unfortunately includes very crude lettering that has no aesthetic value. 

 

A modern Celtic cross

 

Moving on to the slickensides in the south-west corner of Hangingstones Quarry, where the effects of movement along faults was highlighted, we continued to the glacial striations above it and carried on our discussion about glaciation and its effects on the rocks and landscape. 

 

The location of the glacial striations above the Hangingstones Quarry

 

Following one of the paths to Backstone Beck, the views to the west provided our first encounter with the large rotational landslide that covers much of the lower slopes and is characterised by very uneven ground upon which bracken has taken hold. 

 

A general discussion of the surrounding landscape

 

Carrying on down the path and heading up to the location of the waterfall and knickpoint, we stopped to examine the glacial till that is exposed in a couple of places on the east side of the valley, where the covering of heather has been eroded away. 

 

An exposure of glacial till at Backstone Beck

 

During the recce, we had not actually stopped to look at these exposures and I had to call John, who was leading the group along the path at this point, to come back with them and have a good look. Taking care not to lose my footing on the steep ground, I wanted to try and obtain a piece of Carboniferous Limestone, which would provide evidence that the glacier had flowed down Upper Wharfedale to the north, but I could not get close enough to the exposure. 

 

A detail of the glacial till at Backstone Beck

Reaching the point where the public footpath from the Cow and Calf Rocks crosses Backstone Beck, which here flows along a small shallow channel, we continued to Rocky Valley, which is forms the top of the landslide and stopped briefly to consider the differences between rotational and translational landslides. 

 

A view west along Rocky Valley

From this point onwards, we were in unknown territory and my priority was to ensure that the remainder of our walk went as smoothly as possible. With Stephanie taking the lead, we carried on along the path in Rocky Valley and, with only loose boulders being accessible - some of which are known to contain plant fossils - the other group members were left to their own devices until we reached White Wells. 

 

A view east along Rocky Valley

I had not given any thought to this when planning this part of the walk, but there has been bathing at White Wells since 1703 and it was instrumental in establishing Ilkley as a spa town, with a number of large hydros being built in the second half of the C19. 

 

White Wells

 

The bath that was outside to the rear of the premises were replaced in 1791 by two baths, one of which is on display today and is still used, particularly to celebrate New Year’s Day. It is not classed as a mineral spa, with the coldness of the water being supposed to promote circulation, and Charles Darwin is believed to have "taken the waters” when he visited in 1859. 

 

The plunge pool at White Wells

 

Having had the opportunity to take a short break to look at the plunge pool and purchase something from the shop or use the toilets, we then headed down the path to the largely man made Ilkley Tarn, before making our way down to Cowpasture Road and up Hangingstone Road to the car park and then finishing the day at the Cow and Calf Hotel.

 

Hangingstone Road

A Recce at Ilkley Moor - Part 2

 

An information panel at the Lanshaw Lad boundary stone

After taking our lunch in Hangingstone Quarry, having discovered the location of the slickensides during our recce of Ilkley Moor for the Sheffield U3A Geology Group field trip, in August 2024, we went in search of Site 7 highlighted in Ilkley Moor - Its Geology and Heritage (IMIGH) by Gareth Martin and David Leather. 

 

A large glacial striation above Hangingstone Quarry

 

When studying A Level geography back in 1978, I was taught about glacial striations, caused by the scouring of bedrock by lumps of harder rock that were embedded in the base of the glacier that flowed over it but, to the best of my knowledge, I had never seen any of these in the Scottish Highlands or the Lake District, while studying geology at Nottingham University. 

 

Glacial striations above Hangingstone Quarry

 

Those on Ilkley Moor are described as “some of the finest examples of glacial striae” that can be seen in the UK with a west-east direction and their height of 150 m above the valley floor indicating the minimum thickness of the glacier. 

 

The Crocodile's Mouth

Finding one of the many paths that criss-cross Ilkley Moor, we stopped briefly to look at the geomorphological feature called the Crocodile’s Mouth and then carried on alongside Backstone Beck, which runs along a fault controlled valley. 

 

A view towards the waterfall on Backstone Beck

The beck flows through quite a deep valley with steep sides, which changes abruptly into a small channel upstream and is marked by a waterfall. This is interpreted as a knickpoint, which is eroding up slope and was possibly a response to the formation of a hanging valley during the glaciation of Lower Wharfedale in the Pleistocene Epoch. 

 

A view of the mass movement deposits beyond Backstone Beck

 

Looking south along Backstone Beck, the very undulating bracken covered landscape that is seen beyond the valley is due to the mass movement deposits, which are a common feature of the north facing slopes beneath the Addingham Edge Grit along Lower Wharfedale and was seen during the field trip to Otley Chevin. 

 

Mass movement deposits at Ilkley Moor

 

Continuing along the unmarked path to a viewpoint, where the very worn public footpath from the Cow and Calf Rocks fords Bakestone Beck, we briefly looked for the unusual coarse gritstone mentioned in the IMIGH geological trail; however, I didn’t see anything that stood out from the many examples of very coarse sandstone from the Millstone Grit Group, which I had seen on my travels in South Yorkshire, Derbyshire and West Yorkshire. 

 

A view down the path from Backstone Beck to the Cow and Calf Rocks

The next location on the geological trail was Rocky Valley, which marks the top of a rotational landslide, with Ilkley Crags forming its crown and the main scarp immediately beneath it. Having located the well used public footpath, we didn’t spend any time investigating its principal features, which can be seen from a distance, and set off to find the remaining 7 locations. 

 

Ilkley Crags and Rocky Valley

It very soon became obvious that the moorland here is again criss-crossed by a network of very poorly defined paths, which are marked on the 1:25,000 scale Ordnance Survey (OS) map but are not classed as public rights of way and signposted. 

 

The OS map covering the southern part of the geological trail

 

There are no obvious landmarks from which to get your bearings but, once we managed to find a path that crossed over Bakestone Beck, we kept close to the beck and carried on until we found the prehistoric Bakestone Beck enclosure and huts, which archaeological excavations suggest are late Neolithic (c.3000 BC) and late Bronze Age to early Iron Age respectively (800 to 500 BC). 

 

The Bakestone Beck enclosure and huts

 

Continuing along this path, we then encountered the Poetry Seat and Poetry Postbox, which forms part of the Stanza Stones Poetry Trail from Marsden to Ilkley, with poems by Simon Armitage cut into large stones by Pip Hall – the lettercarver whose work I had also seen on the Kilkenny limestone seats on The Moor in Sheffield.

 

The Poetry Seat and Poetry Postbox

Since leaving Rocky Valley we hadn’t seen any outcrops of bedrock, but a little further along the path I was interested to see a lump of very coarse gritstone sticking out of the path, which contained a bed of finger nail size quartz pebbles. Looking at the geological map, the underlying bedrock here is the Long Ridge Sandstone in the Millstone Grit Group. 

 

A detail of the pebbly gritstone in the path

So far on our recce, we had found most of the locations on the geological guide with relative ease, although the network of paths on Ilkley Moor is quite confusing and some of these would benefit from better descriptions of the precise locality and grid references. 

 

A Google Map view with Lanshaw Delves marked in red

 

Arriving at the Dales High Way, which is laid with flagstones, next on our list of places was Lanshaw Delves, is a west-east trending lateral moraine that is described as being approximately 600 m long by 40 m wide by about 3 m high. The Google Map satellite view and the OS map show that its western end is 115 m beyond the point where another public footpath splits off from it. 

 

The beginning of Lanshaw Delves on Google Street View

 

Keeping our eyes open for the junction of the two footpaths, we didn’t see any sign of this or any feature in the landscape that suggested that we had arrived at the beginning of a moraine and continuing along the Dales High Way and reaching the Lanshaw Lad boundary stone, we realised that we had completely missed this feature. 

 

The Lanshaw Lad boundary stone

Consulting our various maps, we thought that it would be easy enough to locate the path that would take us to the east end of Lanshaw Delves and carried on along a well established path past The Twelve Apostles stone circle. 

 

The Twelve Apostles stone circle

 

Failing to locate the public footpaths marked on the OS map, we had to stop three times to ask local walkers for help in finding a path that would enable us to get back to the Cow and Calf car park by the quickest route, without having to retrace our steps. All of the people we talked to told us that the paths on Ilkley Moor are notoriously difficult to navigate and, despite trying to follow their directions to the best of our ability, John and Trish had to use their GPS apps to get us to the Dales Way/Ebor Way. 

 

The OS map showing paths on our return from The Twelve Apostles

 

When we set off from Rocky Valley, the time was 13:34 pm and the route marked on the IMIGH geological trail covered a distance of 3.25 km. We had been confident that we would be back at the Cow and Calf car park well before 15:30 pm, which is the usual finishing time for field trips; however, although we didn't get completely lost, by the time we arrived at Hangingstone Road it was 16:23 pm. 

 

A distant view of the Cow and Calf Hotel

 

Finally arriving at the car park, we then finished what had turned out to be a very long and tiring day by enjoying a drink in the late afternoon sunshine at the Cow and Calf Hotel. Having collectively decided that we would have to revise our plans for the actual field trip two weeks later, we then set off on the long drive back to Treeton.

The Cow and Calf Hotel

A Recce at Ilkley Moor - Part 1

 

The Calf at Ilkley Moor

Following on from my day out to Leeds, where I learned a lot about the history of the canal and railway and its various industries, my attention next turned to a recce for the August 2024 field trip with the Sheffield U3A Geology Group to Ilkley Moor. 

 

The Ilkley Moor geological trail

 

On a few occasions the group had made good use of geological trails and walks produced by the West Yorkshire Geology Trust and the Leeds Geological Association, with Bill Fraser leading trips to Roundhay Park and east Leeds and Gareth Martin showing us around Wharncliffe Crags. 

 

The route of the geological trail

 

The group leader, who I had undertaken several recces with, had been suffering from poor health and this time I was very glad that John and Trish had volunteered to provide transport and help with the preparation of this field trip. They are seasoned walkers who are equipped with satellite navigation devices and Ordnance Survey maps and, although we had carefully researched the walk using a variety of other online maps, we discovered that the southern part of the route is far from easy to follow. 

 

Treeton and Ilkley Moor

 

Setting off from Treeton and driving up the M1, our route via the M62, the A677 ring road around Bradford and with views of the countryside beyond Bingley was much more enjoyable than the sat nav route that was taken by the group leader on both the recce and field trip to Otley Chevin, which involved a convoluted tour of the eastern part of Leeds. 

 

The Cow and Calf Rocks

Arriving at the car park off Hangingstone Road, we could clearly see the crags of Addingham Edge Grit that form the Cow and Calf Rocks and which the group had seen at Otley Chevin and I had encountered as a building stone in the former Leeds School Board a few days before.

 

The geology of Ilkley Moor

Following the path, which is laid with flagstones that contain ripple marks and were salvaged from one of the old textile mills in the area, our first stop was at a large boulder next to the path, which has an eroded tube shaped void in it. 

 

Salvaged flags on the path to the Cow and Calf Quarry

This is a fossil imprint of the Upper Carboniferous Knorria, the inner pithy layers of the Lepidodendron club moss from which the outer layers of bark have been shed. Looking closely at the very coarse grained sandstone, this would have been formed in a large river channel and the fossil would have been derived from the swampy forest along its river banks. 

 

The Knorria fossil

 

Next on the route was the large slumped block known as the Calf, which is 11 m high and was detached from the main outcrop by the ice sheet that covered Lower Wharfedale 10-12,000 years ago, with it subsequently sliding downslope and rotating at an angle of 140 degrees. 

 

Following the path to the Calf

 

Making our way into the large Cow and Calf Quarry, in several places the deeply iron stained quarry faces are covered in graffiti, which has been carved into the very coarse grained and frequently pebbly Addingham Edge Grit. 

 

Graffiti marking a climbing route in Cow and Calf Quarry

On the day of the field trip a couple of years later, a local resident who joined the group for this event explained that some of these, including the “OLD CRACK AND RACKETY JACK”, are the names of climbing routes that were roughly carved into the gritstone by some of the rock climbers who frequented this very popular locality. 

 

Cow and Calf Quarry

 

Leaving the quarry and making our way along another path to the heather and bracken covered moorland above it, we obtained a good view down into the quarry and of the glaciated valley of Lower Wharfedale further in the distance. 

 

A view to Ilkley Crags

 

To the south, the ground rises to form Ilkley Crags but we headed north to the escarpment of the Cow and Calf Rocks overlooking Ilkley, where the gritstone is covered in graffiti that largely dates to the C19. Most of these have been carved by visitors who frequented Ilkley when it was a fashionable spa town, with many of them showing a high degree of letter cutting skills. 

 

Victorian graffiti and views of Wharfedale from the Cow and Calf Rocks

Taking in the views of Wharfedale, we then continued to the Hangingstone Quarry and went to look for the cup and ring marks, which are one of over 400  that are found in the area – mainly scattered around Rombalds Moor to the west – and date back to the Neolithic or Bronze Age. 

 

Cup and ring marks

Very near to these marks, which have been cut into a surface that has been scoured by ice, is a large rock that shows very distorted bedding that is known as soft sediment deformation. These are created by the escape of water, caused by rapid squeezing of the sediment and the expulsion of water during slumping or tectonic activity. 

 

A rock with soft sediment deformation

 

Dropping back down into the floor of the quarry, we then went in search for the next location on the geological trail, a set of slickensides, which we eventually found in the south-west corner of the quarry at high level. 

 

A rock face with slickensides

 

The brown polished face marks the place where the rocks on each side of a north-south aligned fault plane have ground against one another to leave a series of closely spaced lineations. The rocks are dated as c.310 million years old and the movement along the fault must have taken place at a later time, but there is no way of assigning a date to this.

A detail of the slickensides