GUZZLE HOLE AND THE DAW PITS
This earthcache involves a walk through the upper Bishopston Valley (near to Bishopston village) to discover two interesting features. A collapsed cavern and an underground stream.
The valley actually runs from Kittle in the north to Pwll Du Bay in the south, and is owned and managed by the National Trust.
The valley is full of mystery and intrigue enhanced by its secluded nature. Co-located here is ancient woodland; caves; a prehistoric domestic/defensive settlement; industrial features; exploitation of natural resources; communication networks; post-medieval ruined buildings..
The coordinates given or for the Trailhead not the cache.
DO NOT DAMAGE ANY PLANTS OR REMOVE ANYTHING EXCEPT LITTER
The ancient woodland represents an area of enclosed wooded river valley, running approximately north – south. It is the predominant feature covering the steep valley sides. A stream wends its way along the valley floor, occasionally appearing and disappearing into holes and sinks in the limestone, and wet meadows fringe its banks.
The valley has a colourful past, once used by smugglers, miners and quarry workers, visible evidence of which can be seen as you walk through the valley to Pwll Du Bay. The buildings in the Bay were once public houses that served the quarry workers. The area of Bishopston Valley contains a few caves, with 'Guzzle Hole' being the easiest to reach. The sound of water rushing underground from the partly subterranean stream can make some rather unusual sounds, hence the name 'Guzzle'.
There are so many features to look out for on this walk, including the wildlife, historic features such as Long Ash Silver/Lead Mine and Iron Age Promontory Fort, caves and holes carved out in the limestone by water gushing through the valley down to the beautifully secluded Pwll Du Bay. If you’re quiet you may spot a kingfisher or otter by the stream.
GETTING HERE
By bus: Gower Explorer 118 and 119. Bus stop two minutes from the start of the walk. For further information see Traveline Cymru
By train: Swansea or Gowerton. Bishopston is then 6 miles/9.6km (15 minutes) by road
By car: From Swansea follow A4067 and then B4436 into Kittle
There is useful map attached in the image gallery, start at Kittle Green, walk past the National Trust sign and keeping Great Kittle farm on your right follow the footpath into the trees. The path drops down the slope for about 0.25 miles (0.4km) and can be slippery after rain. When you reach a fork in the path bare left and go down the steps until you reach the chestnut fence on your right. The enormous hole in the ground is called Daw Pit. This hole was formed where the underground river caused the cavern ceiling to collapse.
Continue down the steep slope to the bottom and turn right along the dry river bed. Cross the river to walk on the left hand side, taking care of the uneven surface for about 200yds (180m). The track crosses back across the river at this point. During wet periods the river will be running here, but it usually shallow and easily crossed.
THE ROCKS
Limestones form the bulk of the surface of Gower to the south of a line from Landimore to Bishopston and Oystermouth Castle. These grey rocks, which today form the spectacular cliffs of Pwll du Head, Great Tor, Paviland and Rhosili, had their origin far back in geological time, in fact over 300 million years ago.
The Carboniferous Limestone of Gower is between 3000 and 5000 feet in total thickness, the thickest succession occurring in the south-west of the peninsula. These grey rocks are today hard and compact, but they were laid down beneath the sea as sheet upon sheet of grey mud, some 330 million years ago. These mud sheets were originally soft but the weight of successive strata, together with the great buckling movements ,which later affected Gower, has helped to change these once slimy deposits into rocks which today clang when struck by a geological hammer.
At the time of their formation, the geography of Britain was very different from that of today. To begin with, the British area lay much nearer to the Equator of that time. It may in fact have beensituated almost on the Equator! Many parts of Britain, including South Wales,lay beneath a warm, mostly clear, sea. The temperature of the water was probably at least 70 °F and the sea teemed with life. Carboniferous limestone produces distinctive karst scenery. These areas are dry on the surface due to the permeability of the rock, but have mainly been shaped by the action of water.
Typical undersea conditions in Wales, when it was on the equator.
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Karst terrain is a type of topography that is formed by dissolution of bedrock in areas usually underlain by limestone. Such terrain has underground drainage systems that are reflected on the surface as sinkholes, springs, disappearing streams or even caves in this valley.
The term ‘karst’ refers to the terrain and the term sinkhole is one of the types of drainage features reflected by that type of terrain.
The water attacks the many joints and bedding planes in the rock, through the chemical weathering processes of carbonation and solution. It is attacked by streams and rivers and slight acidic groundwater percolating through. There are a number of distinctive features seen in karst scenery areas, both on and beneath the surface:-
- Limestone cliffs or scars are produced at the edge of the area of limestone. Often near vertical and highly jointed.
- Swallow holes and sink holes are where rivers flow down into the rock. Sink holes are relatively small, whilst swallow holes are larger. Both have been formed either by the constant chemical attack of the water on the joints in the limestone, or by the collapse of a cavern below.
- Caverns are underground caves that have been hollowed out by the action of underground streams and by carbonation and solution.
- Underground streams flow down through the limestone carving out caverns, until the y reach the impermeable layer of rock below the limestone layer. Once at this point the stream flows under the limestone until it re-emerges. This is called resurgence.
- Gorges are created where the roof of a large underground cavern falls in, to create a steep sided gorge with a river running in the bottom.
- Dolines are formed when the roof of a small underground cave falls in. The ground above the cave subsides into it causing an indentation on the surface.
- Dry valleys, such as Cheddar Gorge, were formed in periglacial times, when the ground froze, so the rivers ran over the surface of the limestone rather than flowing down through it. These rivers carved out steep sided valleys. Once the climate had warmed again the rivers disappeared underground leaving a dry valley behind. These also are common features of Chalk landscapes.
Click here for a useful link to an interactive map showing larger caves in Gower.
The source of the stream draining into Bishopston Vallley is a broadly Fairwood Common. This is a mixture of agricultural land and common land with shale and coal measure rocks underneath. The soil varies from peaty grey to red brown earth.
Sinkholes form in karst terrain principally from the collapse of surface sediments into underground voids and cavities in the limestone bedrock. Slightly acidic ground water slowly dissolves cavities and caves in the limestone over a period of many years. When the cavity enlarges to the point that its ceiling can no longer support the weight of overlying sediments, the earth collapses into the cavity. In the less catastrophic type of sinkhole, a bowl-shaped depression forms at the surface, usually over a considerable period of time, as surface sediments travel downward into small cavities in the bedrock.
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Sinkholes occur around the world . Some of them have a dramatic effect on people who live near them. Click here for some amazing pictures.
Barlands Quarry sinkhole has a number of openings in an area of general collapse and is partially filled with flood debris and waste from the quarry above. The Barlands Quarry Cave has a steep 10 metre drop leading to narrow passages and chambers about 450 metres in length
The valley sides steepen and evidence of collapse is seen at Higher Daw Pit. On the walls there is evidence of networks on undercut block. This suggests that there will be narrow passages but not necessarily a cavern. The steep sides of the pit and the absence of any signs of settling suggest rapid downward movement. It appears that the collapse is wholly with the limestone
Downstream from Higher Daw Pit, (question topic), the present course continues in a gravel floored channel
To the south is the lower Daw Pit which covers about 900 square meters and has collapsed below a slope of approximately 30 degrees The downslope (east) is about 6m high while the upslope is 24m high. The west slope is formed of alternating massive limestones and shales. On the southern side beneath an overhanging hanging block is a distinct ”spongework”, that is rock which has been partially dissolved by slight acidic water passing through.
Below this pit the normally dry stream is overgrown, with one or two little springs At this point in the valley the Bishopston Stream has descended underground long ago to the north.
The riverbed is extensively covered in moss and mulch, showing no signs of running water at all. However, you can definitely hear water flowing here. This cave called Guzzle Hole roars with the sound of the submerged river but all that is visible is shallow, pooled water.This is a partially abandoned resurgence where the stream can be seen flowing underground. Just inside the arched entrance in the west wall is a small tube accessible for 25 m by CAVERS, before a sump pool is reached.
Do not explore this cave unless you have permission and some caving experience and the correct equipment
Under dry conditions the stream can followed up stream until access to a small roofed chamber is possible. In flood conditions water resurges From Guzzle Hole and follows the surface course for some 14m to the permanent resurgence. Below this point surface flow continues to the sea at Pwlldu bay.
Acknowledgements
The Limestones of Gower by T. R. OWEN
Permission to place kindly granted by the National Trust
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1. Describe the first sinkhole you reach - Higher Daw Pit - and estimate its size, (HINT: use the description of the lower pit as a guide).
It is _______ metres deep on the down slope side with a face _______ metres high. Upslope it covers an area of about ______ square metres
2. Sinkholes would be most likely to occur in regions where the underlying bedrock is ___________
3. Describe what you see and hear of the mouth of Guzzle Cave and in the VERY long term what do you think might happen here?
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