Now making sure the tide isn't in or coming in make your way north along the side of the beach and over the waterbreak (rusty ladder) and carefully over the rocks to GZ.
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The cliffs and foreshore also exhibit unusual folds that deform the sequence of turbidites; these are the layers you can see built up over million years when the area was underwater and layers of sediment built this rock while under pressure. These folds formet prior to the Caledonian phase of mountain building, approximately 400 millions years ago, and as such are an important locality for future research. The section of the coast is frequently visited by national and international specialists and is considered to be of exceptional conservation value.
The best understood geometry occurs where a fault tip lies in a ramp. Strata (rock) cut by the base of the ramp are shortened by thrusting (movement of the layers). Layered rocks above the tip of the fault are shortened by this folding. In-between layers of rock are shortened by a combination of the folding and faulting. Fault tips must occur through layers of rocks because the forces on the rock twist and turn the layer causing faults to develop. Hence this type of fold is called a fault propagation fold. It is possible for the fault tip to occur beyond the area of folding, leaving the fold truncated in the 'hangingwall' feature that can be seen at the foot of Consti, (where the layer has been pushed out and you see a bulge instead of a series of layers. - see waypoints.
The hole has formed through the sedimentary rock by a process of erosion by the sea. The reason this has formed a hole is that the fault line (look for the clear crack in the cliff, its very clean with no gap) is a weakness in the rock, and with the process of water entering and exiting over thousands of years it washed away the sediment slowly creating this little hole in the cliff.
If you walk onto the cache coordinates you will see, as shown below, a cove. In this cove a hole/tunnel has formed through it, due to erosion caused by the sea along this fault. This fault is all that remains of the anticline and syncline that you will of observed at the base of Consitution hill.
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To claim this cache as a find you must please do the following :-
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| 1. |
(OPTIONAL- but very desirable) Please go to this hole and take an image of either yourself or your GPSr to see how this hole progresses in size. Any other pictures are appreciated but of course not required. Please check the tidal times on the 'related web site' above, they are accurate and show for a couple of years ahead. |
I have seen a picture taken about 10 years ago, and the hole has indeed got both wider and more dulled around the entrance and edit, this will help to give a visual record, but is optional. |
| 2. |
Estimate the size of the hole caused by the coastal erosion at its southern end (at the GPSr Ground zero) - this forms the mouth of the fault hole. |
This will give a record to see if the motion of the water through the hole will increase the weathering, and dull the sharp rocks with time |
| 3. |
Estimate the width of the hole as it most narrow point, you might have to stand back to get a good view through (its near a pointy bit as I see it). |
This will help to keep a record of how the hole is widening under the effect of coastal erosion. |
| 4. |
Estimate the height of the hole from the ground when you are standing in front of it. |
This will act as a record to see if the base of the cove is eroding away. |
Please message me your answers, don't put them in you log as it will give the answers to everyone. But remember the answers are approximate, I'm not expecting you to turn up with a tape measure to take readings (but I guess it could be easier and more accurate).
PLEASE PLEASE PLEASE! be careful here it is slippy on the rocks, there are small ponds, loose rocks and the potential for loose rocks above, so i'd be weary near to the edges of the cove. I would advise heavily against Geokiddies here, and I would suggest telling someone you are going or go with a geo buddie. What ever the map looks like there is only one sensible access to this cache and that is via the iron stairs, access from the top of consti' isn't viable and would be VERY dangerous. I hope I haven't put you off to much!
Link to a great tide table set
This Earthcache is listed with the permission as a SSSI (Site of Specific Scientific Interest) by CCW (the Countryside Council of Wales). With specific thanks to Dr Mathews.
Also thanks to the SSSI report for a guide to the science described in this listing, and to leading me to this interesting feature in the first place.