The rock formation at the GPS position is a type of grit stone. Gritstone is made up of fine grained mud and sand sediments formed of shale and siltstone, some with feldspar or quartz deposits, this is what gives it the rough texture. It is also known as Millstone Grit because millstones were made from it. As a delta advanced slowly outwards deposits of mud, sand and pebbles were laid down in successive layers on top of the other stone to make these gritstones.
Grit stone is a particular type of sandstone and is created in sedimentary layers. This can be shown in this outcrop by the distinct layers which have been exposed during weathering events. As the wind and rain beats down on these rocks, weaknesses are exploited and softer parts of the rock are washed away. When the rock is standing up like these, above other topography around it, this leaves a formation which, because it is weathered from all sides, looks like a series of flat round stones stacked up on each other. Hence the name of the cache.
As the rock is more and more washed away, weaknesses will make the rock unbalanced and pressures exerted on particular sections. This will result in stresses which make the rocks break.
Questions
- If you are lucky enough to have the sunshine oN the rock you will see it sparkles, what is causing this? (use your powerful torch) at about 450 if it’s not sunny
- The formation of the rocks has caused a cavity to be formed underneath, how far does it go in?
- Why are the rocks round at the edges?
- Underneath the large rock you can see a vertical break in one of the underneath stones, why has this occurred?
If you are willing and able please include a photo of your visit, underneath or on top would be good.