This EarthCache takes you to the edge of the limestone scar, known as Runscar, or Great Scar. There is NO need to get up to the limestone, your feet need to be on the ground. We are here to look at a feature known as a Karren.ย ย
So, first, why the EarthCache name? Well, recently on a geology tour of the locality, I met Trebor, another geocacher, with a specific interest in EarthCaches. It was at the EarthCache location, that an academic discussion was had about this specific karren. The discussion started with sedimentary structures, and then specific karren features, and soon his walking stick was pointing to features. One specific feature was highlighted as being of interest, with the question of what, how and this is why. The discussion continued, arms rested on walking poles like a Dales farmer, and the conclusion was that look further into subject, and at the next meeting, either at the discussion forum, or the next discussion event, we would then present our theories.ย Ultimately, EarthCaching, leading to further knowledge and expansion of understanding of the limestone environment.ย ย
๐คSo what was of interest?๐ค
The edge of the limestone scar forms an abrupt wall, in which there are a number of features, but it was the holes that drew the attention, and specifically the pointing of the walking stick. You may ask, why holes, as there are loads ofย fearures, but a certain type of hole. Following lots of reading, it became apparent that it was Cockles, that were of interest.ย
Let's discuss the geology first.
Runscar is basically limestone.ย Limestone is aย sedimentary rock, which was formed during the Carboniferous period, when the area was actually a tropical sea. Over time, lime mud and the remains of ancient sea creatures build up on the sea floor as sediment. Further sediment built up, and eventually over time, limestone was formed.ย Jump forward to the ice age, and then the limestone was uncovered by glacial action. Imagine Ribblehead without the viaduct, all the cars, roads, and the hordes of walkers. At the end of the ice age, there was a barren landscape of rocks, clay, mounds and barren limestone pavements.ย These had been exposed and scrapped clear by the glaciers. Limestone is formed of calcium carbonate, and over time, the limestone pavement was subjected to erosion, and solutional forces. Water erodes limestone, as it bonds with carbon dioxide to form a mild acid called carbonic acid, and this basically over time dissolves the limestone.ย ย
What are cockles?
Cockles are a type of Karren. Karren are features on limestone caused by erosion. Cockles are found on vertical or near vertical expanses of limestone, and are commonly hemispherical in shape. The question is, how fo they form? Well, some sources say similar to rainpits. Rainpits, are another type of karren.ย Water picks up carbon dioxide in the atmosphere, snd a weak acidic solution is formed. As rain hits the limestone, it causes carbonation. This is when carbon dioxide reacts with the calcium carbonate in limestone and dissolves it. This happens slowly over time, and eventually shallow puts called rainpits develop. Eventually rainpits contribute to the development of other karren features. You may ask therefore why aren't there cockles all over the vertical face of the limestone, but part of undertaking an EarthCache is looking and learning.ย ย
This being an EarthCache, in order to log it, I ask that you answer the below questions. Please send them to me, and do not include them in your log. You can send them to me by using the message facility or email, both of which can be found by looking at my profile.
1. Please describe the cockles in terms of their distribution across the limestone, or are they in any specific locations?
2. Please look at the limestone face in front of you, would you describe it as completely vertical? How would this contribute to cockles formation?
3. As cockles continue to form, what do you think will eventually happen?