The Devils Bridge has much history, an ancient medieval structure, though sometimes sat that the crossing may be older, with a wooden bridge just upstream. It is also a place of lore, with the story of an old woman wanting to cross here, and her dealings with the Devil.
This EarthCache takes you right underneath the bridge, though there is no need to abseil down. At the Kirby Lonsdale side of the bridge, a gap in the wall leads down to steps, then there are some rudimentary paths that lead down underneath the bridge.
⚠️ Be careful it is uneven under foot.⚠️
⚠️ When the limestone is wet, it is extremely slippy.⚠️
⚠️ If the river is running high, or in spate, DO NOT ATTEMPT THE EARTHCACHE. ⚠️
The above photographs show where you need to look.
🤔 What are we here to look at?
Well, we are here to look at the Urswick Formation Limestone, but more specifically how the environmental conditions changed during the geological period, which is now represented in the geology that we can see.
🤔 Urswick Formation Limestone.
The environment that this limestone was deposited in, is very different to where you stand today. It was deposited initially as sediment in a shallow tropical sea, 340 millions of years ago, when this location was located in the tropics, south of the Equator. The sediment was formed of lime mud and ancient sea creatures. There is a lot of limestone about here, so what is special about this location?
We tend to think of the tropical marine environment, of just being that tropical sea, with fish, corals and shellfish in water, and that it was like this all the time. Though during the period that the Urswick Formation Limestone was deposited, it was a varying environment, and this is represented in the geology. Urswick Formation Limestone shows evidence of a shallow water depositional environment with what is known as emergence occuring at times.
🤔 What is emergence?
The sea level rose and fell at times, and this affected what sediment was deposited. At times due to fluctuating sea levels, this lead to periods where the seafloor was exposed to air and weathering, this is known as emergence. These exposed surfaces, called palaeokarst, are sometimes preserved as fossilized soil horizons (palaeosols) within the limestone.
🤔 Palaeosols.
Thin layers of fossil soil, called palaeosols, formed on top of the limestone during these emergence periods, and here we have evidence of a palaeosol in the geology we can see. They can be found in marginal marine and even marine strata if sea levels drop to expose the seabed.
📝 This being an EarthCache, in order to log it, I ask that you complete the above tasks. Please send the answers 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 this area of palaeosols, in terms of colours and textures. How does it compare to the other rocks nearby?
2. Please explain what an emergence is.
3. Please look at the other rock layers nearby, what would they indicate happened to the environmental conditions?
4. Please have your photograph taken looking up at the bridge, you can also take a picture of your device.