This is one of a series of EarthCaches placed at sites within the Westmorland Dales area which the Cumbria GeoConservation group considers as being good examples of various aspects of the local geology. Our geological research has been made possible by the Westmorland Dales Landscape Partnership Scheme, jointly led by the Friends of the Lake District and the Yorkshire Dales National Park Authority and has been grant funded by the National Lottery Heritage Fund.
This narrow railway cutting was once the site of the South Durham and Lancashire Union Railway, opened in 1861, running between Barnard Castle in County Durham to Tebay in Cumbria and built to carry coke from the Durham coalfield to its ultimate destination in the iron furnaces of Barrow. It was closed in the 1960s and the track was lifted soon after. The cutting now forms part of the Waitby Greenriggs Nature Reserve, owned and managed by Cumbria Wildlife Trust. There are displays about the wildlife of the area, and a bird feeding station, at the car park.
As you walk along eastwards, you will see beds of pale limestone on both sides of the path, but once you reach GZ, the rocks are entirely different. If you look further along the cutting, you will see the dipping limestone beds again. So the rock in the middle appears to be filling in a hollow in the limestone. Based on similar features elsewhere, what you are looking at is probably a cross section of an infilled channel in the limestone, crossing the cutting.
We are able to deduce a really interesting series of events from these observations. About 350 million years ago, the area that is now Britain lay in tropical regions and was covered by a clear, warm sea. The sea was teeming with life, and their shelly remains fell to the bottom when they died, as we can see from the fossils that we now find in the limestone. By about 300 million years ago, the sea level had fallen and this area was now land, within a large continent called Pangaea. We lay somewhat north of the equator and were experiencing desert conditions. Around the desert were mountains where storms often occurred, so conditions would be a bit like those currently in Arizona - think Death Valley - in the USA. Here, when there is a rainstorm, the water rushes down from the mountains, carving gullies in the desert sides, and carrying boulders, pebbles and sand. Then, when it reaches the desert floor, the water drains away, and the mix of boulders, pebbles and sand is left in the gullies and on the floor of the desert. What you see here is a cross section of one of those gullies, carved by rushing water on one wet afternoon 300 million years ago and now mostly filled with some of the material that was being carried when the water drained away. Amazing stuff!
With thanks to Cumbria Wildlife Trust for permission to set this EarthCache.
Questions:
To claim this EarthCache, please send your answers in a message, either by e-mail or through the Message Centre. Do not put them in your log. You do not have to wait for a reply before logging; if there is a problem with your answers we will let you know. Pictures of your visit are very welcome in your log, but please avoid giving away any of the answers.
1. As you walk along the cutting towards the channel at GZ, in what compass direction are the limestone beds dipping and at roughly what angle?
2. Describe the rock pieces in the channel. How do they compare with the limestone beds that you have seen on either side of the channel? What is the range of sizes? What is in between the rock pieces?
3. This question is about the shapes of the rock pieces in the channel. If the rock pieces have not travelled far, they will be angular in shape, with sharp corners, as they have been broken away from the original rock. If they have been carried from some distance, then you would expect the sharp corners to have been rounded, as the pieces were rolled about in the water. Describe the typical shape of the pieces and thus decide whether they have been carried a long distance or not.
4. Look at the material at the far end (the eastern end) of the channel. How does it differ from the material in the main part of the channel and where might this material have come from?