Welcome to Pot Ridings Wood EarthCache!
This EarthCache resides on the Don Gorge, which is an area that has a long industrial history which primarily consists of quarrying limestone which is highly prominent in the area. Limestone is formed in two ways; one is by ocean-dwelling organisms such as oysters, clams and mussels use calcium carbonate, found in seawater, to create their shells and bones. As these organisms die, their shells and bones are broken down by waves and settle on the ocean floor where they are compacted over millions of years, creating limestone from the sediments and the pressure of the ocean. This is a reason to why Limestone often contains fossils of marine animals. The other way limestone is created is when water containing particles of calcium carbonate evaporate, leaving behind the sediment deposit. The water pressure compacts the sediment, creating limestone.
The limestone within the Don Gorge is called Magnesian Limestone (also known as Dolomite) and is the most likely type of limestone that you would find locally. It can be dated back to the Permian period which was 298.9 million years ago. Dolomite is generally formed in anaerobic conditions which means that it was formed in low-oxygen conditions.
The Don Gorge was formed due to receding ice flows of the last ice age. Major ice sheets have advanced and retreated across Britain at least 3 times in the last 500,000 years. The last ice age happened around 80,000 years ago, but had mild temperature breaks known as interstadials. We are currently living in an interstadial, known as the Flandrian warm period. Bones found within the area indicate that woolly mammoths and woolly rhinoceros' lived in the area around the end of the last ice age.
Water and wind can cause weathering, which is where the Earth's weather has an affect on rocks. Weathering is typically where water gets into a small crack in a rock and freezes, expanding the rock gradually, then it melts again and water gets deeper into the rock until it eventually splits into two or more smaller rocks. Limestone has calcium carbonate within it and when rain water comes into contact with it a chemical reaction can be caused and this results in a new substance forming but is then washed away which causes the limestone to start to wear away. This happens due to the fact rain water is always slightly acidic because of the carbon dioxide in the air. This is known as chemical weathering. Weathering and erosion played major roles within the forming of the Don Gorge as the glaciers that once dominated the land eroded away the rock to form this valley.
After the pieces of rock have weathered away, erosion occurs. Erosion is the movement of the broken parts of the rock away from the site where weathering occurred. Ice, wind, water and gravity all cause the rocks and sediments to erode.
Directions:
To get to this cache, you will need to walk from The Boat Inn up towards the Viaduct at the other end of the trail.
About halfway down, a gate should be on your righthand side, go through it and turn left. You will get to a large wall of rock going around in a crescent moon-esque shape. Look for the rock that has a pattern resembling a wave on it.
To get this cache, you are required to:
1) Describe the rock. How does it feel? What can you see in it?
2) Using the information above, please explain how you think that the Don Gorge was formed.
3) (Optional) Visit the location and take a photo of yourself with your GPS at the rock mentioned above and post it with your log.
We will accept answers through e-mail, info@dcrt.org.uk, or through the message centre.
Congratulations Muddy Woodies for FTF!