Limestone was formed about 330 million years ago in the Carboniferous period. This is a permeable or pervious rock, which means that it allows water to pass through it. This rock is made of Calcium Carbonate and therefore erodes with the droplets of acid rain which have carbon dioxide dissolved in them. This is called chemical weathering. The water is able to pass through the carboniferous limestone as this rock has bedding planes and joints. The joints are the stress cracks in the rocks that occur when the plates come across resistance which makes the rock buckle. The bedding planes are the layers of weaker rock, which is present between two layers of stronger rock.
The natural landforms in limestone areas can be divided into surface and underground landforms. These surface landforms include the swallow and resurgence holes, which are part of the River Yeo drainage system. Cheddar gorge is a very impressive part of Cheddar. The magnificent sheer cliffs and winding valley floor gives u a picture of what it once looked like as the river passed through and slowly carved out the Gorge. The gorge is about 2.8 kilometres long, of high and even intimidating cliffs, which reach to a high of around 200 metres, and vegetation and different kinds of animals.
There are a number of possible theories on how Cheddar Gorge was formed. The ‘cut back waterfall’ theory is just one of them. Many people believe that a waterfall once flowed over the gorge. This waterfall kept cutting back until the Cheddar Gorge was formed. This is a good theory but still not as convincing as a good theory should be.
Another theory is the one on the ‘collapsed cavern.’ The underground river that slowly eroded away the Carboniferous limestone would have caused this. But many experts don’t agree with this theory because they all agree with that this would have taken much to long to happen. This would take time because chemical weathering is so slow in the surrounding climate in Cheddar, even millions of years ago.
The theory that many geographers favour is the one that occurred at the end of the last ice age. At this time the temperatures would have been extremely low. This would have caused the water that filled up the cracks in the rocks to freeze, which meant that the limestone was no longer pervious, but impermeable. This caused all the water to run over the rock instead of passing through the joints and bedding planes. This made the river cut a steep gorge.
This is the theory that I believe is the most likely to be true because it sounds like the most realistic one. It is also the one that the professionals and the experts believe is true, therefore they must have some evidence to back it up. The other theories don’t sound as convincing because it takes millions of years for the gorge to be made if those other theories were true.
A number of underground features can be found in Cheddar, ranging from the caves themselves to the stalagmites and stalactites. On our trip to Cheddar we went to look at Gough’s caves and the museum, shown on the grid reference 468539. our tour of Gough’s caves was a very informative one and helped me in learning about the different features. In the caves we saw stalagmites and stalactites and the different type of each that u can get. The columns were also visible. The tour guide explained to us that a column is formed when both stalagmites and stalactites join together it eventually ‘emerges’ into one column. Flowstone was also another interesting feature in the caves. This was because you could see the ‘diamond like’ sparkles. Different colours may also be visible in the flowstone. I was amazed at all the chambers that where there and at how big they were, and the different features in each of the chambers. The second cave, Lox’s cave that I visited was very different to Gough’s cave on a way that it had been ‘transformed’ into more of a tourist attraction. Aladdin’s cave was also a good cave to look at different features, but again, it had a ‘touristy’ feeling to it as it had illuminated areas. Reflections of the features in the mirror pool were also good to look at. This cave also dhows the different colours in the flowstone, caused by iron oxide, which made the stone red. Copper minerals made the stone go green and the lead minerals made the stone go grey. All of these features take tens of thousands of years to develop to the stage that they are now and that is why these caves are an important place, especially because Cheddar is the only Limestone built area in the South west of England.
At the end of the trip to Cheddar I realized that I had learned many things that I never new bout. The nature of the limestone is amazing as can be seen, where stalagmites and stalactites, and flowstone and columns and chambers can be formed out of just one type of rock.
