Bakewell's stone built bridge over the River Wye, which is Grade 1 listed, dates from about 1300. There are five Gothic arches on its lower side with the upstream side, which was rebuilt in the same style during the 19th century, having been repaired several times. The bridge is built from sandstone
Sandstone is one of the most common types of sedimentary rock and is found throughout the world. It is often mined for use as a construction material or as a raw material used in manufacturing, and often serves as an aquifer for groundwater or as a reservoir for oil and natural gas.
It is a sedimentary rock composed of sand-size grains of mineral, rock, or organic material. It also contains a cementing material that binds the sand grains together and may contain particles that occupy the spaces between the sand grains. The grains of sand in a sandstone are usually particles of mineral, rock, or organic material that have been reduced to "sand" size by weathering.
Weathering is the process where rock is dissolved/corroded or broken down into smaller and smaller pieces. Rocks and sediments are picked up and moved to another place by ice, liquid water, wind or gravity. Once the rock has been weakened and broken up by weathering it is ready for erosion. The base of the bridge here will have been eroded by the river's current through processes such as hydraulic action, attrition and solution, with stronger currents generated by storms, wind, or possibly motor craft on this river wearing down the rock even more. This includes losses of sediment and rocks, or just the temporary redistribution of sediments (deposition). The rock may also be subject to abrasion, where stones carried by the permanently flowing river grind across it. In addition, the river has flooded previously and often in stormy conditions will also carry, for example, parts of broken tree branches
Physical weathering – a physical force breaks down rocks into smaller fragments. Freeze-thaw action is the most well-known type where expanding ice forces cracks to open splitting rocks apart. The growth of salt crystals in cracks in coastal rocks works in a similar way.
Chemical weathering – rocks are affected by acids and corroded by solution weathering; rainfall is weak carbonic acid although the acidity of rainfall can be increased by pollution. Absorbing these substances turns the rainwater into a weak carbonic acid which then corrodes the rocks it comes into contact with. Rocks made from carbonate minerals, chalk and marble for example, are particularly susceptible to chemical weathering.
Biological weathering – plants and tree roots can split rocks apart, and algae and lichens growing on rocks release acids, which will contribute to chemical weathering also.
To complete this EarthCache, you need to answer the following questions:
1) Describe the texture of the rocks on the inside bridge wall (road-side) compared to outside (grass-side), and why this is.
2) Explain the long term impact that the river is having on the structure of the base of the bridge, referring to the 5 'tunnels' under the bridge.
3) Using the information in description, suggest whether the bridge has been affected by physical/chemical/biological weathering, and what evidence can you see for this
Please send your answers via message at the same time as you log the cache. I will reply as soon as possible.