Hayley Pearcy. 11Gio
GEOGRAPHY COURSEWORK: THE RIVER LANDSCAPE.
Question 3.
I have identified a meander as the first feature of my sketch. There are many meanders shown along the part of the river shown in this photo. I am describing the one that comes first as the river enters the page at the forefront of the picture. Here the river flows what looks to be straight and then it turns back on itself to form the beginning of another meander.
On one side of the meander there is a break of slope, a river cliff. It is quite large and the soil exposed is fairly sandy (milstone grit) and contains fragments of white rock that could be limestone. This soil has clearly been slipping down, as at the base of the cliff there are fragments of this rock littering the side of the river some of these rocks may have been deposited from further upstream. The sandy soil will probably have been carried away by the flow of the river. On the opposite side of the meander there is an area of flat land. This is the slip-off slope of the meander. Unlike the river cliff side, the slip off slope side is covered in grassy vegetation. The thickness of this vegetation increases, as it gets closer to the river. There is a very visible band showing these two thicknesses.
The second feature that I have highlighted is the scar. This is an area of the valley side that has collapsed to expose the soil underneath. It is quite large as it extends from the top of where the hill starts to slope sharply down into a valley to the floor of the valley itself. The amount of exposed soil increases further down the scar as is gets wider. There are clearly rocks visible that have been exposed with the soil. These are of the same kinds that were exposed on the river cliff. The soil looks to be the same sandy kind as well. The scar is not too deep and it looks to be only the top layer of soil that has slipped off. The base of the scar leads directly onto the outside bend of a meander and there seem to be an increasing amount of rocks as you go down the scar and a mass of rocks at the base of it and at the bend of the meander.
Question 5.
Over time different processes have shape the landscape in this picture to make it look the way it does now. This photograph shows a small, u-shaped valley with a small river at the base of it. There are many other landforms shown along the small section of river in the photo. These landforms have evolved with time from what was a section of plain, flat land many years ago. The diagram below shows what the land looked like before different processes shaped it.
So what happened to result in this drastic change?
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Question 5.
Over time different processes have shape the landscape in this picture to make it look the way it does now. This photograph shows a small, u-shaped valley with a small river at the base of it. There are many other landforms shown along the small section of river in the photo. These landforms have evolved with time from what was a section of plain, flat land many years ago. The diagram below shows what the land looked like before different processes shaped it.
So what happened to result in this drastic change?
During the ice age, huge glaciers moved slowly across the land, shaping it and scouring it. It is possible that a glacier scoured away part of this valley to form a channel that then became the course of the river in the picture. The glacier will have scoured away the soft boulder clay leaving exposed the limestone and millstone grit. The glacier would have followed the path of water (only it was in the form of ice or snow) from the uplands so it would have been natural for the water to follow the same path after the glaciation period. The flowing water will follow this same path for some time and all this time it will be changing the landscape around it. It will be constantly eroding the river horizontally and vertically. This is due to the various erosional processes that take place within the river, hydraulic action, where the water in the river erodes the bed and banks of the river, abrasion/corrasion, where pebbles, rocks and other materials collide with the banks and bed of the river and erode it, corrosion, where the water dissolves substances, in this case the limestone rock and attrition, where the materials within the river collide with each other and break each other apart.
The diagram above shows the different erosional processes acting on the river course. You can see that this has been happening in the picture, as there is the large valley, which is a result of this action.
As the river flows downstream is begins to meander. These meanders form their own landforms along the river.
Above is a cross-section of a meander. It shows that on the outside of the bend there is a river cliff and on the inside there is a slip off slope. Varying energies of currents forms these. As the water is flowing straight and it can't tell when a meander may come up, it just carries on flowing straight. This results in the water hitting the outside of the bank with a force, it then bounces back off the bank and carries on at a different angle as show in the picture below.
This means that on the outside of the bend, the force is strong. It has enough energy to transport larger materials and also enough energy to erode the bank through hydraulic action and corrasion/abrasion. On the inside of the bend however, the energy of the river is low, therefore not many materials can be transported so they are deposited causing a bank to build up (slip off slope). Over time, the force of the water on the outside of the bend can wear away the rock so much that it undercuts the bank. This can eventually lead to the overhanging section of bank to collapse and then be transported away by the river.
Meanders appear in the photo I was given and evidence of the processes that I have just been describing are visible. In the bottom left corner, there is a section of the valley on the outside of a meander that has been eroded away. The soil and rock underneath is exposed and there is a pile of rubble left underneath the cliff that is part of the collapsed bank but the material is too heavy to be transported away at this stage. There is also a slip off slope that can be seen. No erosion is visible and the vegetation on the slip off slope suggests that it has been around for a while.
It is clear that transportation and deposition have gone on along the river. Transportation is where the river carries materials in four different ways,
* Traction. Where the force of the water rolls rocks and boulders along the riverbed.
* Saltation. This is where smaller stones and pebbles are carried along the riverbed.
* Suspension. This is where smaller particles such as silt are suspended in the river.
* Solution. This is where minerals are dissolved in the water so are carried along with it.
The picture below shows these four different methods of transportation in action.
In the picture, transportation can be noticed when you look at the outside of the meander. There are the limestone rocks visible that have fallen from the cliff however the finer millstone grit cannot be seen anywhere as this has been transported downstream.
Deposition can be seen in a few places. On the inside bends of the meander where the slip off slope has been formed, this is formed by deposition and all along the course where there are large white rocks to be seen in the river, these are there as a result of deposition. Deposition occurs when a river loses its energy so it cannot therefore carry the larger material. This tells us that the energy of this river is always changing. At this point is must have slowed down for deposition to occur. There is evidence that the river flows in one direction as some erosion such as at the confluence, is only occurring going away from the photographer suggesting that the water is going this way. The sketch from the photograph below makes this clearer.
This is an upland area and is made up of limestone and millstone grit. The limestone is in mostly large pieces embedded in the millstone grit. This combination means that is fairly easy to erode, the grit is fine and can be eroded and transported easily and the limestone is simply left to built up until a force is great enough to transport it away. Also there is little vegetation in the area of the photo so the ground is open to weathering. Once the small layer of grass and moss has been removed the limestone and millstone grit is left exposed. Because this combination of limestone and millstone grit is not very stable, it can result in landforms on the valley side that occur when rain runs down the slope. Gradual soil creep causes terracettes which are the small step like features in the centre of the picture and also scars where the top layer literally slides of the one underneath.
The valley in the picture is of an irregular shape, some of the valley has been eroded further back than the rest and the slopes occur at different degree angles. This shows that erosion has taken place at different rates on different parts of the slope. This could be due to a change in rock type or force of the river as it gradually erodes down.
There is also evidence of human influences on the land as there is a dry-stone wall built from the top left of the photo to the river. There is also a small bridge in the distance of the river for crossing purposes. The dry-stone wall suggests that at some point in time people will have taken some of the limestone rock from the nearby land to build it thus changing the landscape. The small bridge seems to have been built of the same material. The wall looks to be collapsing now an already some of the rubble seems to be reaching the river to be transported. There is a clear depression in the ground where the wall lies. I believe this to be where rainwater has run down alongside the wall as run-off and throughflow and gradually eroded down as it carried away material off the land down into the river.
All of these processes have worked together to shape the land to what it is now in this picture.
Bibliography of sources.
* Sheet handed out in class.
* 'People, places and themes' by Alan Bilham-Boult, Heather Blades, John Hancock and Mike Ridout.
* Geography GCSE revision guide by COLLINS.
* GCSE success-Geography by Letts.
