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River Landscapes in the UK 1 (Transportation in a river (Solution…
River Landscapes in the UK 1
Interlocking spurs, waterfalls & gorges
Interlocking Spurs
Where a river winds between ridges
Waterfalls
Oftern occur where the river crosses a band of harder rock
Gorge
A deep valley caused by the wearing back of a waterfall
vertical and lateral erosion on a river
Vertical Erosion
When the land is eroded or worn away in a downward direction, e.g. a river that is high up will erode vertically becuase the gravity pulls the water downwards.
As a river flows downhill there is an increase in vertical erosion. The channel is shallow and narrow because there is not a lot of water in the channel.
Lateral Erosion
The wearing away of a landscape when a river erodes sideways.
As a river flows into the middle course, there is some vertical erosion but more lateral erosion. The channel is wider and deeper as a result.
River despositations
When the river loses energy, it drops any of the material it has been carrying. This is known as deposition.
Factors leading to deposition:
Shallow water
At the end of the river's journey, at the river's mouth
When the volume of the water decreases.
A river’s profiles
Long Profile
A long profile is a line representing the river from its source (where it starts) to its mouth (where it meets the sea). It shows how the river changes over its course.
Cross profile
A cross profile shows a cross-section of a river’s channel and valley at a certain point along the river’s course.
Transportation in a river
Solution
Minerals are dissolved in the water and carried along in solution.
Suspension
Fine light material is carried along in the water.
Saltation
Small pebbles and stones are bounced along the river bed.
Traction
Large boulders and rocks are rolled along the river bed.
Meanders
How are they made?
Water twists and turns around stones and other obstructions resulting in areas of slower and faster water movement.
The river starts to flow from side to side in a winding course but still in a relatively straight channel.
Water moving faster has more energy to erode. This occurs on the outside of the bend and forms a river cliff.
The river erodes the outside bends through corrasion, corrosion and hydraulic action.
Water moves slowly on the inside of the bend and the river deposits some load, forming a river beach/slip-off slope.
Continuous erosion on the outer bank and deposition on the inner bank forms a meander in the river.
The meander will migrate downstream and change shape over time.
Ox-bow Lakes
How are the made?
The river is meandering across the valley.
The river is eroding laterally (from side to side).
The river flows faster on the outside bends and erodes them.
The river flows slowly on the inside bends and deposits material so its course is changing.
Continual erosion and deposition narrows the neck of the meander.
Often during a flood the river will cut through the neck.
The river continues on its straighter path and the meander is abandoned.
New deposition seals off the ends and the cut-off becomes an oxbow lake that will eventually dry up.
Erosion
Solution
This is when sea water dissolves certain types of rocks. In the UK, chalk and limestone cliffs are prone to this type of erosion.
Attrition
This is when rocks that the sea is carrying knock against each other. They break apart to become smaller and more rounded.
Abrasion
This is when pebbles grind along a rock platform, much like sandpaper. Over time the rock becomes smooth.
Hydralic action
This is the sheer power of the waves as they smash against the cliff. Air becomes trapped in the cracks in the rock and causes the rock to break apart.
