4.6 Landscapes And Processes Flashcards
What is meant by the long profile of a river?
A long profile shows the height of the river as it flows from the source to the mouth
How does the river Eden’s landscape change along its long profile
In the upper course, the river channel is very narrow and shallow with a steep sided valley. The channel has a high gradient with low slow discharge. The sediment carried is large and angular. By the time you get to the lower course the valley is very wide and flat, the channel is very wide and deep. It has a very low gradient and there is lots of fast discharge. The sediment is fine and well rounded
Why does the river Eden’s landscape change like this?
Weathering on the valley sides slowly change the shape of the valley and as more tributaries join together, the discharge increases
Compare hydraulic action with abrasion
Hydraulic action is when water and air are forced into cracks in the river and forcing them wider while abrasion is when rocks in the river knock against the bed, wearing it away
Define weathering
When rocks scrape and smash about causing erosion of rock
Compare freeze thaw and biological weathering
Freeze thaw is when water get into cracks and at night the water freezes and expands causing the rock to get bigger while biological weathering is when roots or animals dig into the ground breaking it up
Compare traction with suspension transport
Traction is when large particles of rock bounce along the river floor downstream, while suspension is when small particles float in the river and are carried downstream
Explain the stages and processes responsible for waterfall formation
1) Waterfalls occur when more resistant rock lies over a layer of softer rock that gets eroded very quickly, forming a steep drop
2) Over time the rivers bedload swirls at the bottom and eventually a plunge pool is formed
3) The back wall of the waterfall is soft rock and erodes back quickly forming an overhang of hard rock.
4) This overhang becomes unstable and eventually collapses which leads to further erosion of the soft rock
5) As the waterfall erodes back, the walls either side of the waterfall stay forming a gorge.
Explain the stages and processes responsible for V-shaped valleys and interlocking spurs
1) in the upper coucours most erosion is vertically downwards, which created v-shaped valleys
2) the river isn’t very powerful here so cant erode through mountains so they have to wind around them.
3) the hills that interlock as the river winds around them are called interlocking spurs
Explain the stages and processes responsible for meanders
1) the current is faster on the putside of the bend as it is deeper
2) so more erosion takes place on the outer bend forming river cliffs
3) the inside bend has a slower current as it is shallower so more is deposited there making a slip-off slope.
Explain the stages and processes responsible for ox-bow lakes
1) erosion causes the outside bend of a mesnder to get closer until there is just a neck left
2) during a flood, the river breaks through this area of land
3) deposition eventually cuts of the meander forming an ox-bow lake
Explain the stages and processes responsible for flood plains
1 )floodplain is the wide valley floor either side of a river. When it flood the water slows down and deposits material on the floodplain making it higher. Meanders make the floodplain wider and the deposition on slip-off slopes also builds it up
Explain the stages and processes responsible for levees and deltas
1) during the flood of a river, material is deposited on the floodplain but the heaviest is dropped on the edge of the channel. As this builds up it creates a raised embankment either side of the channel.
2) rivers have to slow down when the reach the mouth so they deposit lots of material around them. If this is not washed away, it builds up blocking the channel and forming distributaries. When the land builds up so much a low-lying delta is formed.
Explain two ways climate, geology and slope processes change the landscape
Climate change: wetter climates creates more discharge which means more erosion of the channel.
This also helps form v-shaped valleys
Geology:rivers in areas of resistant rock have less erosion and sediment load so will have steep sides, whereas areas with softer rock will have more gentle sloping sides
Slope processes: slumping makes river wider, vertical erosion makes it steeper with more material moving down
Compare a flashy and subdued hydrograph
A flashy hydrograph has a higher peak discharge and a lower lag time than a subdued hydrograph. A subdued hydrograph has a longer rising limb than a flashy one
