Flashcards in 4.6 - Landscapes And Processes Deck (16):
What is meant by the long profile of a river?
The long profile of the river shows you how the gradient changes over the different courses.
How does the river Eden’s landscape change along its long profile?
In the upper area it contains a steep gradient meaning a steep landscape and consists of v-shaped valleys, steep sides, narrow little channel, the velocity is the slowest and little discharge as sediment is large and squashed together in the upper course.
In the middle course it consists of a medium gradient, gentler sloping valley sides, wider and deeper channel, increasing discharge as sediment size is decreasing and the speed is also increasing.
In the lower course it consists of a gentle gradient, very wide and almost flat valley, very wide and deep channel, very large discharge, the fastest velocity and the sediment size is a mix of suspension and solution.
Compare Hydraulic Action with Abrasion.
Hydraulic Action is when Water is thrown at the edge of the cliff and water enters the cracks or throws other little rocks that chip the cliff edge. The water entering the cracks will increase the pressure and make the cracks larger over many cycles. When the cracks are to big, large rocks will fall off and over many cycles making a overhang.
Abrasion how ever is when a rocks are dragged/scraped/rub along the floor e.g a glaciar or sea/river and it erodes the floor removing small pieces as a result of the high force applying on it.
Weathering is the breaking down of rocks, soil, and minerals as well as wood and artificial materials through contact with the Earth's atmosphere, waters, and biological organisms.
What is biological weathering?
Is the breakdown of rock by living things, e.g. plant roots break down the rocks by growing into the cracks on their surface and pushing them apart.
Compare Traction and Suspension Transport.
Traction: Is when large rocks/rocks roll along the riverbed.
Suspension: The water flow carries silt and clay sized particles.
How is a waterfall formed?
Waterfalls form when the river flows over an area of hard rock above and soft rock bellow. The softer rock is eroded by hydraulic action and abrasion more than the harder rock creating a 'step' in the river. The 'step' get eroded more and more as water goes over it. The hard rock is then eventually undercut by erosion and becomes unsupported and then collapsing. The collapsed rocks then erode the soft rock in the plunge pool making it deeper and eroding at the back wall. Over time the hard rock collapses more which results in how much the river will retreat backwards.
How is a v-shaped valley formed?
The river (in the upper course) due its low discharge and gravitational potential energy it will only erode downwards. Then the sides of the river are slowly broken down through weathering processes. The weathered material is transported via gravity/rainfall/slope processes which then steepens the valley sides. This then creates v-shaped valleys.
How are interlocking spurs made?
In the upper course of a river most of the erosion is vertically downwards. This creates steep-sided, v-shaped valleys. This rivers in the upper course aren't powerful enough to erode laterally - they have to wind around the high hillsides that stick out into their paths on either side. The hillsides that interlock with each other as the river winds around them are called interlocking spurs.
How are meanders formed?
The current of the flow is fastest around the outside as it is the deepest resulting in less friction of the river flow. So more hydraulic action and abrasion occur on the outside of the bend which then form river cliffs. This then means the river will erode outwards and create large bends.
How are ox-bow lakes formed?
Ox-bow lakes can only form through a meander. Erosion through hydraulic action and abrasion causes the outside bends to get closer until there's only a small bit of land left between the bends. (called the neck) The river then breaks through the neck, usually during s flood, and the river flows along the shortest route missing the meander that was once there. After a long period of deposition it will eventually cut off the meander forming a ox-bow lake.
How are flood plains formed?
Flood plains are on either side of the river which are normally large pieces of land. When the river floods onto the flood plain, the water slows down and deposits the eroded material that it is transporting onto the flood plain which then build it up. (Makes it higher) Meanders migrate across the flood plain making it larger.
How are natural levees made?
During a flood eroded material is deposited over the whole flood plain. The heaviest material is deposited closest to the river channel, because it gets dropped first when the river slows down. Over time, the deposited material builds up, creating levees along the river edges of the channel.
How are deltas formed?
Rivers are formed to slow down when they meet the sea or a lake. This causes them to deposit the material that they're are carrying. If the sea doesn't wash away the material it builds up then the channel gets blocked up. This forces the channel to slip up into lots of smaller rivers called distributaries. This eventually then builds up the material so much the low-lying areas of land are called deltas.
Explain two ways climate, geology and slope processes change the river.
Climate: 1. Rivers in a wetter climate have a higher discharge because there's more water entering the river channel.
2. Transportation increases when there's a higher discharge because the river has more energy to carry material.
Geology: 1. Waterfalls have been formed when there is a layer of hard rock on top of soft rock.
2. Areas with softer rocks will experience more erosion - this adds more material to the rivers sediment load.
Slope Processes: 1. Mass movement e.g. Slumping, can add large amount of material to the rivers load.
2. Vertical erosion by rivers makes valley sides steeper, increasing the movement of material down the slopes.