AQA Geography A-level predictions GEOG1 12/5/15

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AqibKhan19
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Hi, what are people's predictions for the aqa a-level geography exam, topics: rivers coasts population and health?
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mark8999
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meanders, and also a load of bullsh**
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irMike
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River landforms, probably meanders.

Whilst we're on the topic, does anybody know exactly how meanders are formed? If the question came up I'd answer it like so:

1) Alternating layers of sediment, water tries to avoid the sediment, flowing around it.
- This creates pools (Deep water) and riffles (Shallow water)
2) Over the pools, the river has more energy, so it erodes one of the banks, depositing the material on the inside bank.
- Increasing the rivers sinuosity
3) The turbulence of the water causes it to twist and coil into a corkscrew like movement called Helicoidal flow, making the water carry sediment from the outer/concave bank, into the inner bank, maintaining the meander downstream.

That's all I know, does anybody knows what I'm missing? Or if that would be a good enough answer for most of the marks?
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mark8999
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Meanders

Meanders are bends in a river that form as a river’s sinuosity increases. The sinuosity of a river is a measurement of how much a river varies from a straight line. It’s a ratio between the channel length and displacement (straight line distance) between two points in the river’s course:

Sinuosity=Channel LengthDisplacement


A sinuosity of 1 means that the channel is perfectly straight. A sinuosity greater than 1 means that the river meanders.
Meanders develop when alternating riffles & pools form along a river channel. A riffle is a a shallow section of a channel while a pool is a deep section. These riffles and pools develop at equal points along the river channel with each pool being about 5× the length of the channel.
In a pool, the channel is more efficient, while at a riffle, the channel is less efficient. This causes the flow of the river to become irregular and the maximum flow is concentrated on one side of the river. This increases erosion on one side of the river and increases deposition on the other causing the river’s channel to appear to bend. Erosion is greatest on the outside bend and deposition is greatest on the inside bend
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AqibKhan19
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a meander is a winding bed in a river typically in the middle course of the long proifile because wben veritcal erosion is replaced by lateral eroision.

stage 1: in low flow conditions, staright river beds have bars of swediment on thier beds. flowing water weaves around these bars of sediment this creates deeper pathways where most of the water flows called pools and shallower areas where where less water flows called riffles. each spaced 5-6x the width of the river bed. this causes the river flow to swing from side to side.

stage 2: due to the centrepatal force the thalweg of the river (line of fastest flow) is towards the outside, this causes undercutting and creates landforms such as river cliffs due to the abrasion and hydraulic action. where veloicity is lower, on the inner bank, material is deposited, this forms pointbars. due to these two factors: erosion and deposition the meander itself doesnt get wider. but these processes give it its distictive asymentrical shape

stage 3: meanders are perpetuated (carried on) through a process called helicoidal flow. as the surface flow of the water hits the outerbank of the river bed it corckscrews, flows along the width of the river bed, then depositis erodded material on the rivers inner bank, further increasing the depoisition, increasing the size of the pointbar.

stage 4: erosion is greatest beyond the miidle of the bend in the meander, causing the meander to migrate downstream over time.

stage 5: oxbow lakes are formed when the neck of the meander is flooded, depoisiton cuts of the loop during flooding.


hope this helps
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AqibKhan19
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This much detail is obviously only needed if the question was for a 15 marker. for shorter answers not a much detail will be needed
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irMike
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(Original post by AqibKhan19)
a meander is a winding bed in a river typically in the middle course of the long proifile because wben veritcal erosion is replaced by lateral eroision.

stage 1: in low flow conditions, staright river beds have bars of swediment on thier beds. flowing water weaves around these bars of sediment this creates deeper pathways where most of the water flows called pools and shallower areas where where less water flows called riffles. each spaced 5-6x the width of the river bed. this causes the river flow to swing from side to side.

stage 2: due to the centrepatal force the thalweg of the river (line of fastest flow) is towards the outside, this causes undercutting and creates landforms such as river cliffs due to the abrasion and hydraulic action. where veloicity is lower, on the inner bank, material is deposited, this forms pointbars. due to these two factors: erosion and deposition the meander itself doesnt get wider. but these processes give it its distictive asymentrical shape

stage 3: meanders are perpetuated (carried on) through a process called helicoidal flow. as the surface flow of the water hits the outerbank of the river bed it corckscrews, flows along the width of the river bed, then depositis erodded material on the rivers inner bank, further increasing the depoisition, increasing the size of the pointbar.

stage 4: erosion is greatest beyond the miidle of the bend in the meander, causing the meander to migrate downstream over time.

stage 5: oxbow lakes are formed when the neck of the meander is flooded, depoisiton cuts of the loop during flooding.


hope this helps
Brilliant! Thanks
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AqibKhan19
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No worries!
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12g
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For anyone doing cold environments, do you think the 15 marker will be on tundra/antarctic environments? Because they have done them 3 times in a row already :/
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AqibKhan19
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Sorry can't help you there, don't do cold environments but it seems unlikely if it's been asked three times already, but I'd recommend learn the key points anyway

hope that helps
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