model answer for meander formation?
- 0 votes
i would like a full model answer for meander formation for AQA for AS level as i have looked in many text books biut cannot seem to undertsand. any help ASAP will be helpful. THANKS
- 1 vote
Hey there, I would write this:
Meanders form where alternating pools and riffles develop at equally spaced intervals (the distance between the pools is roughly 5-6 times the width of the river bed). The river channel is deeper in a pool so it's more efficient. However, energy is lost as the river flows over a riffle because of friction. The spacing between these riffles and pools causes the river's flow to become uneven and the maximum flow is directed to one side of the channel. Turbulence increases around pools as the water speeds up, so the flow of water begins to twist and coil. This causes a corkscrew-like movement in the river called helicoidal flow. The helicoidal flow transports sediment from the outside bend to the inside of the next bend. Eventually, a river cliff is formed on the outside bend due to erosion and a slip-off slope on the inside bend caused by deposition.
- 0 votes
there are no model answers in the text book which is why you won't find one :). You basically need to say about riffles and pooles and that sequence, and basically the pages on how meanders and oxbow lakes are formed. You would then need to add in that there is no clear conclusion on how they are formed ie: whether the riffles and pooles come first then the meander or the meander, then riffles and pooles. As there is no clear formation of how they are formed, its a lot easier to flesh out as you can say "well here is the riffles and pooles" and then "here is a meander" then you can be like "well there is no clear distinction on which comes first as scientists are still unable to prove it in a science lab, so it is open to investagation, and at this moment, a form of nature" etc etc :) hope it helped
- 0 votes
yeah that's right :) you also wanna add in that they are found in the middle - lower streches of a river due to downward cutting being changed into lateral erosion as the river gets lower from the source and tries to reach base level again. The energy changes the cutting styles as there is no more potential energy with gravity wanting to act on it, like there is up in the upper stretches so it uses the energy that would otherwise have been used for downward cutting (creating the v-shape valley) to cut laterally instead, creating the formation of meanders.