TOPIC 1B: River landscapes and processes 🌊 Flashcards
What type of gradient does the upper course of a river have?
Hint: begins with s
- the upper course of a river, has a steep gradient
What type of gradient does the lower course of the river have ?
Hint: what letter begins with g?
Gentle gradient
What type of gradient does the middle course of a river have?
Hint: M
- the middle course of a river, has a medium gradient
What are the two types that erosion can be?
Hint: vertical + _______.
- vertical
- lateral
Can you explain what lateral erosion does?
Hint: widens the _____ valley and
- lateral erosion, widens the river valley [and channel], during the formation of meanders.
- ; [it’s dominant in the middle and lower course].
Can you explain what vertical erosion does?
Hint: deepens the … valley
Hint #2: what shape?
- deepens river valley (and channel) making it v-shaped.
- [dominant in the upper course of the river + high turbulence causes the rough, angular particles to be scraped along the river bed, which causes downwards erosion].
Can weathering shape river valleys ?
Yes
Suggest how mechanical weathering could shape a river in the valley course [4]
Hint: freeze-thaw, WIRE
- water in the cracks of rocks freezes and expands- which puts pressure on the rock.
- water thaws, and it contracts and releases pressure on the rock
- repeated freezing + thawing widens crack, and causes rock to break up.
- therefore this makes rockfall more likely, and this changes the shape of the valley side.
What are two ways, that mass movement can influence river landscapes ? [3]
Hint: undercutting of a slope
- mass movement, is when gravity causes the movement of material down a slope
- a river could erode the base of a valley, and could cause undercutting of slope.
- mass movement can add large amounts of material to river’s load.
What are four reasons, why rivers slow down and deposit material? [4]
Hint: shallower
- Any from:
- volume of water in the river falls
- amount of eroded material in the water increases.
- water is shallower [e.g- inside of a bend]
- the river reaches its mouth.
Fill in the gaps:
Landscapes with more resistant rocks tend to have _______ valley sides.
Landscapes with less resistant rock tend to have gentle ______ valley sides.
- Landscapes with more resistant rocks tend to have steeper valley sides.
- Landscapes with less resistant rock tend to have gentle sloping valley sides.
Explain how a waterfall is formed. 💧
Hint: quicker than, undercut, plunge, collaspes, retreats, gorge
- soft rock is eroded quicker than the hard rock and this creates a step.
- and as erosion continues, the hard rock is undercut- which forms an overhang.
- abrasion and hydraulic action then erode to create a plunge pool
- and over time, this gets bigger, increasing the size of the overhang until the hard rock is no longer supported and it collapses.
- this process continues and the waterfall retreats upstream.
- and finally, a steep-sided valley is left where the waterfall once was. [a gorge]
Explain how interlocking spurs are formed [3]
Hint: upper course, harder to erode and
- interlocking spurs are formed because:
- in the upper course, there is more vertical erosion
- the river cuts down into the valley, and if there are areas of hard rock which are harder to erode, the river will bend around it.
- This then creates interlocking spurs of land [which link the land together]
Explain how meanders are formed. [5]
Hints: current of water, high-energy environment, low energy environment, eroded material deposited + material builds up.
- the current of the water is faster on the outside of the bend because the river channel is deeper
- this means the outside of the bend is a high-energy environment, which means more abrasion and hydraulic action take place. (This forms steep-sided river cliffs).:
- inside of bend is a low-energy environment + the current is slower because the river channel is shallower.
- So eroded material deposits on inside of bend
- over time, material builds up to form a point bar
Explain how an oxbow lake is formed [3]
Hint: outside bends, breaks through, deposition cuts off…
- an oxbow lake is formed because:
- erosion causes outside bends to get closer, until there’s only a small bit of land left
- the river then breaks through this land (typically during a flood), and the river then flows along the shortest course
- ; deposition, now eventually cuts off the meander and this forms an oxbow lake.
