Rivers - Landforms Flashcards
1
Q
describe
v-shaped valley
A
steep sided valley, upper course
2
Q
explain
v-shaped valley
A
- vertical erosion
- load deepens the bed by abrasion
- steep sides bc loose material being washde downhill
3
Q
describe
interlocking spurs
A
- projections of high land that alternate from either side of a valley and project into the valley floor
- convex slope
4
Q
explain
interlocking spurs
A
it is the easiest path for the river to take, so it can avoid hard rock that it cannot erod
5
Q
describe
rapids
A
stretches of fast-flowing water tumbling over a rocky-shallow riverbed
6
Q
explain
rapids
A
- occurs bc there r angular rocks where there r bands of hard and soft rock
- this makes the riverbed uneven
7
Q
describe
waterfalls and gorges
A
- waterfalls: steep or vertical drop in the river, usually from considerable height
- gorges: steep sided rocky valley
8
Q
explain
waterfall and gorges
A
- the water flows over a band of hard rock and soft rock. due to differential erosion it erodes the soft rock faster, creating a dent in the bottom
- splash back from the falling water causes hydraulic action to weaken rocks behing (explain term hydraulic action)
- the unsupported hard rock breaks off. these rocks create a plunge pool
- the process repeats and creates a gorge
9
Q
describe
meanders
A
- large bends/curves in the channel
- river cliff and gentle slope
10
Q
explain
meanders
A
- helicoidal flow - a corkscrew movement
- top part of flow hits the outside bend and erodes it = rivercliff
- then flows to next inside bend and due to friction it deposits its load = gentle slope
11
Q
describe
ox-bow lakes
A
- crescent shaped lake cut off from meander
- lake will evaporate over time
12
Q
explain
ox-bow lakes
A
- meander neck becomes narrow
- river floods and goes straight thru the neck
- flood recedes so river goes back to normal. it floods again and again. new channel becomes established by the amount of floods and lateral erosion it becomes the main channel
- loop becomes detached, this sped up by more deposition
13
Q
describe
levees
A
- naturally raised banks
- can be artificially heightened
14
Q
explain
levees
A
- before flood river is normal
- during the flood the rivre deposits heavier load on the banks of the flood, finer stuff is deposited on the outerparts
- after many floods the levees build up
15
Q
describe
floodplains
A
- large, flat areas on sides of the river
- they regularly flood
16
Q
explain
floodplains
A
erosion
erodes any interlocking spurs
deposition
due to the river flooding many times it deposits silt over the land causing the floodplain to be slightly more raised
17
Q
describe
estuaries
A
- freshwater from river merges w/ saltwater from sea
- salt marshes might be there
18
Q
explain
estuaries
A
- when the waters meet, velocity decreases and deposition occurs
- mud builds up creating mudflats that can be seen at low tide
