Landforms Flashcards
1
Q
How does a meander form?
A
- turbulent flow leads to formation of deeper pools + shallower riffles causing thalweg to flow from side to side
- causes helicoidal flow:
- erodes outer bends of meander, called undercutting, due to higher pressure, forming a river cliff
- deposits material on inner bends, due to lower pressure, forming a river beach/point bar
- continuous erosion on outer banks + deposition on inner banks forms meander
2
Q
How does a waterfall + gorge form?
A
- river flows over area of hard + soft rock
- soft rock erodes quicker creating a step
- soft rock beneath hard rock erodes causing undercutting forming an overhang that eventually collapses into plunge pool: deepening it
- process repeats causing waterfall to retreat upstream creating a gorge
3
Q
What may gorges be formed as a result of?
A
- retreat of river
- antecedent drainage
- glacial overflow
- collapse of underground caverns
4
Q
How do levees + floodplains form?
A
- river bursts its banks
- water quickly loses velocity so coarse material rapidly deposited near channel edge
- deposits build up forming embankments (levees)
- annual flooding builds up floodplain
5
Q
How does an oxbow lake form?
A
- during flood, erosion on a meander inc.
- river breaks through creating steeper channel
- over time old meander closed off by deposition forming oxbow lake
6
Q
How does a delta form?
A
- where river flows into sea (estuary): rate of deposition > rate of erosion
- grow outwards + benefit from flocculations (opposite charges of fresh + salt water cause clay particles to clump + be deposited)
- e.g. Mississippi into Gulf of Mexico
[diagram]
7
Q
What are the diff. types of delta?
A
- arcuate: longshore drift affects shape - stays smooth, fan shape (e.g. R. Nile)
- cuspate: pointed, foot shape - caused by opposing currents (e.g. Ebro)
- birds foot: lots of deposition + grows along pattern of river
