Water on the Land Flashcards
What are the processes of erosion?
CASH:
- Corrasion/Abrasion
- The rivers load rubbing against the bed and the banks of the river
- Attrition
- The river’s load hitting against itself, breaking up into smaller pieces
- Solution
- Rock minerals dissolving into the water
- Hydraulic Action
- The sheer force of the water on the bed and the banks of the river
What are the processes of transport?
TSSS:
- Traction
- Large boulders roll along the river bed (most energy)
- Saltation
- Smaller pebbles bounce along the river bed
- Suspension
- Finer sand and silt are carried along in the flow of the river
- Solution
- Minerals dissolved in the river, cannot be seen (least energy)
When do rivers deposit materials?
When its volume or its speed decreases
What is material deposited by a river called?
Alluvium
What are the features of the upper course? (5)
- Greatest potential enery
- Vertical erosion
- V shaped valley - narrow and steep
- Interlocking spurs
- Not very habitable
What are the features of the middle and lower course? (4)
- Less potential energy
- Lateral erosion
- Wide and flat valley
- More habitable
What are the landforms of the upper course? (2)
- Waterfalls
- Gorges
How are waterfalls and gorges formed?
What processes of erosion are present in the formation of a waterfall?
- Hydraulic action erodes the less resistant rock
- Abrasion deepens the plunge pool
What are the landforms of the middle and lower course? (6)
- Meanders
- Ox-bow lakes
- Floodplains
- Levées
- Estuaries
- Deltas
How are slip-off slopes and river cliffs formed?
Slip-off slopes:
- The water has the least energy on the inside of a meander
- Sand and shingle are deposited, forming a slip-off slope
River cliffs:
- The water has the most energy on the outside of a meander
- The bank is eroded by abrasion causing a steep river cliff to form
How are ox-bow lakes formed?
- Erosion of the outside bend means the neck of a meander becomes narrower over time
- Eventually the neck is broken causing a straight channel
- Alluvium is deposited which seals of the old meander
What is a floodplain?
The wide flat area of land either side of the river in its lower course. When a river floods, it deposits its load as alluvium. Over many thousands of years, the alluvium builds up
How are levées formed?
When a river floods, the heaviest material is deposited closest to the river. This material builds up over many floods to build up natural walls on either side of the river
What is the river discharge?
The volume of water passing a point in the river at a particular time