Rivers Flashcards
What is the river course
The path of the river as it flows downhill
Where is the upper course
Closest to the source of the river
Where is the lower course
Closest to the mouth of the river
How do rivers form channels and valleys
- The ERODE the landscape
- They transport the material somewhere where it is deposited
- The shape depends on whether erosion or deposition has the most impact
Upper course properties
- Steep
- V-shaped valley, steep sides
- Narrow, shallow channel
Middle course properties
- Medium
- Gently sloping sides
- Wider, deeper channel
Lower course properties
- Gentle
- Very wide, almost flat valley
- Very wide, deep channel
Vertical erosion
- This DEEPENS the river valley, making it a V-SHAPED valley
- Dominant in the UPPER course of the river
Lateral erosion
- This WIDENS the river valley
- Dominant in the MIDDLE and LOWER courses
Name the four process of erosion
- Hydraulic action
- Abrasion
- Attrition
- Solution
Hydraulic action
The force of water breaks rock particles away from the river channel
Abrasion
Eroded rocks picked up by the river SCRAPE and RUB against the channel, wearing away.
Most erosion happens by abrasion
Attrition
Eroded rocks picked up by the river SMASH into each other breaking into smaller fragments.
The edges are rounded off as they rub together
Solution
River water DISSOLVES some type of rocks e.g. chalk and limestone
Name the four processes of transportation
- Traction
- Saltation
- Suspension
- Solution
Traction
Large particles (like boulders) are PUSHED along the river bed by the water FORCE
Saltation
PEBBLE sized particles are BOUNCED along the river bed by the water FORCE
Suspension
SOLUBLE materials DISSOLVE in the water and are CARRIED along
Solution
River water DISSOLVES some type of rocks e.g. chalk and limestone
When does deposition happen and why
- When a river drops eroded material
- Happens when a river slows down (loses velocity)
Why do rivers slow down and deposit material
- Volume of water falls
- Amount of eroded material in the water increases
- Water is shallower e.g. inside of a bend
- River reaches the mouth
What happens when a river is eroding and depositing material
Meanders and ox-bow lakes
Where are meanders found
In the middle and lower courses
Formation of a meander
- The water current flows faster on the outside of the bend, because the river channel is deeper (less friction to slow water down)
- More erosion on the outside of the bends, forming river cliffs
- Current is slower on the inside bend (channel is slower) More friction -> Slow water down
- Eroded material is deposited on the inside of the bend, forming slip-off slopes