Rivers Part1 Flashcards
3 main things rivers do
Erode-the land
Transport-rock particles and dissolved sediment
Deposit-the transported material
Rate of erosion is effected by:
Load-the heavier and sharper the load the greater chance of erosion
Velocity-greater velocity greater potential for erosion
Gradient-increased gradient increases rate of erosion
PH-solution increases where water is more acidic
Human impact-deforestation,dams and bridges interfere with flow of river and increasing rate of erosion
4 types of erosion
Abrasion
Attraction
Hydraulic action
Solution
Abrasion
eroded rocks picked up by river scrape and rubbed against the channel, wearing it away
Attraction
Eroded rocks picked up by the river smash into each other and break into smaller fragments. Edges rounded off as the rub together
Hydraulic action
Force of water breaks rock particles away from river channel
Solution
River water dissolves types of rock
4 types of Transportation are:
Traction
Saltation
Suspension
Solution
Traction
Large particles like boulders are pushed along the river bed by force of the water.
Saltation
Pebble sized particles bounded along the river bed by force of water
Suspension
Small particles like silt and clay carried along by water
Solution
Soluble materials dissolve in water and are carried along
Deposition
Is when a dive drops or leaves behind material that’s it’s been carrying
Long profile
A line representing course of a river from its source to its mouth where it begins and changes in height along its course
Cross profile
A line that represents what it would be like to walk from one side of a valley across the channel and up other side
Upper course of river
- steepest slope
- narrow stream
- rocky bed
- most erosion
- source
Middle course of river
- less steep
- quite wide stream
- less rocky
- erosion and deposition
Lower course of river
- flatter slope
- wide river
- smooth bed
- fasted flow
- river appears to move slowly
- deposition
- mouth
Meanders
Bends in the rivers course
Waterfalls
- Hard rock lies above soft rock
- soft rock erodes more quickly due to hydraulic action and abrasion
- Hard rock is undercut and overhangs as erosion of soft rock continues
- Plunge pool is created at base of waterfall
- Then hard rock collapses into plunge pool as can’t support its own weight
- Waterfall retreats upstream forming a steep sided gorge
- Process begins again
Outside of meander
Water is deeper, current flows faster
Force of water erodes and undercuts outside bend by abrasion forming steep bank called a river cliff
Inside bend of meander
Current is less strong encourages deposition
Oxbow lakes
- A bend in river forms called a meander
- Neck of meander gets narrower over time due to continued erosion on outer bend
- Due to continued erosion beck get narrower and during a flood water travels straight across making quickest route
- River deposits rock and soil cutting off the meander creating ox-bow lake.
