Water on the Land Flashcards
What is hydraulic action?
Erosion caused by the force of the river against the banks and beds as the pressure weakens and wears away rock.
When does abrasion occur?
When rocks carried along by the water cause the river beds and banks to wear/erode away.
Define ‘attrition’
The process by which rocks carried in the river smash into one another and break into smaller, smoother, rounder particles.
What is corrosion/solution?
When soluble particles (from the river beds/banks) are dissolved into the river.
Describe vertical erosion
Vertical erosion is the downward action of erosion that deepens the river channel and is dominant in the upper course due to increased gravitational pull.
What is lateral erosion and when is it most likely to occur?
The sideways action of erosion that widens the river channel and is most dominant in the lower course of the river.
Name the four processes of transportation
- Suspension
- Solution
- Traction
- Saltation
What is suspension?
When fine, light material is carried along in the river
How is solution created?
When minerals are dissolved in the water and carried along in solution
Define traction
Traction is when large boulders and rocks are rolled along the river bed
What is saltation?
Saltation is when small pebbles and stones are bounced along the river bed
The landforms that occur in the upper course of a river are …………. and ………….. They are created by ……………
The landforms that occur int he upper course of a river are waterfalls and gorges. They are created by erosion.
In the middle course of a river, notable landforms include …….. and ………..
These are created by ………….. and ………….
In the middle course of a river, notable landforms include meanders and oxbow lakes.
These are created by erosion and deposition.
Which river landforms will be present in the lower course of a river and how are they formed?
Levees and Floodplains are common in the lower course of a river and these are created by deposition.
Give some features of a lower course of a river (4)
- Wide and deep river channel
- Suspended sediment
- Deltas and estuaries
- Situated within predominantly flat land (flood plains)
Outline some features of the upper course of a river (4)
- Tributaries
- Narrow and shallow river channels
- Large angular bedload
- Steep valley sides
- Fast-flowing rapids (due to gravitational pull)
List some features of the middle course of a river (4)
- Tributaries
- Deeper and wider river channel than in the upper course
- Small angular bed load
- U shaped valley, more gradual relief of the land than in the upper course
erosion, undercut, overhang, plunge pool, abrasion, hydraulic action, retreat
Briefly outline the 6 main phases in waterfall formation, draw a labelled diagram if it helps
- When river flows over hard and softer rock, the softer is eroded more rapidly (creating a dip)
- Over time the dip becomes deeper amd eventually the harder rock is undercut (creating an overhang)
- Below the overhang, a plunge pool forms
- Overhanging rock is unsupported and will begin to crack and fall into the plunge pool.
- Pieces of are swirled around in the plunge pool, making it larger by abrasion and hydraulic action making it larger
- As overhang continues to fall off, the waterfall will retreat upstream.
How is a gorge formed?
As a waterfall retreats due to overhang collapsing into the river, a gorge is cut into the land.
What is a meander, when are they most likely to occur and why?
A winding curve or bend in a river, typical of the lower and middle course because there is a higher volume of water with more energy and** less friction** acting upon it. They are created by lateral erosion.
Describe the five main stages of meander formation
Try and include these terms: pools, riffles, hydraulic action, abrasion, river cliff, slip-off slope
- River flow weaves around sediment on the river bed, creating deeper pathways in some places (pools) and shallow areas where there is more sediment (riffles).
- The river flow will swing from side to side, around the riffles.
- The river bank on the outside of a bend in the river is increasingly eroded by hydraulic action and abrasion, creating a river cliff. Sediment is deposited on the inside of a river to form a slip-off slope.
- Meanders are perpetuated by helicoidal flow, when the water hits the outer bank it deposits eroded material on the inner bank.
- Over time, the bend will become tighter and end points, closer together.
Draw the hydrological cycle (there are 10 main processes)
List the 5 main features of a river
- Watershed
- The source
- Main river channel
- Tributary
- Confluence
What is a watershed?
The boundary of a river, any water falling outside of it will flow into another basin
In what unit is the volume of flowing water in a river measured?
Cumecs (cubic metres per second)
What does the bar and the line of a storm hydrograph show?
- The bar shows how a river responds to a period of rainfall
- The line shows how precipitation effects river discharge.
What is peak rainfall and peak discharge?
Peak rainfall: when rainfall is at it’s highest
Peak discharge - when river flow has reached it’s maximum
Define ‘lag time’
The period between peak rainfall and peak discharge