Water on the Land Flashcards
Can you explain the process of hydraulic action?
The power of the volume of water moving in the river.
Can you explain the process of abrasion?
Occurs when larger load carried by the river hits the bed and banks, causing bits to break off.
Can you explain the process of attrition?
Load carried by the river knocks into other parts of the load, so bits break off and make the material smaller.
Can you explain the process of solution?
The dissolving of certain types of rock such as chalk and limestone by rainwater.
How do rivers tend to erode?
Vertical and lateral erosion.
Can you explain how the type of erosion changes as a river gets further down its course?
Vertical erosion becomes less important and lateral erosion takes over.
Can you explain the process of traction?
The rolling along of the largest rocks and boulders.
Can you explain the process of saltation?
The bouncing movement of small stones and grains of sand along the river bed.
Can you explain the process of suspension?
Small material carried within the river.
What is deposition?
Where the river dumps or leaves behind material that it has been carrying.
When is the largest material deposited?
In the upper course because it is the heaviest to carry.
When is the smaller material deposited?
Much further downstream because it is smaller so can be transported further.
When does the river drop some of its load?
When there is a fall in the speed of the water or the amount of water is less.
When is the speed of the water or the amount of water less?
When the gradient changes at the foot of a mountain or when a river enters a lake or sea.
What does a long profile show?
How the river changes its height along its course.
What does a cross profile show?
How the river’s valley changes shape downstream.
What are the characteristics of the upper course? 7
Mention: channel shape / which erosion / which erosion process / what transportation process / what is deposited / load size / valley shape
- shallow, narrow channel
- vertical erosion
- hydraulic action, abrasion and attrition
- some traction and saltation at high flow
- deposition of large material
- large load
- v-shaped valley
What are the characteristics of the middle course? 7
Mention: channel shape / which erosion / which erosion process / what transportation process / what is deposited / load size / valley shape
- wider, deeper channel
- some vertical erosion; lateral erosion more important
- hydraulic action less important
- suspension main transportation; saltation and traction still present
- deposition more obvious
- load size reduced
- v/u shaped valley
What are the characteristics of the lower course? 7
Mention: channel shape / which erosion / which erosion process / what transportation process / what is deposited / load size / valley shape
- widest, deepest channel
- less erosion; only a little lateral
- all erosion much less important
- suspension dominant
- deposition of fine material
- large amount of load, size now very small
- u-shaped valley
What landforms are a result of erosion? 2
- waterfalls
* gorges
What landforms are a result of erosion and deposition? 2
- meanders
* oxbow lakes
What landforms are a result of deposition? 2
- levees
* floodplains
How are waterfalls formed? 6
- hard rock (granite) overlies soft rock (sandstone)
- softer rock is eroded away faster than hard rock
- plunge pool is created
- plunge pool is deepened due to potholing which swirls around and rubs the bed and the banks
- an overhang forms as the softer rock is eroded further
- eventually the overhang collapses as it is unsupported
How is a gorge formed?
When the hard rock collapses because it is unsupported and the waterfall moves upstream.
How is a meander formed?
As the river erodes laterally, it forms large bends, and then horseshoe-like loops.
How is an oxbow lake formed? 4
- erosion causes a meander to narrow
- meander will eventually break off
- river now follows a straight path
- meander is cut and the river seals off the bend
How is a levee and floodplain formed? 2
- involve repeated flooding and the build-up of material during the period of flood
- under normal conditions, the river is contained within its banks and so no sediment is available to form them
What is precipitation?
Any source of moisture reaching the ground.