What is the length, depth and width of a river affacted by?
Erosion.
1 of 25
What causes erosion of a river?
The energy pf a river flowing downhill causes erosion.
2 of 25
What parts of a river can be eroded?
The bed (bottom) of a river and the banks (sides) of a river can be eroded. This makes the river longer, deeper and wider.
3 of 25
What is headward erosion?
This is erosion that makes a river longer. It happens near a rivers source and throughflow and surface runoff cause erosion at the point the water enters the river channel (valley head).
4 of 25
What is vertical erosion?
Vertical erosion happens in the upper stages of a river and causes the river to become deeper.
5 of 25
What is lateral erosion?
Lateral erosion makes the river wider. It happens in the middle and lower stages of a river.
6 of 25
Name the 5 mains ways in which river erosion happens.
Hydraulic action, Abrasion (corrasion), Attrition, Cavitation and Corrosion.
7 of 25
What is Hydraulic action?
The pressure of the water breaks rock particles away from the bed and banks of a river. Its strongest in rapid and waterfalls, and during floods.
8 of 25
What is Abrasion (corrasion)?
eroded pieces of rock in the water scrape and rub against the river bed and banks, removing material. Most erosion of the river beds and banks happen by abrasion.
9 of 25
What is attrition?
This is where eroded rocks smash into each other and break into smaller fragments. They 'round off' as they smash together. This doesnt erode the bed and banks, it just makes the paricles of rock in the river smaller.
10 of 25
What is Cavitation?
This is where air bubbles in turbulent stretches of water implode causeing shockwaves that break pieces of rock off the banks and bed.
11 of 25
What is corrosion?
This is the dissolving of rock by chemical processes. Carbon Dioxide dissolves in water to form a weak acid, which reacts with rocks like limestone and chalk, breaking them down.
12 of 25
What is the eroded material carried in a river called?
This is called the Load.
13 of 25
What four ways can material be carried in a river?
Solution, Suspension, Saltaion and Traction.
14 of 25
What is solution?
This is when substances that can be dissolved, are carried along in the water. For example - Limestone.
15 of 25
What is suspension?
Very fine material, like silt and clay particles, is whipped up by turbulence and carried along in the water. Most eroded material is transported this way.
16 of 25
What is saltation?
Larger particles, like pebbles or gravel, are too heavy to be carrie din suspension. Instead, the force of the wate cayses them to bounce along the river bed.
17 of 25
What is traction?
Very large particles, for example boulders, are 'pushed' along the river bed by the force of the water.
18 of 25
What is deposition?
Deposition happens as a result of a river lossing energy. When is slows down, it loses energy and drops some of it load.
19 of 25
What can the speed of a river be reduced by?
Reduced rainfall, Increased evaporation, Friction, wideness of the channel and when the water reaches the mouht of the river.
20 of 25
What is the capacity of a river?
This is the total amount of material a river can carry. This is measured in voulme, weight or mass.
21 of 25
What divides the load of a river into different categories?
The particle size.
22 of 25
What is the competence?
This is the maximum particle size that a river is capable or transporting at a given point.
23 of 25
What is the Hjulstróm curve?
This is a graph that shows the relationship between river velocity and competence.
24 of 25
What is competence affected by?
This is affected by the amount of energy the river has, which is related to its velocity. Generally, the greater the velocity, the greater the energy.
25 of 25
Other cards in this set
Card 2
Front
What causes erosion of a river?
Back
The energy pf a river flowing downhill causes erosion.
Comments
No comments have yet been made