rivers Flashcards
what is attrition?
when pieces of bedload (material carried by a river or seawater) are hit against one another. This causes them to break apart and become smaller and more rounded.
What is Hydraulic action?
Where the force of the water hits against the river or sea bed and banks and causes the rock to break off.
What is abrasion?
where pieces of rock are picked up by the river and hit against the bed or the banks - this wears them away.
What is solution?
Soluble rocks are dissolved by the water in the river (limestone and chalk in particular). They are carried along with the river.
What is suspension?
silt (sand , clay or other materials) are held in water. but not dissolved. The silt particles are then transported on with the river
What is saltation?
small sand or gravel particles bounce along the river bed, they will travel in the direction of the flow of water.
What is Traction?
Large rocks or large particles are dragged along the river bed by the current.
What is deposition?
When the sediment that a river is transporting is dropped. This happens in the middle and lower course of the river and in lower energy conditions
what are the reasons for deposition?
- increased amount of sediment in the channel
- reduced volume of water in the channel
- water becomes shallower
- the rivers mouth is reached
