River processes and cross profiles Flashcards
What is erosion in the context of rivers?
The breaking down of rock particles being carried downstream by the river.
What is hydraulic action?
The force of the river against the banks that can cause air to be trapped in cracks and crevices, weakening the banks.
Define abrasion/corrasion.
The force of the water carrying stones and other materials that grind the bedload like a piece of sandpaper.
What is attrition?
Rocks being carried by the river smash together and break into smaller, smoother, and rounder particles.
Explain solution/corrosion in river processes.
Soluble particles are dissolved by weak acids in the water.
What are the four types of river erosion?
- Hydraulic action
- Abrasion/corrasion
- Attrition
- Solution/corrosion
What is solution in the context of river transport?
Minerals are dissolved in the water and carried along in solution.
Define suspension as a method of river transport.
Fine light material is carried along in the flow of the water.
What is saltation?
Small pebbles and stones are bounced along the river bed.
Explain traction in river transport.
Large boulders and rocks are rolled along the river bed.
What does a cross profile show?
A cross section of a river’s channel and valley at a certain point along the river.
Describe the erosion characteristics in the upper course of a river.
Increase in vertical erosion; the channel is shallow and narrow.
What happens to erosion as the river flows into the middle course?
Some vertical erosion occurs, but more lateral erosion; the channel is wider and deeper.
Characterize the lower course of a river in terms of erosion.
A lot less erosion with only some lateral erosion; the channel is at its widest and deepest.
When does deposition typically occur in a river?
When a river enters an area of shallow water or when the volume of water decreases.
