The River Valley
A Rivers Long Profile and Cross Profile Vary Over its Course
1) The path of a river it flows downhill is called its course.
2) Rivers have an upper course (closest to the source of the river), a middle course and a lower course (closest to the mouth of the river).
3) Rivers form channels and valleys as they flow downhill.
4) They erode the landscape - wear it down, they transport the material to somewhere else where its deposited.
5) The shape of the valley and channel chages along the river depending on whether erosion or deposition is having the most impact (is the dominant process).
6) The long profile of a river shows you how the gradient (stepness) changes over the different courses.
7) The cross profile shows you what a cross-section of the river looks like.
There are Four Processes of Erosion
1) Hydraulic action- The force of water breaks rock practicles away from the river channel.
2) Abrasion- Eroded rocks picked up by the river scrape and rub against the channel, wearing it away. Most erosion happens by abrasion.
3) Attrition- Eroded rocks picked up by the river smash into each other and break into smaller fragments. Their edges also get rounded off as they rub together.
4) Solution- River water dissolves some types of rock, e.g. chalk and limestone.