Definition: |
A river is said to be rejuvenated when its base level is lowered.
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Keywords
- Isostatic change - When land moves up or down relative to the sea level due to crustal movements.
- Eustatic Change - A rise or fall in sea level due to the growth or shrinking of an ice cap.
- Knickpoint - The point in a river channel where there is a sharp change in slope gradient.
- Incised meander - An unusually deep river meander due to the river downcutting as a result of an uplift in the land.
- Graded Profile - A graded stream has a long profile that is in equilibrium with the general slope of the landscape.
Causes of Rejuvenation
A river rejuvenates when there is an increase in gravitational potential energy. It causes the river to erode its bed vertically to achieve equilibrium with the slope of the landscape. A basic way to think about why rejuvenation is necessary is that a river's natural long profile is a concave curve; steeper at the start and gentler towards the end. When this curve is disturbed by a movement in sea level, the river erodes its way back to a course that resembles a concave curve.
Types of rejuvenation include:
A river rejuvenates when there is an increase in gravitational potential energy. It causes the river to erode its bed vertically to achieve equilibrium with the slope of the landscape. A basic way to think about why rejuvenation is necessary is that a river's natural long profile is a concave curve; steeper at the start and gentler towards the end. When this curve is disturbed by a movement in sea level, the river erodes its way back to a course that resembles a concave curve.
Types of rejuvenation include:
- Dynamic Rejuvenation: A result of isostatic change, when land rises due to faulting and the river must begin active downward erosion.
- Eustatic Rejuvenation: Result of global sea level change because of ice caps melting or forming. When sea levels fall, eustatic rejuvenation affects the mouth of the river, and the river erodes it's way back towards its source, creating waterfalls, rapids and incised meanders.
- Static Rejuvenation: Caused by a decrease in load or an increase in run-off, usually in the upper course of the river after glaciers have melted. Leads to valleys getting deeper.