Rejuvenation Flashcards
What are isostatic changes?
Changes in the level of the land in relation to the sea level.
What are eustatic changed?
Changes in the sea level in relation to the land level.
Rejuvenation causes what two things to be increased?
- The rivers potential energy.
* The rivers capacity to erode (caused by the potential energy increase).
When rejuvenation happens, what does a river have to adjust to?
The river has to adjust to its new base level.
How does the river adjust to its new base level when rejuvenation is caused?
It does it from the sea and progressively inland.
When rejuvenation happens, what FIVE landforms can be caused?
Waterfalls Rapids Incised meanders Knick points River terraces
What is the potential energy of a river?
The amount of energy a river could have, dependent on the altitude of the source in relation to the rivers base level.
What are the two types of energy a river can have?
Potential and kinetic energy.
Describe what the kinetic energy of a river is.
Generated by the flow of a river, which converts the rivers potential energy into moving energy.
Define what river terraces are.
Narrow and flat pieces of ground that run parallel to the river on either side of it and above the current floodplain level. Usually created by a fall in base level.
What are river terraces usually caused by?
A fall in base level.
Finish the sentence. A river terrace is a remnant of…
A former floodplain thee been left with w higher level after the rejuvenation of a river.
Describe the process of a river terrace forming.
When rejuvenation takes place, the river renews its down cutting power and sinks its new Channel into a former floodplain and the old floodplain (river terrace) is left above the present river level.
When a river is rejuvenated, what is renewed?
The rivers power of down cutting in the form of vertical erosion power.
After terraces have been formed, how can they be cut back?
They can be widened by the river laterally eroding.
What can cause terraces to form beneath old river terraces?
Renewed rejuvenation.
Renewed rejuvenation can cause what?
More river terraces to form beneath the old ones.
Identify a river that has river terraces by several stages of erosion.
The river Thames.
Describe two practical human uses for river terraces.
- they can provide practical flood shelter in the rivers lower course.
- can be natural route ways for roads and railways.
Describe a place where river terraces have been used as natural tour ways for roads and railways.
The built up areas of Oxford and London are mostly located on the river terraces of the River Thames.
Define what an incised meander.
A meander that’s cut deeply into the floodplain of a river, causing steep cliff like banks. The river is formed by river rejuvenation.
Describe how the river is left when an incised meander is formed in the river.
The river level is left far below the former floodplain level.
What needs to happen for any type of incised meander to form?
A river needs to keep its meandering course as vertical erosion in the river increases.
What are the two types of incised meander that can be formed in a river by rejuvenation?
- entrenched meander
* ingrown meander
What are the three key features of any valley of an incised meander?
^deep
^steep sided
^wide valleys
An ingrown meander is formed when there is _______ incision and _______ erosion.
Slow incision
Lateral erosion
An ingrown meander has an ___________ valley.
Asymmetrical.
Describe the shape of the bends of an ingrown meander.
The outer bends has steep cliffs and re inner bends had a gentler slip off slope.
The outer bends of an ingrown meander has _______cliffs whereas the inner bend has a _______ slip off slope
INGROWN MEANDERS
Outer bend has steep cliffs
Inner bend has a gentler slip off slope
What is the nature of the incised meander formed mainly determined by?
The rate at which vertical erosion is ensuing in when rejuvenation of the river takes place.
What are entrenched meanders said to look like?
They have a Gorge like appearance.
Explain the criteria for an entrenched meander to form.
- rapid incision.
- vertical erosion or down cutting dominates.
- low level of lateral erosion.
An entrenched meander gives a __________ valley.
Symmetrical.
What are the shape of the sides of an entrenched meander?
They are steep sided valleys that are more symmetrical than the sides of an ingrown meander.
Define what a knick point is.
Usually marked by Rapids, knick points are caused by rejuvenation and are a sudden break in the gradient in the long profile of a river.
Most knick points are caused by ________.
Rejuvenation.
As well as rejuvenation, what other thing can cause a knick point within a river?
Rock type variation.
Some knick points are ______ _______. E.g; waterfalls.
Sharply defined.
When are knick pints formed?
Where old and new profiles of the river join.
The knick point recedes at a rate that’s dependent on what?
The resistance of rock.
Explain how a knick point is formed.
When a river rejuvenates, the new base level adjustment begins at the sea and works it’s way up the course- the river gains more downcutting power which encourages long poor file adjustment and the KP is formed where the old and new profiles join.
Define what rejuvenation is.
An increase in the energy of a river, caused by either a fall in sea level relative to the level of the land (eustatic change) of a rise of the level of the land in relation to the sea level (isostatic change).
