Understanding Rejuvination

Hi, everyone this is my first blog post and I am currently a student studying AS Geography!  I wanted to create this blog and this post to help other AS Geography students understand different topics. This is my first topic that I will be exploring:

What is rejuvination?


Rejuvenation is the renewal of a rives energy in response to a fall in base level. Basically, the base level is the lowest point in which the river can erode and it just refers to the sea. A fall in base level can be due to eusostatic sea level fall or isostatic rebound. As the base level has fallen due to an isostatic change or an eusostatic change, this means that the river is not in dynamic equilibrium. Dynamic equilibrium  refers to when the rate of erosion and deposition is balanced. Therefore, the river tries to reach a state of dynamic equilibrium by eroding to meet the new base level.

As the river erodes down to meet the new base level, there are several land forms that are formed in this process of rejuvenation.

River Terraces:


River terraces are formed when the river just erodes directly down to meet the new base level. They are remanents of former flood plains and river terracces occur when the river has abadoned the flood plain and this means that the floodplain can no longer be accessed. For example; London is on a river terrace.

There are two types:

Paired:
A paired river terrace is when, the terraces are on the same level on each side. So the river terraces look almost symmetrical on each side.This occurs when the fall in the base level is rapid and so this means that down cutting or erosion is rapid as a consequence. This means that there is not enough time for lateral erosion to take place and so only vertical erosion takes place, when paired river terraces are present.

Unpaired:

An unpaired river terrace is when, the terraces are on different levels on each side. They are the opposite to paired river terraces and they indicate a much gradual fall in base level. This means that the down cutting is not as rapid and lateral erosion ( hydraulic action and abrasion) as well as vertical erosion.

Another land form formed by rejuvenation is the Incised Meanders:

Incised meanders are formed when the river cuts down to meet the new base level and there are two types. 


Entrenched meanders

It occurs when there is a rapid fall in base level. Therefore, vertical erosion takes place and this causes them to have look deep cut, gorge like and have symmetrical cross section.    

Ingrown Meander


This is formed when the fall in the base level is more gradual and therefore lateral and vertical erosion takes place. They have asymmetrical cross section. An example of a place where the ingrown meander is present is the Grand Canyon.

An example of an ingrown meander- The Grand Canyon

Another land form which is formed as a result of rejuvenation is the waterfall.

Waterfalls

When a new base level has been created, rivers will often undercut the rock underneath to meet the new base level. This will cause a waterfall to take place.

The beautiful Vintgar Gorge in Slovenia

The last land-form are knickpoints:

Knickpoints


Knickpoints are caused when the river wants to down-cut to its new base level.But it is inhibited in down cutting because of a rock blocking its way and this causes a step in the long profile. However, with time this rock will be removed by erosion.

I hoped you liked my post and I hope to post on here regularly!

Sarah xxx