River Rejuvenation and Landforms
Describe and explain the formation of landforms resulting from rejuvenation. (15 marks)
River rejuvenation is caused by a drop in sea level, which means a river has further to go to get to the sea and therefore has more energy. This means that the river stages all go back one. Isostatic shift is when the land rises relative to the sea level, caused by the melting of ice sheets. Eustatic shift is when the sea level falls relative to the land, caused by the creation of ice sheets.
A landform which is formed through river rejuvenation is knick points. A knick point is a sudden break or irregularity in a river long profile where gradient increases suddenly. When the base level falls the river begins to cut down to its new base level with renewed energy. These will move back upstream by headward erosion. A knick point is often marked by a waterfall. Another landform that is formed is river terraces. They mark the level of old floodplains which is now left at a higher level after a river has been rejuvenated. River terraces can form by dynamic or climatic causes. The process of river rejuvenation gives the channel more gravitational potential energy which allows more vertical erosion. This allows the river to cut its channel down through the former floodplain. River terraces can either be paired or unpaired. Paried river terraces are at the same level either side of the channel. Compared to unpaired river terraces which have slower cutting and can be at different levels either side of the channel.Incised meanders are another landform that is formed through rejuvenation. Meanders may become incised or deepened. Rejuvenation provides more energy for vertical erosion. It is this increased vertical erosion which cuts large scars into the landscape. There are two types of incised meanders; entrenched and ingrown. Ingrown meander occurs when the vertical erosion is occurring at a slow rate; this allows some lateral erosion too. Here, the outer bends of the meander
River rejuvenation is caused by a drop in sea level, which means a river has further to go to get to the sea and therefore has more energy. This means that the river stages all go back one. Isostatic shift is when the land rises relative to the sea level, caused by the melting of ice sheets. Eustatic shift is when the sea level falls relative to the land, caused by the creation of ice sheets.
A landform which is formed through river rejuvenation is knick points. A knick point is a sudden break or irregularity in a river long profile where gradient increases suddenly. When the base level falls the river begins to cut down to its new base level with renewed energy. These will move back upstream by headward erosion. A knick point is often marked by a waterfall. Another landform that is formed is river terraces. They mark the level of old floodplains which is now left at a higher level after a river has been rejuvenated. River terraces can form by dynamic or climatic causes. The process of river rejuvenation gives the channel more gravitational potential energy which allows more vertical erosion. This allows the river to cut its channel down through the former floodplain. River terraces can either be paired or unpaired. Paried river terraces are at the same level either side of the channel. Compared to unpaired river terraces which have slower cutting and can be at different levels either side of the channel.Incised meanders are another landform that is formed through rejuvenation. Meanders may become incised or deepened. Rejuvenation provides more energy for vertical erosion. It is this increased vertical erosion which cuts large scars into the landscape. There are two types of incised meanders; entrenched and ingrown. Ingrown meander occurs when the vertical erosion is occurring at a slow rate; this allows some lateral erosion too. Here, the outer bends of the meander