TO START - All of the following have something in common…

1. TO START - All of the following have something in common… incised meander river terraces They are all landforms that are created by rejuvenation knickpoint waterfall

2. WHAT IS OUR LEVEL OF UNDERSTANDING OF THE FOLLOWING?

3. WHAT IS OUR LEVEL OF UNDERSTANDING OF THE FOLLOWING? Isostatic change energy which something has as a result of its position the lowest point to which erosion can take place Eustatic change a ‘side elevation view’ of a rivers gradient which is in a state equilibrium (balance) Graded profile a deep steep-sided bend formed by the severe downwards erosion of an existing bend Knickpoint a location in a river or channel where there is a sharp change in channel slope Rejuvenation Incised Meanders A change in the level of the local land mass due to some factor River Terraces A step/level in an old flood plain that has been left perched on the side of a river valley. Potential energy the process whereby the base level that a river is flowing down to is lowered Kinetic energy A change in global sea levels due to some factor Base Level the energy an object possesses because of its motion

4. Answers Isostatic change A change in the level of the local land mass due to some factor A change in global sea levels due to some factor Eustatic change a ‘side elevation view’ of a rivers gradient which is in a state equilibrium (balance) Graded profile a location in a river or channel where there is a sharp change in channel slope Knickpoint Rejuvenation the process whereby the base level that a river is flowing down to is lowered a deep steep-sided bend formed by the severe downwards erosion of an existing bend Incised Meanders River Terraces A step/level in an old flood plain that has been left perched on the side of a river valley. energy which something has as a result of its position Potential energy Kinetic energy the energy an object possesses because of its motion Base Level the lowest point to which erosion can take place

5. OBJECTIVES: • To define the term REJUVENATION… • To describe and explain this process using the other terms given above. • To introduce the EROSIONAL features produced by REJUVENATION.

6. The long profile after REJUVENATION The river will erode down downwards due to gained GPE (so far upstream – this point is a knickpoint) A graded profile before REJUVENATION

7. So, Rejuvenation… A river is said to be _______ when the ____ _____ that it is flowing down to is ______. This can happen by ______ of land, or by a sea or lake that it is flowing into becoming ______. That makes the river suddenly start eroding its bed vertically (_________) faster as it gains ________ ______ energy. This is due to the river suddenly having an increased _____ to fall downhill to reach ____ ______. This causes ______ to cut down as ______, stretches of river that are much faster and ______ cut down sharply into existing ______ ______. The main causes of this process of rejuvenation are: ______ change –land ______ relative to the _____. This could be due to the sudden shunting up of land at or near a plate ______, associated with an ______. The ______ earthquake of 2005 resulted in an area of land being uplifted by 10m. The land could also rise due to a ______ effect. This is currently happening in the UK, where north west ______, which was previously covered in ice for thousands of years, is now rebounding back at a rate of per year (The south east of ______, which is obviously joined to it is ______ down as a result of this).

8. ______ change – sea ______ relative to the ______. One of the most common ways for this to happen is during colder periods called ______. Water is ______ ____as ____ on the land (ice caps at the ______, glaciers in the ______). ______ water is released back into the oceans, meaning that sea level falls. In both cases, water now has ______ to fall, meaning more ______ power. So existing flood plains and ______ ______ are ______ into due to these new ______ levels. The river is changing its ______ ______, sometimes called ______. This starts at the ______ of the river and then moves ______, basically because the change took place at the mouth. The limit of the regrading is marked by a ________. Upstream of this point the original graded profile is unaltered. Here there is likely to be a sudden change in _______ or even a _______.

9. A river is said to be rejuvenated when the base level that it is flowing down to is lowered. This can happen by uplift of land, or by a sea or lake that it is flowing into becoming lower. That makes the river suddenly start eroding its bed vertically (downcutting) faster as it gains gravitational potential energy. This is due to the river suddenly having an increased height to fall downhill to reach sea level. This causes meanders cut down as gorges, stretches of river that are much faster and terraces cut down sharply into existing flood plains. The main causes of this process of rejuvenation are: Isostatic change –land rising relative to the sea. This could be due to the sudden shunting up of land at or near a plate boundary, associated with an earthquake. The Kashmir earthquake of 2005 resulted in an area of land being uplifted by 10m. The land could also rise due to a rebound effect. This is currently happening in the UK, where north west Scotland, which was previously covered in ice for thousands of years, is now rebounding back at a rate of per year (The south east of England, which is obviously joined to it is sinking down as a result of this).

10. earthquakeKashmir rebound Scotlandice ice Polesmountains Lessfurther flood plainsIsostatic rising seaboundary erosive valley floorscut energy graded profileregradingmouth upstream knickpoint eustatic falling land glacials locked up gradientwaterfall rejuvenatedbase levellowered upliftlowerdowncuttinggravitational potential heightsea levelmeanders gorgesterraces Englandsinking

11. So, Rejuvenation… A river is said to be rejuvenated when the base level that it is flowing down to is lowered. This can happen by uplift of land, or by a sea or lake that it is flowing into becoming lower. That makes the river suddenly start eroding its bed vertically (downcutting) faster as it gains gravitational potential energy. This is due to the river suddenly having an increased height to fall downhill to reach sea level. This causes meanders cut down as gorges, stretches of river that are much faster and terraces cut down sharply into existing flood plains. The main causes of this process of rejuvenation are: Isostatic change –land rising relative to the sea. This could be due to the sudden shunting up of land at or near a plate boundary, associated with an earthquake. The Kashmir earthquake of 2005 resulted in an area of land being uplifted by 10m. The land could also rise due to a rebound effect. This is currently happening in the UK, where north west Scotland, which was previously covered in ice for thousands of years, is now rebounding back at a rate of per year (The south east of England, which is obviously joined to it is sinking down as a result of this).

12. Eustatic change – sea falling relative to the land. One of the most common ways for this to happen is during colder periods called glacials. Water is locked up as ice on the land (ice caps at the Poles, glaciers in the mountains). Less water is released back into the oceans, meaning that sea level falls. In both cases, water now has further to fall, meaning more erosive power. So existing flood plains and valley floors are cut into due to these new energy levels. The river is changing its graded profile, sometimes called regrading. This starts at the mouth of the river and then moves upstream, basically because the change took place at the mouth. The limit of the regrading is marked by a knickpoint. Upstream of this point the original graded profile is unaltered. Here there is likely to be a sudden change in gradient or even a waterfall.

13. So, Isostatic

14. So, Eustatic

15. Incised Meanders River Terraces

16. River Terraces River Terraces were created by the building up of river gravel beds. When the sea-level rose the river flow became slower, depositing sheets of gravel (1) then, during the glacial periods the sea-level fell and the river cut down into the gravel leaving a terrace on either side (2). As the sea-level lowered in each succesive phase throughout the Ice Age a series of terraces were formed, of which the highest is the earliest (3, 4, 5).

17. A Knickpoint Waterfall

18. Complete the table below using: • Waugh 74-76 • Nelson Thornes AQA AS Geography 22-23 • Barker, Redfern and Skinner AQA AS Geography • Own research and reading