R - Rejuvination Flashcards
What is rejuvenation?
It happens when sea level changes - it is the idea of the river trying to get back to a graded profile
- As the land/sea rises or falls - the river will change
What are the causes of rejuvenation? Why?
Tectonics and climate change
T - when land is uplifted after plate movement or volcanic activity
CC - Glaciation and changes in rainfall
What are the two types of sea level change?
Eustatic and Isostatic
What is Eustatic sea level change?
Global change in sea level - directly linked to the temperature of the Earth
- In warmer periods there’s less ice and the water is warmer so it expands an sea level rises
- In colder periods the ocean water is colder so contracts and sea levels fall
What is Isostatic sea level change?
Local changes where the height of the land changes relative to the global sea level
Eg glaciation - during glaciation the weight of the ice pushing down on the land to fall relative to the level of the sea - when the ice goes in warmer periods the land rebounds upwards
What are the features of rejuvenation
Knick point waterfalls, incised meanders, river terrances
What is a Knick point waterfall? And the formation?
These occur as an attempt to regrade the long profile to a normal concave shape
- There is headword erosion as the river cuts down into the land at the mouth
This process slowly cuts the profile down to sea and base level from the mouth and then consequently upstream
What is a River Terrance? How is it formed?
This is where vertical erosion occurs in a flooplain that was previously being formed by the normal conditions of deposition ad lateral erosion
-The river cuts downwards abandons the old flood plain as a river Terrance
What is an Incised Meander? How is it formed?
One which lies at the bottom of a steep-walled canyon
-When the river keeps its meandering course as vertical erosion increases - the result is a deep, winding valley with steep sides
The river is left far below the level of the former flood plain
What s the difference between an entrenched and an ingrown meander?
Entrecnhed: Symmetrical cross section and occur if valley sides are resistant to erosion
Ingrown; Less rapid uplift of land, allowing river to shift laterally across the floodplain
