Process and impact of rejuvenation

Question 1

Rejuvenation meaning

Answer 1

to restore to a former state; to make fresh or new again

Question 2

Dynamic equilibrium

Answer 2

where there is a balance between the rate of erosion and deposition

Question 3

Dynamic rivers

Answer 3

Rarely ever, if ever, in state of dynamic equilibrium

changes in discharge and sediment load are constantly changing the profile of the river.

Question 4

Base Level Changes

Answer 4

Eustatic change- changes to sea level

Isostatic change: Glacial rebound

Question 5

Eustatic (global) change

Answer 5

Decrease in global temperatures causes more snow (precipitation), becomes ice so more water on stored on land.

Rise in temperatures melts ice and glaciers causing rise in sea level

Question 6

Isostatic (local) change

Answer 6

RISE- glacial period, glaciers cause crust to sink lower into mantle

FALL- end of glacial period, ice melts, crust slowly rises, sea level falls

Question 7

Causes of Rejuvenation

Answer 7

Tectonic Changes

Fall in Sea levels due to eustatic + isostatic changes

River capture

Question 8

How does a river become rejuvenated?

Answer 8

• Renewed period of vertical erosion to achieve a newer and lower base level
• Fall in base level means river now has more energy to actively erode the irregularity.
• Over time river can achieve a state of equilibrium with a long, smooth profile.

Question 9

How is a knick point formed?

Answer 9

Through a fall in base level

Retreats upstream over time like a waterfall

Question 10

What happens when a river is rejuvenated?

Answer 10

~Adjustment to new base level starts at sea and works way upstream gradually.

River gains more cutting power (vertical), adjusts long profile

Question 11

Effects of Rejuvenation

Answer 11

Renews river capacity to erode (increase in potential E)

Landforms as moves upstream:

• Knickpoint
• Waterfalls
• Rapids
• River Terraces
• Incised Meanders

Question 12

What is a knick point?

Answer 12

a sudden break or irregularity in the gradient along the long profile of a river

Question 13

What is a river terrace?

Answer 13

a remnant of former flood plain which has been left at a higher level after rejuvenation of river

Question 14

Benefits of River Terraces

Answer 14

Provide useful shelter from floods in a lower course river valley and natural route ways for roads and railways.

Question 15

How are river terraces formed?

Answer 15

• Lateral erosion
• Meander migration
• valley widened
• Deposition of sand and silt during floods

Question 16

why do incised meander occur?

Answer 16

if a rejuvenated river occupies a valley with well-developed meanders, renewed energy results in them becoming incised or deepened.