1. Isostasy Cycle of movement of Earth’s crust: Chapter 14: Isostasy
The upper section of Earth’s crust eroded
Continental crust rises upwards
Glacial ice pushes continental crust downwards
Glacial ice melts, landmasses rise upwards

2. When land is uplifted, a change in a river’s base level occurs
Chapter 14: Isostasy
When land is uplifted, a change in a river’s base level occurs
Ability to erode is reborn
Rejuvenation occurs

3. Eustatic movement Changes in the amount of water in oceans
Chapter 14: Isostasy
Eustatic movement
Changes in the amount of water in oceans
Linked to global climatic change
Earth’s climate cools water stored in glaciers
Reduction in sea level
Ice age ends
Rise in sea level

4. Exogenetic forces Processes which occur at or near the Earth’s surface
Chapter 14: Isostasy
Exogenetic forces
Processes which occur at or near the Earth’s surface
E.g. erosion as a result of wind, water, ice and activities of animals and humans

5. Endogenetic forces Processes operating below the Earth’s crust
Chapter 14: Isostasy
Endogenetic forces
Processes operating below the Earth’s crust
Form surface features such as folds, faults and volcanoes

6. Isostatic equilibrium
Chapter 14: Isostasy
Isostatic equilibrium
Balances of forces due to varying weights of landmasses in close proximity to each other

7. Chapter 14: Isostasy
Base level
Generally equal to sea level

8. Features of adjustment to base level
Chapter 14: Isostasy
Features of adjustment to base level
1. Knickpoints
Sudden change in the slope of the long profile of a river
Evidence of rejuvenation
‘Rebirth’ of erosive power that is only found usually in the youthful stage of a river
Usually marked by waterfalls or rapids
e.g. Kathleen’s Falls, River Erne, Ballyshannon, Donegal

9. Features of adjustment to base level
Chapter 14: Isostasy
Features of adjustment to base level
2. Incised meanders
Incised means ‘cut deeply’
Caused by vertical erosion
River erodes down into its floodplain
Creates incised meanders
e.g. River Nore at St Mullins in Co. Carlow

10. Features of adjustment to base level
Chapter 14: Isostasy
Features of adjustment to base level
3. Terraces
Rejuvenated river
Vertical erosion in old stage
River has a wide floodplain
Waterfalls form
River erodes in the old stage
New floodplain forms by lateral erosion
Old floodplain appears like a step above the new floodplain
Steps also known as terraces
On both sides of a river, called paired terraces
e.g. along the River Barrow, Co. Kilkenny

11. Features of adjustment to base level
Chapter 14: Isostasy
Features of adjustment to base level
4. Raised beaches
Common in glaciated regions
Glaciation ends, level of the land surface readjusts
Former beach left located above the coastline/shoreline of current sea level
e.g. Donegal Bay

12. Development of a landscape
Chapter 14: Isostasy
Development of a landscape
Three stages:
Early
Middle
Late

13. Development of a landscape
Chapter 14: Isostasy
Development of a landscape
1. Early stage
Topography flat
Narrow streams and rivers

14. Development of a landscape
Chapter 14: Isostasy
Development of a landscape
2. Middle stage
Vertical erosion
Valleys carved out

15. Development of a landscape
Chapter 14: Isostasy
Development of a landscape
3. Late stage
Lateral erosion
Floodplains
Peneplain – rare occurrence

16. Peneplains Low relief plain close to a river Flat surface
Chapter 14: Isostasy
Peneplains
Low relief plain close to a river
Flat surface
Lies at an elevation close to sea level
Result of long-term erosion
e.g Munster Peneplain