Shaping the Earth’s Crust

1. Shaping the Earth’s Crust Weathering and Erosion

2. Shaping the Earth’s Crust • The rocks and soil of the earth’s crust are continually being worn down because of a number of processes. • These processes are known collectively as Denudation. • Denudation occurs as a result of both weathering and erosion.

3. Denudation • Denudation is caused by both weathering and erosion. Denudation WeatheringErosion • Mechanical Weathering 1. Moving water (rivers/sea) • Chemical Weathering 2. Moving Ice (glaciers) 3. Moving Air (wind).

4. Weathering and Erosion Weathering • Weathering means the breakdown of rocks that are exposed to the weather. • There are two types of weathering, Mechanical Weathering and Chemical Weathering Erosion • Erosion means the breakdown of rocks and the removal of their particles. • Erosion is caused by moving air (wind), moving water (rivers/sea), and moving ice (glaciers).

5. Mechanical Weathering • Mechanical weathering breaks up the rocks into smaller pieces. • One type of mechanical weathering is called Freeze-thaw action. • Freeze-thaw action breaks the rock into smaller pieces. • It occurs high in the mountains where there is lots of rain and the temperature rises above and below 0 degrees Celsius quite often.

6. Freeze-Thaw Action

7. Chemical Weathering • Chemical weathering dissolves rocks. • One example of chemical weathering is called Carbonation. • Carbonation occurs in limestone landscapes, where bare limestone rock is exposed to the rain. • It occurs because rainwater mixes with carbon dioxide in the atmosphere, forming a weak carbonic acid. • This acid reacts with calcium carbonate in the limestone, causing the rock to slowly dissolve.

8. Carbonation – Karst Landscapes • Carbonation occurs in areas where bare limestone rock is exposed to the weather. • These areas are known as karst landscapes, after a limestone region called Karst in Slovenia. • An example of a Karst landscape in Ireland is the Burren in Co. Clare. • Here the soil has been worn away, leaving the bare limestone rock exposed. Carbonation has created many spectacular features, particularly underground.

9. A Karst Limestone Pavement

13. Mass Movement • Mass movement means the movement of any loose material (rocks, soil, mud) down slope under the influence of gravity. • The loose material is known as regolith. • The rate of mass movement is influenced by 4 factors. • Gradient • Water Content • Human Activity • Vegetation

14. Influences on Mass Movement • Gradient – Mass movement occurs on sloping land. Mass movement is fastest on steep slopes. • Water Content – After heavy rain the regolith (loose material) is heavier. • Human Activity – People often cut into hillsides to make roads or railway lines. This creates steep slopes where mass movement can occur. • Vegetation – The roots of trees and plants help keep the regolith together, slowing down mass movement.

15. Types of Mass Movement • There are different types of mass movement. They are grouped according to the speed at which they occur. Types of Mass Movement Speed – Slow Speed – Fast 1. Soil Creep 1. Landslides 2. Bog bursts 3. Mudflows

16. Soil Creep

17. Soil Creep

18. Landslides

19. Mudflows