1. Denudation: Weathering and erosion
Chapter 6
Denudation: Weathering and erosion

2. Learning outcomes In this chapter you will learn:
How the surface of the Earth is shaped by denudation
That both weathering and erosion are known as denudation
About landforms that are created by these processes
How humans can interfere with these processes

3. Can you give examples of weathering?
Denudation
Rocks and soil worn down by processes
Collectively known as denudation
Two main processes: weathering and erosion
Weathering – breakdown of exposed rock, material remains
Erosion – breakdown of rock and removal of particles
Can you give examples of weathering?
Exam hint: You may be asked to explain what weathering and erosion are.

4. Weathering and erosion
Mechanical weathering:
rocks broken into smaller pieces
freeze-thaw action
Chemical weathering:
rocks dissolved
chemical reaction
carbonation
Moving water (Ch11)
Moving ice (Ch13)
Moving wind (Ch19)
Exam hint: You need to be able to give examples of mechanical and chemical weathering.

5. Mechanical weathering: Freeze-thaw action
Occurs high in mountains
Lots of precipitation (rain, sleet, snow)
Temperature drops below freezing
(1) During day, water seeps into cracks in rocks
(2) At night, temperature drops, water freezes and expands
(3) Process continues and weakens rock – pieces of rock break off and gather as scree at base of slope
Exam hint: You need to be able to describe how freeze-thaw action weathers rocks.

6. Chemical weathering: Carbonation
Rain takes in carbon dioxide from atmosphere
Rainwater mixes with carbon dioxide
Forms a weak carbonic acid
Carbonic acid effects limestone
Limestone contains 80% calcium carbonate
Weak carbonic acid reacts with calcium carbonate in limestone and dissolves it
Permeable rock – so rainwater passes down through rock
Exam hint: You need to be able to describe how carbonation weathers rocks.

7. Karst landscape
Karst landscape – area of bare limestone rock, exposed to weather
The Burren, Co. Clare – soil removed by glaciation
Unique landscape – surface and underground features
Exam hint: You may be asked to explain what a karst landscape is and give an example.

8. Karst landscape: Surface features
Limestone pavement
Swallow hole
Rainwater passes through vertical joints
Carbonation of surface and joints
Joints become wider
Creates grooves – grikes
Block in between – clints
Known as limestone pavement
River reaches limestone surface
Carbonation widens joints and bedding planes
River disappears underground through swallow hole
Vary in size
Pollnagollum – 6 metres wide, 16 metres deep
Exam hint: You need to be able to describe surface features and how they were formed.

9. Karst landscape: Underground features
Caves and caverns
Stalactites, stalagmites and pillars
Rivers flow underground
Carbonation enlarges passages
Form caves
Can be further enlarged
Form large chambers – caverns
Ailwee Caves, the Burren
Water seeps through rock
Carries dissolved limestone
Water reaches roof of cave or cavern
Drops evaporate, leave behind deposits of calcite
Build up, form stalactites (from roof)
Drops may fall on ground
Evaporate and leave calcite
Build up, form stalagmites (from floor)
Stalactite and stalagmite may meet – form pillar/curtain
Exam hint: You need to be able to describe underground features and how they were formed.

10. Karst landscape: Underground features
Explain how these underground features are formed.

11. The Burren – A karst landscape
Unique landscape
Region of exposed limestone
Limestone formed 300 million years ago
Chemical weathering
Major tourist attraction
Visited by botanists, adventurers, geologists
Creates employment
Exam hint: You need to be able to describe the Burren and explain why tourists are attracted to it.

12. The Burren – Tourism Advantages Disadvantages Provides employment
Reduces migration
Brings income – better services and infrastructure
Creates spin-off businesses
Increases pollution
Conflict over visitor centre
New buildings can destroy scenery
Walkers damage flora and fauna
Exam hint: You may be asked about the advantages and disadvantages of tourism in the Burren.

13. Sample answer
Explain three reasons why tourists might like to visit the Burren in Co. Clare.
Answer: The Burren is a unique karst landscape with many surface and underground features. It attracts botanists who come to see the unusual plant life. Geologists are interested in the rock features. Adventurers come to explore the caves and caverns.
(ii) Describe one advantage and one disadvantage of tourism in the area.
Answer: One advantage of tourism in the area is that it creates employment. One disadvantage is that increased pollution can damage the limestone.