Chapter 3 - Denudation Flashcards
What is denudation?
Denudation is the breakdown and removal of solid and loose rocky materials.
What is weathering?
Weathering is the breakdown of rocks exposed on the earths surface. Unlike erosion, there is no transportation of the material involved
Name the 3 types of weathering
- Mechanical
- Chemical
- Biological
Explain mechanical weathering
Mechanical weathering occurs when rocks are broken into smaller pieces due to the action of sun and frost occurring in areas where there is no vegetation cover to protect the rock
Explain chemical weathering
Breaking down of rocks due to chemical changes within the rock
Explain biological weathering
Biological weathering occurs when tree roots or animals widen spaces within the rock or soil
What is erosion?
Erosion is the breakdown of rocks AND the transportation of this material
What causes erosion? Give examples
- Moving water, e.g. rivers and seas
- Moving ice, e.g. glaciers
- Moving air, e.g. wind
What is freeze-thaw action?
Form of mechanical weathering.
- Water gets into cracks in the rock
- Water freezes putting pressure on surrounding rock
- After some time, this continual temperature change puts pressure on the rock eventually causing it to crumble and break
Explain exfoliation
- Form of mechanical weathering
- Occurs in areas of extreme temperature change
- When the temperature rises very high and falls very low, the rock expands and contracts causing the outer layer to shatter
- Also known as ‘onion peeling’
What is carbonation?
- Rain falls and takes in carbon dioxide forming a weak carbonic acid.
- This rain then falls on limestone and reacts with the calcium carbonate in the limestone slowly dissolving it
Define ‘karst’
Term used to describe distinctive landforms that develop on rock types (usually limestone) which are easily dissolved by water
What is a limestone pavement?
An exposed area of limestone
What are ‘clints’ and ‘grikes’?
- Clints are the flat areas of rock on a limestone pavement
- Grikes are deep fissures or cracks in a limestone pavement
What is a swallow hole?
An enlarged grike is known as a swallow hole. Rivers and surface water dissapear through these swallow holes
E.g. Pollnagcolm in the Burren
How are caves made?
When rivers dissapear underground though a swallow hole, Limestone is dissolved and passages eventually form large caverns or caves
E.g. Aillwee Caves in the Burren
What are stalactites?
Drops of water containing calcium carbonate drip down from the roof of the cave, which in time drip to the floor. This leaves a tiny particle of calcite attached to the roof and over thousands of years these grow downwards forming columns of calcite
What are stalagmites?
Drops of calcite fall from the stalactites onto the floor and these drops then evaporate leaving a build-up of calcite.
What are pillars?
Pillars occur when a stalactite and a stalagmite grow together to form a pillar of calcite
What is mass movement and what is regolith?
Loose weathered material that moves down a slope under the influence of gravity. This material is known as regolith
Name 4 factors that affect mass movement
- Gradient
- Water content
- Human activity
- Plants and trees
Describe a soil creep
- Slowest type of mass movement (around 1cm per year)
- Greatest at surface, decreases with depth of soil
What evidence of soil creep do we see on the landscape
- Tilted telegraph poles
- Broken and tilted fences
- Soil piled up behind walls causing them to bulge and collapse
- Terracettes
- Tree trunks turned downslope
- Cracks in the road
Describe bog bursts
Occur in upland slopes when bogs become saturated causing the bog to flow down the hillslope causing devastation as it travels
Describe mudflows
Occurs when saturated regolith flows rapidly downslope
Describe landslides
Occur when a slope becomes unstable, resulting in a very rapid movement of regolith down a steep slope
Describe an avalanche
Occurs when the weight of snow is too much for the slope to hold
