Weathering and Mass Movement Flashcards
What is weathering?
Weathering is a process by which the specific surface area of a rock is increased.
What is the effect of weathering on quartz?
Quartz is very resistant to all types of weathering, whereas other rocks just decay into clays.
What are the different types of physical weathering?
- Mechanical unloading
- Mechanical loading
- Freezing
- Wetting and drying
- Crystallisation
How does mechanical unloading cause weathering?
Allows fissures to open up causing materials to expand vertically, resulting in horizontal cracks appearing in the bedding plane.
How does mechanical loading cause weathering?
Impact by rain, sand and dust in the air, or sand, gravel and boulders in the water results in material breaking away from the surface of a rock.
How does freezing cause weathering?
When water freezes, it expands applying pressure on cracks causing them to open up and disintegrate the rock.
How does wetting and drying cause weathering?
Wetting and drying causes materials to expand and contract giving a similar effect to that of freezing, just not as powerful.
How does crystallisation cause weathering?
Crystallisation has a similar effect to that of freezing.
What are the different types of chemical weathering?
- Solution
- Carbonation
- Oxidation
- Hydrolysis
How does solution cause weathering?
This is when rock is dissolved in water (especially with salt).
How does carbonation cause weathering?
Slightly acidic rainwater containing dissolved carbon dioxide leads to the solution of a rock.
How does oxidation cause weathering?
- Rock reacts with oxygen causing them to break down.
- This causes clay to turn from blue/grey to brown/red.
How does hydrolysis cause weathering?
Hydrolysis is an irreversible reaction with water, causing one rock to decompose into another.
What is the difference between chemical and physical weathering?
- Chemical weathering processes generally happen quicker and at higher temperatures.
- However, all weathering processes are helped by high rainfall.
Which factors affect mass movement?
- Nature of material
- Water content
- Slope steepness
How does water content affect mass movement?
- A little water allows a slope to stand very steeply as the water forces are significantly larger than the weight of the grains.
- If the slope dries out or becomes saturated, the water forces disappear as there is no longer any tension between the water and the air, and so the slop cannot stand as steeply.
What factors affect landslides?
- The more brittle the material, the faster it moves.
- If high pressure water/air is mixed in, then movement can be very fast.
What are the features of a rockslide?
When everything comes to a halt, the material breaks up and so can often turn into a flow.
What is a rock avalanche?
An avalanche of rocks which is triggered by an earthquake.
What feature is left behind after slumping?
A scar.
What is soil creep?
- When surface layers of the ground expand they move directly outwards.
- They then contract, moving vertically downward, causing particles to move in a zig-zag motion down hill.
- The expansion and contraction can be caused by changes in moisture content or freezing and thawing.
