Rocks and weathering 3.3 Flashcards
1
Q
What is mass movement?
A
The downslope movement of rock and weathered debris by gravity alone.
2
Q
What are the 4 main types of mass movement?
A
- Creep
- Flows
- Slides
- Falls
3
Q
Types of MM: creep
A
- Slow, downslope movement of unconsolidated material and soft rock (1-2cm per year).
- As a result of plastic flow and heave.
- Waterlogged conditions can lead to accelerated creep known as solifluction.
- Leads to small ridges across hillsides known as terracettes.
4
Q
Types of MM: flows
A
- The rapid movement of rock and weathered debris mixed with water down valleys.
- Linked to steep slopes, narrow valleys, removal of vegetation and heavy rainfall.
- May be found on slopes of active volcanos where they are termed lahars.
5
Q
Types of MM: slides
A
- Single, dramatic events when a section of a hillside becomes unstable, shears away and moves downhill.
- Factors leading to slides include steep slopes, bedding planes, clay slopes,
saturation, vibrations and loading/removal on the slope.
6
Q
Case Study: The Vaiont Dam disaster
A
- A dam was constructed across the Vaiont river to produce hydroelectric energy.
- Heavy rainfall resulted in 270 million cubic metres of rock sliding into the reservoir as 25m/s.
- Created a wave of 100m high which flowed over the dam and into the valley below.
- Killed 2600.
7
Q
Types of MM: falls
A
- Share many features of slides.
- Produce scree at the base and rarely exceed 40 degrees.
- Angle of scree slope depends on size and shape of rock fragments and height of cliff.
8
Q
What is sheet wash?
A
Detachment of soil particles by raindrop impact and their removal downslope by water flowing overland as a sheet instead of in definite channels or rills.
9
Q
What are rills?
A
Rills are shallow channels which are cut into the soil by flowing water, which results in a form of soil erosion known as rill erosion.
