10. Mass Movement Flashcards
What is mass movement?
The downslope movement of regolith (weathered rock) under the influence of gravity
What are factors affecting mass movement?
- Slope/gradient
- water
- vegetation cover
- human activity
- tectonic activity
What is soil creep?
The slowest type of mass movement. Generally 0.5 cm per year, impossible to measure over short period
What are landslides?
Sudden and very fast movements of soil and rock. May be caused my excavation, sea erosion, earthquakes or heavy rainfall
How fast can landslides move?
Up to 300 km/hr
What are slumps?
Downward rotation of regolith occurs along curved surface. The upper surface and individual blocks remain relatively undisturbed
What are earth flows?
The relatively fast movement of wet soil on medium slopes. Can block roads and railways but do not threaten lives
What are bog flows?
The downslope movement of saturated peat
What are mudflows?
Faster and wetter than earth flows. Lahar’s are mudflows that result from volcanic activity e.g Nevado del Ruiz, Colombia
What are rockfalls?
Sudden movement of bare rock down cliffs or extremely steep slopes
What are avalanches?
Sudden, very fast movements of snow and ice down a steep slope, usually carrying regolith like stones and boulders
What is solifluction?
Slow, wet type of mass movement. Usually occurs in starred gentle slopes. Common after the last Ice Age
What is permafrost?
Means the ground is always frozen a metre below the surface. Permafrost prevents water from seeping through soil, causing it to be waterlogged
