Mass Movement Flashcards
What is mass movement?
Mass movement refers to loose weathered material (regolith) that moves downslope under the influence of gravity
What are the 4 factors if mass movement?
- Gradient/slope
- Deforestation
- Water content
- Construction of roads/rail (human activities)
Causes: What are human activities/interaction?
Construction of roads/rail which undercuts slopes, making them unstable and steeper leading to mass movement e.g. rock fall
Causes: What happens with steeper slopes (gradient)?
They increase the likelihood of mass movement
Causes: What is water content?
Seepage after heavy rainfall, can act as a lubricant making materials more likely to slide. Water also adds weight to the slope
Causes: What is vegetation cover?
Roots help bind soil together; and trees also absorb much of the water. Deforestation increases the risk of mass movement
Causes: What are earthquakes/volcanic activity?
Seismic activity or volcanoes can lead to landslides e.g. lahar
What is a landslide?
A landslide is the sudden movement of rock, soil and debris down a slope due to gravity
How do landslide happen?
It happens when the stability of the slope is weakened by factors such as heavy rainfall, deforestation, and/or human activities like construction of roads, rail or buildings
What do the factors of a landslide cause?
These factors reduce friction and support , causing the material to slide downhill
Where does soil creep occur?
Soil creep occurs as soil moves very slowly down gentle slopes
How fast does soil creep move?
Soil creep is the slowest form of mass movement. It moves at a speed of 1cm every year.
We only notice its effects on the landscape from the clues it leaves after many years
How can we tell that soil creep is happening?
*Tree trunks, fences and poles may lean/ bend in the direction of soil creep
*Soil sometimes accumulates in a series of small ridges called terracettes
*Soil piles up behind walls, causing them to bulge and break
Where is soil creep greatest?
At the surface
What are the small ridges of soil called
Terracettes
What is the name of the case study
The 2018 Southern California landslide
Where did the landslide occur
In Montecito
What were the causes of the landslide
The Thomas fire (in 2017) and heavy rainfall
What damage did the landslide destroy
It destroyed homes,roads and infrastructure
How many people did the landslide kill and injure
It killed 23 people, injured many others and caused massive property damage
