Section 8.1 Flashcards
What is mass movement?
The downslope movements of loose sediments and weathered rock resulting from the force of gravity.
What are the four variables that influence mass movements?
1) Materials weight- resulting from gravity which works to pull the material down a slope.
2) Materials resistance to sliding or flowing
3) A trigger, such as an earthquake that works to shake material loose from a slope
4) Water
What is creep? When are the effects noticeable? Examples?
The slow, steady downhill flow of loose weathered materials, especially soils. The effects are usually noticeable only over long periods of time. Examples are: tilting of once vertical utility poles, fences, gravestones, the bending of trees. Loose materials on almost all slopes undergo creep.
What are flows? What is the difference between earth flows and mud flows? How are mudflows triggered and where are they common?
In some mass movements, Earth materials flow as if they were a thick liquid. Materials can move slowly or rapidly. Earth flows are slow movements of soils whereas mudflows are fast movements of mud and water. Mudflows can be triggered by Earthquakes and are common in volcanic regions as well as in regions that are sloped, semi-arid and that experience intense, short-lived rainstorms.
What are slides? Where is a landslide common? What is a rock slide?
A rapid, downslope movement of Earth materials that occurs when a relatively thin block of loose soil, rock, and debris separates from the underlying bedrock is called a landslide. The material rapidly slides downslope as one block, with little internal mixing. A landslide is common on steep slopes, especially when soils and weathered bedrock are fully saturated by water. A rock slide is a type of landslide that occurs when a sheet of rock moves downhill on a living surface. Relatively thin blocks of rock are broken into smaller blocks.
What are falls? Where are they common? Less common?
Commonly occur at high elevations in steep road cuts, and on rocky shorelines. Rocks are loosened by physical weathering processes. As they break up and fall downward, they may produce talus (cone-shaped pile of debris). On human made rock walls, falls are particularily common. Less common in humid areas with lots of vegetation.
What human activities contribute to the factors that may cause mass movement?
Activities such as constructing heavy buildings, roads, and other structures which make slope materials unstable. Also, poor maintenance of septic systems, which often leads, can trigger slides.
How can humans prevent mass-movement disasters?
Avoiding building structures on steep and unstable slopes, trenches can be dug to divert running water around a slope to control drainage. Other approaches to avoid landslides include covering steep slopes with materials such as steel nets and constructing protective fences along highways as well as the installation of retaining walls. The best approach though, is educating people about the problems of building on steep slopes.
