Lesson Summary
- Gravity moves earth materials from higher elevations to lower elevations.
- Landslides, avalanches and mudflows are very rapid and dangerous examples of erosion
by gravity. - Slump and creep happen slowly but surely, moving material downslope.
- Planting trees and vegetation, building retaining walls and providing good drainage
are ways to help prevent this type of erosion.
Review Questions
- Name three ways that gravity moves materials. Describe each.
- What natural events and human actions can trigger a landslide or avalanche?
- What makes landslides and avalanches move at such great speeds?
- Compare and contrast a mudflow and a lahar.
- Name two ways that soil can move slowly down a slope.
- What can people do to help prevent landslides or mudflows?
Vocabulary
avalanche Mass of snow that suddenly moves down a mountain under the influence of
gravity.
creep Exceptionally slow movement of soil down hill.
lahar Volcanic mudflow formed when heavy rains or snow and ice melt and combine with
volcanic ash & dust.
landslide Rapid movement downslope of rock and debris under the influence of gravity.
mudflow Saturated soil that can flow very rapidly or slowly down a slope depending on
the viscosity of the flow.
saturated Soil that has become completely soaked with water.
slump Downslope slipping of a mass of soil or rock, generally along a curved surface.
talus slope A pile of angular rock fragments formed at the base of a cliff or mountain.