Mass Movements, Wind, and Glaciers Chapter 8

Mass Movements, Wind, and Glaciers Section 8.1: Mass Movements Section 8.2: Wind Section 8.3: Glaciers

Section 8.1:Mass Movements Objectives Analyze the relationship between gravity and mass movements. Identify factors that affect mass movements. Distinguish between types of mass movements Relate how mass movements affect people.

Over Riding Concept Mass movements alter Earth’s surface over time due to gravity moving sediment and rock down slope.

Mass Movements The down slope movement of soil and weathered rock resulting from the force of gravity is called mass movement. Because climate has a major effect on the weathering activities that occur in a particular area, climatic conditions determine the extent of mass movement.

Factors that Influence Mass Movements Several factors influence the mass movements of Earth’s Materials: Material Weight Resistance to sliding or flowing Triggers that shake material lose Water

Types of Mass Movements Creep The slow, steady, downhill flow of loose, weathered Earth materials, especially soils, is called creep. The effects of creep are usually noticeable only over long periods of time.

Types of Mass Movements Creep One way to tell whether creep has occurred is to observe the positions of structures and objects.

Types of Mass Movements Flows Earth flows are moderately slow movements of soils, whereas mudflows are swiftly moving mixtures of mud and water.

Types of Mass Movements Mudflows can be triggered by earthquakes or similar vibrations and are common in volcanic regions where the heat from a volcano melts snow on nearby slopes that have fine sediment and little vegetation. Mudflows are also common in sloped, semi-arid regions that experience intense, short-lived rainstorms.

Types of Mass Movements Slides A rapid, down slope movement of Earth materials that occurs when a relatively thin block of soil, rock, and debris separates from the underlying bedrock is called a landslide.

Types of Mass Movements Slides Landslides are 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 sliding surface. Rockslides are often triggered by earthquakes.

Types of Mass Movements When the mass of material in a landslide moves along a curved surface, a slump results. The material at the top moves slightly inward, while the material at the bottom moves outward.

Types of Mass Movements Rock falls On high cliffs, rocks that are loosened by physical weathering processes or by plant growth can break up and fall directly downward. Rock falls commonly occur at high elevations, in steep road cuts, and on rocky shorelines.

Mass Movements Affect People Human activities such as construction of buildings, roads, and other structures can make slopes unstable, contributing to the factors that cause mass movements.

Mass Movements Affect People Reducing the Risks The best way to reduce the number of disasters related to mass movements is to educate people about the problems of building on or near steep slopes.