Figure 11 Creep can be caused by the alternate freezing and thawing of water in soil. Slumping often occurs when soil that is rich in clay is soaked by water. Predicting How would the steepness of the slope of the hillside affect the amount of creep or slumping?
Mass Movement
Once weathering loosens particles of rock, the particles, or sediment, do not stay in the same place. Mass movement is the downward movement of rock and soil due to gravity. 
Through the process of mass movement, gravity moves loose material down a slope. There are several types of mass movement.
Landslides
The rapid movement of large amounts of rock and soil is a landslide. Landslides often occur after heavy rains or after earthquakes loosen materials on a steep slope. Landslides that occur on the sides of mountains can destroy entire towns.
Mudflows
Rapid mass movements of soil and other sediment mixed with water are called mudflows. Mudflows tend to occur in areas where fine sediment has collected in thick layers. When it rains, water loosens the sediment and increases its weight. After a heavy rainfall, the sediment mixed with water washes down the slope.
Creep
Creep occurs when soil gradually moves down a slope. Creep often occurs because of the formation of ice. Each time the ground freezes, the soil expands outward. When the ground thaws, the soil moves a small distance downhill. Creep, shown in Figure 11, happens so slowly that it's hard to notice. But over time the results of creep become evident.
Slumping
Slumping occurs when weak layers of soil or rock suddenly move downslope as a single unit. Gravity acting on water-saturated soil and rock causes slumping. Slumping often leaves a curved scar.
Section 23.2 Assessment
Reviewing Concepts
- What is erosion? List five agents of erosion.
- How are mechanical weathering and chemical weathering similar? How do they differ?
- What three factors are most significant in determining the rate at which rocks weather?
- How does gravity cause erosion?
Identify three processes that cause mechanical weathering.
What is the role of rainwater in chemical weathering?
Critical Thinking
Predicting Would you expect chemical weathering to occur more rapidly in a desert or in a rainforest? Explain.
Relating Cause and Effect What conditions can cause landslides and mudflows?
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