Geology of Urban Watersheds - Urban Watersheds: Geology, Contamination, and Sustainable Development - page 32

Scarps

Rock fall

Slump

Chute

Talus

Fissure

Debris
flow

Deranged
forest

Scarp
Backward
rotated
surface

Toe

Ponded
water

Slump
blocks

Glide plane Transverse

ridge

FIGURE 2.9
Examples of mass wasting. (From United States Geological Survey, USGS glossary, http://3dparks.wr.usgs.gov/
haywardfault/images/slump.jpg, (accessed June 28, 2010), 2010b.)

Main scarp

Crown

Grass

Slump block

Toe

Earth flow

FIGURE 2.10
Example of slumping. (Reprinted from Bloom, A.L., Geomorphology: A Systematic Analysis of Late Cenozoic
Landforms , 3rd edn., Waveland Press, Long Grove, IL, 2004. With permission.)

• Slump—The downward slipping of a coherent body of rock, regolith, or soil along
a curved surface or rupture. The original surface of the slumped mass and any
flat-lying planes within it become rotated as the mass slides downward. Figures
2.9 and 2.10 show a more detailed example of slumping.
• Debris flow—The rapid downslope plastic flow of a mass of regolith, soil, or debris.
Commonly forms as an apron-like or tongue-like area at its terminus with a very
irregular surface (Figure 2.9).
• Mudflow—The rapid downslope movement of a very plastic and almost fluid
mass of regolith, soil, or debris. Very similar to a debris flow but with a higher
water content (Figure 2.9).