Slumps often happen when a slope is undercut, with no support for the overlying materials, or when too much weight is added to an unstable slope. The white areas on green hillsides mark scars from numerous mudflows.
In this section, you will learn the term mass wasting.
Falls are abrupt movements of masses of geologic materials, such as rocks and boulders, that become detached from steep slopes or cliffs. Use this quiz to check your understanding and decide whether to 1 study the previous section further or 2 move on to the next section.
Movement is caused by shear stress sufficient to produce permanent deformation, but too small to produce shear failure.
On hillsides with soils rich in clay, little rain, and not much vegetation to hold the soil in place, a time of high precipitation will create a mudflow. If a landslide flows into a lake or bay, they can trigger a tsunami figure 4.
Geologists are studying the warning signs and progress of local landslides to help reduce risks and give people adequate warnings of these looming threats. Landslides are exceptionally destructive. Landslides often occur on steep slopes in dry or semi-arid climates.
The lahar caused by the eruption of Nevado del Ruiz in Columbia in 1985 killed more than 23,000 people. Curves in tree trunks indicate creep because the base of the tree is moving downslope while the top is trying to grow straight up figure 8.
Rocks that fall to the base of a cliff make a talus slope figure 1. Tilted telephone or power company poles are also signs of creep. You will also be exposed to the various types of mass wasting, their causes and their effects.
Landslides and avalanches are the most dramatic, sudden, and dangerous examples of earth materials moved by gravity. Landslides may create lakes when the rocky material dams a stream. There are generally three types of creep:.
Answer the question s below to see how well you understand the topics covered in the previous section. Search for: Figure 7.Massive Rock Fall