1. 11: Erosion Weathering – disintegration and decomposition
of material at or near the surface
Mechanical weathering
Breaking of rocks into smaller pieces
Frost wedging
Unloading
Biological activity
Ex. Plant roots, burrowing animals
Ex. Human activity
Chemical weathering
Alters the internal structures of minerals.
Minerals altered by removing or adding elements.
Most important agent is water.
Oxygen dissolved in water oxidizes
Carbon dioxide (CO2) in water forms
carbonic acid (H2CO3); alters material
Erosion – the incorporation and transportation
of material by a mobile agent, usually water,
wind, or ice.
Figure 4.4: Frost wedging
Figure 4.5B: Igneous mass fracture

2. Mass Wasting Def: The downslope movement of rock, regolith
and soil under the direct influence of gravity
Gravity is the controlling force.
Important triggering factors:
Saturation of the material with water .
Destroys particle cohesion
Water adds weight
Over-steepening of slopes.
Unconsolidated granular particles assume stable
slope called the angle of repose .
Stable slope angle different for various materials.
Over-steepened slopes are unstable.
Removal of anchoring vegetation.
Ground vibrations from earthquakes.
Google Images: Landslide
(Massive Landside, 3:21)

3. Processes Mud, earth, rock, debris, etc. The movement of the material:
Fall (free-fall of pieces)
Slide (material moves along a well-defined surface)
Flow (material moves as a viscous fluid)
Rate of movement: slow or fast
Google Images: Mass Wasting

4. Types Process types defined by rate of movement, fast or slow.
Creep: slow movement of soil and regolith downhill
Causes fences and utility poles to tilt.
Slump: rapid movement along a curved surface.
Occur along over-steepened slopes.
Rockslide: bedrock moves rapidly downslope.
Debris flow: rapid flow of debris with water.
Often confined to channels.
Problems in dry areas with heavy rains.
Lahars: volcanic material debris flow.
Earthflow: rapid, hillsides in humid regions.
Google Images: Mass Wasting