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

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)

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

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