Chapter 13: Weathering, Karst Landscapes, and Mass Movements

Geography 1111 Chapter 13: Weathering, Karst Landscapes, and Mass Movements The term regolith refers to the upper layers of the surface that are exposed to weathering. Sediments are the unconsolidated, fragmented products of weathering processes from which soils develop. Joints and fractures in rock are important to weathering because they increase the surface area on which air, water, dissolved acids, and salts can operate. Generally speaking, root wedging is less influential than frost action among mechanical weathering processes. Frost action is particularly important in high mountain environments, where it produces rock fragments that accumulate as talus slopes at the base of cliffs. Collapsed sinkholes are circular depressions that form in karst landscapes when solution sinkholes collapse into subterranean caverns. Mass movements occur on slopes under the influence of gravitational stress. Any process that wears away or rearranges landforms is called denudation . Crystallization (salt-crystal growth) is an especially important physical weathering process in arid environments. Pressure- release jointing often creates exfoliation domes . The Madison River Landslide in Mo ntana was triggered by an earthquake . Karst topography refers to distinctly pitted and weathered limestone landscapes. Variations in the resistance properties of rocks is the cause of differential weathering. Joints are separations or fractures in rock that occurs without displacement of the sides. (Without faulting) The angle of repose represents a balance of driving forces and resisting forces on a slope. When the moisture content of moving material is high, it is called a flow. The point at which there is enough energy to overcome resistance against movement in a geomorphic system is called a threshold. Time of day would not likely be a contributing factor in a mass movement event. Physical weathering process involving water absorption, expansion, and the forcing of rock grains apart: hydration. Chemical weathering process involving the dissolution of minerals; commonly found in limestone: carbonation. A type of mass movement induced by human activities: scarification. Physical weathering process involving the mechanical work of crystal formation on rock:crystallization. Chemical weathering process exemplified by the formation of rust on rocks or soil: oxidation. Any unit movement of a body of material with gravity: mass movement.  Persistent, gradual mass movement of surface soil: soil creep.   Sudden rapid movement of a cohesive mass of unsaturated regolith or bedrock: landslide. The general process involving mass movement and erosion of the landscape: mass wasting. Mass of falling rock, debris, and soil:debris avalance. Downhill movement of material with a high moisture content:mudflow.