GEOG 1114 1st Edition Lecture 24Outline of Last Lecture -Vulcanism- Volcanic peaks-Volcanic DistributionOutline of Current Lecture -Weathering-Weathering processes-Biological Weathering-Mass wastingCurrent Lecture External Processes:WeatheringThe Mechanical disintegration and/or chemical decomposition that breaks down rock masses into progressively smaller pieces. Most are atmosphericOxygen, carbon dioxide, and water most importantTemperature changesWater penetration in bedrock openingsBiotic agents: Burrowing and/or plant roots, Chemical alterationThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.Facilitated by:Jointing: A fracture in a rock separating it Faulting: A break in a rock where the rock moves past each otherPore Spaces: The spaces in a rock that are unoccupied by materialProcesses of:Physical or Mechanical Weathering: The breakup of rocks by physical processes such as crustal movement and frost shattering.Frost Shattering: Water expands when it freezes. When water enters natural cracks in rock and freezes it breaks apart that rock. Chemical Weathering: Decomposition of rock material through chemical alteration of mineralsProcesses involving water and assisted by root activityChemical reactions cause rock disintegration by swelling and softeningThree General Types1. Oxidation: chemical reactions involving oxygen. Examples: orange rust that forms on iron and the green coating that appears on copper. Most soils and decayed rocks are shades of brown, due to the oxidation of iron-bearing minerals2. Hydrolysis: chemical union of water with another substance to produce a new component that is softer and weaker. Igneous rocks in particular. Silicate material combined with water causes expansion and contributes to mechanical disintegration3. Carbonation: reaction between carbon dioxide in water and carbonate rocks to produce calcium bicarbonate which is a vary soluble product. It is either carried away in run-off or it can be deposited in crystalline form if the water is evaporated. Biological WeatheringRoot Activity -- penetration of growing plant roots into cracks and crevices, which opens cracks further and contributes to mechanical weathering. Lichens -- algae and fungi living as a single unit on bare rock soil or bark. They draw mineral from the rock by ion exchange which weakens the rock. Expansion and contraction of lichens during wet and dry period flake off tiny particles of the rock.Burrowing Animal -- mixes soils and can be a factor in rock disintegration.Exfoliation :A physical and chemical weathering process in which curved layers of bedrock peel off in sheetsOccurs when curved and concentric joints develop in bedrock weakening rock letting water in Often lichen and frost shattering contribute to exfoliationLayer are removed; expansion of rocks occursCommon in granitesExfoliation domeMass Wasting: The process whereby weathered material is moved downslope under the direct influence of gravity.Factors that influence mass wasting: Angle of repose, Impact of water on lubrication of rock material, Clay-water mixture is a very slick and mobile substanceRates are related to slope angle, material forming the slope, and moisture content of the slope material.Rock fall: Talus/ Scree-Uniform accumulation of rock fall material; talus apron-Material tends to collect in the cone shaped heapsLand Slide: Instantaneous mass slope collapse with no fluid flow lubrication-Initiated from added weight from rainfall or earthquakes-Rock avalanches -Lost material leaves land scar-Damming of valley streams-Rotation of sliding material: slumpCreep: -Unobtrusive downslope flow of soil and regolith-Freeze/thaw and wet/dry effects on creep-Burrowing animals and plant root effects-Principle variables are slope angle, vegetative cover, and moisture supply Slump-Slope collapse -Concave in nature Mudflow-Wasting initiated or enhance by addition of water-Water primary force; clay can enhance motion as well-Earthflows: water saturated land moved downhill-Mudflows: originate in arid basins; muddy downslope flow that can accumulate large rock materialsRock Glaciers -Not all glaciers are made of ice -Some glaciers are made of rock-Need a climate cold enough to sustain permafrost-Compared to ordinary glaciers, rock glaciers are rare, and may look like a rocky field shaped like a glacier-While regular glaciers flow, rock glaciers creep Erosion: The removal of weathered material to another location.Primary Agents: Water (Fluvial Processes) Wind (Aeolian Processes)Fluvial Processes: Overall flow of water eroding, transporting, and depositing materialAeolian Processes: Erosion, transport and deposition of material by windBoth produce a variety of landscapes: Streams, rivers, lakes, flood plains, deltas, and sand