pg lecture 13 -weathering and mass wasting 113016
TRANSCRIPT
![Page 1: Pg lecture 13 -weathering and mass wasting 113016](https://reader036.vdocuments.site/reader036/viewer/2022062822/58811c631a28abb9388b60c3/html5/thumbnails/1.jpg)
Weathering and Mass Weathering and Mass WastingWasting
Chapter 10
![Page 2: Pg lecture 13 -weathering and mass wasting 113016](https://reader036.vdocuments.site/reader036/viewer/2022062822/58811c631a28abb9388b60c3/html5/thumbnails/2.jpg)
External vs. Internal ProcessesExternal vs. Internal Processes(the dynamic equilibrium model)(the dynamic equilibrium model)
![Page 3: Pg lecture 13 -weathering and mass wasting 113016](https://reader036.vdocuments.site/reader036/viewer/2022062822/58811c631a28abb9388b60c3/html5/thumbnails/3.jpg)
DenudationDenudation—Large-scale removal of —Large-scale removal of material that lowers the overall profile of material that lowers the overall profile of the topographythe topography
![Page 4: Pg lecture 13 -weathering and mass wasting 113016](https://reader036.vdocuments.site/reader036/viewer/2022062822/58811c631a28abb9388b60c3/html5/thumbnails/4.jpg)
Denudation ProcessesDenudation Processes
• Weathering—Rock disintegrating in place• Mass wasting—Eroded rock moving
downslope• Erosion—Extensive removal of rock material,
generally transported long distances
![Page 5: Pg lecture 13 -weathering and mass wasting 113016](https://reader036.vdocuments.site/reader036/viewer/2022062822/58811c631a28abb9388b60c3/html5/thumbnails/5.jpg)
The Grand CanyonThe Grand Canyon
![Page 6: Pg lecture 13 -weathering and mass wasting 113016](https://reader036.vdocuments.site/reader036/viewer/2022062822/58811c631a28abb9388b60c3/html5/thumbnails/6.jpg)
WeatheringWeathering
• The combined action of all atmospheric and biologic processes that cause rock to disintegrate physically and decompose chemically because of exposure near Earth’s surface
• Changing bedrock into regolith
![Page 7: Pg lecture 13 -weathering and mass wasting 113016](https://reader036.vdocuments.site/reader036/viewer/2022062822/58811c631a28abb9388b60c3/html5/thumbnails/7.jpg)
Weathering of BedrockWeathering of Bedrock► Wherever bedrock is Wherever bedrock is
exposed to the natural exposed to the natural elements, it weatherselements, it weathers
► Any crack, joint, or Any crack, joint, or cavity in the rock will cavity in the rock will allow weathering allow weathering agents to penetrate agents to penetrate and break it apartand break it apart
![Page 8: Pg lecture 13 -weathering and mass wasting 113016](https://reader036.vdocuments.site/reader036/viewer/2022062822/58811c631a28abb9388b60c3/html5/thumbnails/8.jpg)
As rocks weather, surface area increases, offering more surfaces to be weathered…
![Page 9: Pg lecture 13 -weathering and mass wasting 113016](https://reader036.vdocuments.site/reader036/viewer/2022062822/58811c631a28abb9388b60c3/html5/thumbnails/9.jpg)
…producing this result.
![Page 10: Pg lecture 13 -weathering and mass wasting 113016](https://reader036.vdocuments.site/reader036/viewer/2022062822/58811c631a28abb9388b60c3/html5/thumbnails/10.jpg)
1010
Mechanical WeatheringMechanical Weathering
• Physical disintegration of rock as a result of natural phenomena, without a change in its chemical composition
![Page 11: Pg lecture 13 -weathering and mass wasting 113016](https://reader036.vdocuments.site/reader036/viewer/2022062822/58811c631a28abb9388b60c3/html5/thumbnails/11.jpg)
Mechanical WeatheringProcesses
• Frost wedging• Salt wedging• Unloading/pressure-release jointing• Thermal expansion and contraction• Biologic weathering
![Page 12: Pg lecture 13 -weathering and mass wasting 113016](https://reader036.vdocuments.site/reader036/viewer/2022062822/58811c631a28abb9388b60c3/html5/thumbnails/12.jpg)
Frost Wedging
Most effective where there is repeated freeze and thaw, as in arctic or tundra environments
![Page 13: Pg lecture 13 -weathering and mass wasting 113016](https://reader036.vdocuments.site/reader036/viewer/2022062822/58811c631a28abb9388b60c3/html5/thumbnails/13.jpg)
Frost Wedging
![Page 14: Pg lecture 13 -weathering and mass wasting 113016](https://reader036.vdocuments.site/reader036/viewer/2022062822/58811c631a28abb9388b60c3/html5/thumbnails/14.jpg)
Salt Wedging
• Most effective in coastal environments and semi-arid environments
Honeycomb,or “tafoni”, Salt Point, Sonoma Coast
![Page 15: Pg lecture 13 -weathering and mass wasting 113016](https://reader036.vdocuments.site/reader036/viewer/2022062822/58811c631a28abb9388b60c3/html5/thumbnails/15.jpg)
17
Unloading or Pressure-release jointing
• Rock brought near the surface relieves confining pressure and allows the rock to expand slightly, forming cracks
![Page 16: Pg lecture 13 -weathering and mass wasting 113016](https://reader036.vdocuments.site/reader036/viewer/2022062822/58811c631a28abb9388b60c3/html5/thumbnails/16.jpg)
Thermal Expansion and Contraction
Most effective in regions with large differences in temperature between daily highs and nightly lows
![Page 17: Pg lecture 13 -weathering and mass wasting 113016](https://reader036.vdocuments.site/reader036/viewer/2022062822/58811c631a28abb9388b60c3/html5/thumbnails/17.jpg)
Thermal Expansion and Contraction
![Page 18: Pg lecture 13 -weathering and mass wasting 113016](https://reader036.vdocuments.site/reader036/viewer/2022062822/58811c631a28abb9388b60c3/html5/thumbnails/18.jpg)
Biologic WeatheringGrowth of plant roots, burrowing animals loosen and break apart rocks
![Page 19: Pg lecture 13 -weathering and mass wasting 113016](https://reader036.vdocuments.site/reader036/viewer/2022062822/58811c631a28abb9388b60c3/html5/thumbnails/19.jpg)
Chemical Weathering
• Rocks forming at depth are stable under those conditions
• Once rocks are exposed to surface conditions many of the minerals become less stable and may undergo a slow chemical change that weakens their internal structures
![Page 20: Pg lecture 13 -weathering and mass wasting 113016](https://reader036.vdocuments.site/reader036/viewer/2022062822/58811c631a28abb9388b60c3/html5/thumbnails/20.jpg)
Chemical Weathering
• Decomposition of rock thorough the chemical alteration of its minerals– Air, soil water solutions, and groundwater
solutions contain dissolved oxygen, carbon dioxide, or other reactive elements
– Water is the greatest agent of chemical weathering
– Chemical weathering is most effective in warm, moist climates
![Page 21: Pg lecture 13 -weathering and mass wasting 113016](https://reader036.vdocuments.site/reader036/viewer/2022062822/58811c631a28abb9388b60c3/html5/thumbnails/21.jpg)
Chemical Weathering:The Influence of Temperature and
Precipitation
![Page 22: Pg lecture 13 -weathering and mass wasting 113016](https://reader036.vdocuments.site/reader036/viewer/2022062822/58811c631a28abb9388b60c3/html5/thumbnails/22.jpg)
Oxidation• Oxygen dissolved in soil water or ground water can
bond with the chemical elements of the minerals to form new minerals
• Iron (Fe) turning to rust (Fe2O3) in the presence of oxygen and water
![Page 23: Pg lecture 13 -weathering and mass wasting 113016](https://reader036.vdocuments.site/reader036/viewer/2022062822/58811c631a28abb9388b60c3/html5/thumbnails/23.jpg)
Hydrolysis and HydrationHydrolysis--Water combines with some minerals, breaking down the rocks into new mineral compounds
granite: fedspar turns to clays + quartz sandcontributes to spheriodal weathering
![Page 24: Pg lecture 13 -weathering and mass wasting 113016](https://reader036.vdocuments.site/reader036/viewer/2022062822/58811c631a28abb9388b60c3/html5/thumbnails/24.jpg)
Hydrolysis and HydrationHydration--Water molecules become part of the chemical composition of the rock (no breakdown). Mineral alteration and expansion results in grain-by-grain destruction of rocks.
Formation of gypsum from anhydrous calcium sulfate (the mineral anhydrite) which has absorbed water into its chemical structure
![Page 25: Pg lecture 13 -weathering and mass wasting 113016](https://reader036.vdocuments.site/reader036/viewer/2022062822/58811c631a28abb9388b60c3/html5/thumbnails/25.jpg)
Carbonic Acid
Limestone and marble are most susceptible to this type of weathering
Carbon dioxide dissolved in water creates a weak acid called carbonic acid which can dissolve some minerals, especially calcium carbonate
![Page 26: Pg lecture 13 -weathering and mass wasting 113016](https://reader036.vdocuments.site/reader036/viewer/2022062822/58811c631a28abb9388b60c3/html5/thumbnails/26.jpg)
Acid Precipitation
• In urban areas with pollution from sulfur and nitrogen oxides, these gasses can mix with atmospheric water, forming acid precipitation
• Dissolves limestone and marble and other types of building stones
![Page 27: Pg lecture 13 -weathering and mass wasting 113016](https://reader036.vdocuments.site/reader036/viewer/2022062822/58811c631a28abb9388b60c3/html5/thumbnails/27.jpg)
Organic AcidsDecaying vegetation mixes w/ water to form soil water w/ complex organic acids that can react to dissolve or chemically alter minerals
![Page 28: Pg lecture 13 -weathering and mass wasting 113016](https://reader036.vdocuments.site/reader036/viewer/2022062822/58811c631a28abb9388b60c3/html5/thumbnails/28.jpg)
Mass WastingMass Wasting
Spontaneous downslope movement of soil and eroded rock fragments under the influence of gravity, but without the action of moving air, water or ice
![Page 29: Pg lecture 13 -weathering and mass wasting 113016](https://reader036.vdocuments.site/reader036/viewer/2022062822/58811c631a28abb9388b60c3/html5/thumbnails/29.jpg)
Angle of ReposeThe steepest angle that loose fragments can lie without movement if undisturbed
![Page 30: Pg lecture 13 -weathering and mass wasting 113016](https://reader036.vdocuments.site/reader036/viewer/2022062822/58811c631a28abb9388b60c3/html5/thumbnails/30.jpg)
![Page 31: Pg lecture 13 -weathering and mass wasting 113016](https://reader036.vdocuments.site/reader036/viewer/2022062822/58811c631a28abb9388b60c3/html5/thumbnails/31.jpg)
Mass Wasting
• The type of mass wasting event that occurs will depend upon speed and the degree of saturation
![Page 32: Pg lecture 13 -weathering and mass wasting 113016](https://reader036.vdocuments.site/reader036/viewer/2022062822/58811c631a28abb9388b60c3/html5/thumbnails/32.jpg)
Mass Wasting(another view)
![Page 33: Pg lecture 13 -weathering and mass wasting 113016](https://reader036.vdocuments.site/reader036/viewer/2022062822/58811c631a28abb9388b60c3/html5/thumbnails/33.jpg)
Types of Mass Wasting
• Rock fall• Rock slide and
Topple
• Debris flow• Earth flow• Mudflow
• Slump• Solifluction• Creep
• Induced mass wasting
![Page 34: Pg lecture 13 -weathering and mass wasting 113016](https://reader036.vdocuments.site/reader036/viewer/2022062822/58811c631a28abb9388b60c3/html5/thumbnails/34.jpg)
Rock Fall
Talus slopes—Regolith which has fallen down steep slopes, funneled into “blankets” of rock called talus cones
Fresh slopes are very unstable
![Page 35: Pg lecture 13 -weathering and mass wasting 113016](https://reader036.vdocuments.site/reader036/viewer/2022062822/58811c631a28abb9388b60c3/html5/thumbnails/35.jpg)
Rock Fall
![Page 36: Pg lecture 13 -weathering and mass wasting 113016](https://reader036.vdocuments.site/reader036/viewer/2022062822/58811c631a28abb9388b60c3/html5/thumbnails/36.jpg)
Rock Slide
![Page 37: Pg lecture 13 -weathering and mass wasting 113016](https://reader036.vdocuments.site/reader036/viewer/2022062822/58811c631a28abb9388b60c3/html5/thumbnails/37.jpg)
Mudflow and Debris Flow
• Mudflow—Rainwater mixed with soil flowing very quickly downslope as a river of mud
• Debris flow—More rock fragment than mudflow, but similar in other characteristics
![Page 38: Pg lecture 13 -weathering and mass wasting 113016](https://reader036.vdocuments.site/reader036/viewer/2022062822/58811c631a28abb9388b60c3/html5/thumbnails/38.jpg)
Earthflow• Water-saturated soil or
rock material• Moves a limited distance
down slope as one large mass
• Generally slower in motion (over the course of hours)
• Common form of earth movement causing road closures and property destruction during heavy rains
![Page 39: Pg lecture 13 -weathering and mass wasting 113016](https://reader036.vdocuments.site/reader036/viewer/2022062822/58811c631a28abb9388b60c3/html5/thumbnails/39.jpg)
Near La Conchita Slide, alongHwy. 101 in Ventura County
![Page 40: Pg lecture 13 -weathering and mass wasting 113016](https://reader036.vdocuments.site/reader036/viewer/2022062822/58811c631a28abb9388b60c3/html5/thumbnails/40.jpg)
La Conchita Slide (Earthflow)Hwy. 101, Ventura County
![Page 41: Pg lecture 13 -weathering and mass wasting 113016](https://reader036.vdocuments.site/reader036/viewer/2022062822/58811c631a28abb9388b60c3/html5/thumbnails/41.jpg)
La Conchita Slide (Earthflow)Hwy. 101, Ventura County
![Page 42: Pg lecture 13 -weathering and mass wasting 113016](https://reader036.vdocuments.site/reader036/viewer/2022062822/58811c631a28abb9388b60c3/html5/thumbnails/42.jpg)
Slump—Slow, concave sliding
![Page 43: Pg lecture 13 -weathering and mass wasting 113016](https://reader036.vdocuments.site/reader036/viewer/2022062822/58811c631a28abb9388b60c3/html5/thumbnails/43.jpg)
Slump
![Page 44: Pg lecture 13 -weathering and mass wasting 113016](https://reader036.vdocuments.site/reader036/viewer/2022062822/58811c631a28abb9388b60c3/html5/thumbnails/44.jpg)
Slump
![Page 45: Pg lecture 13 -weathering and mass wasting 113016](https://reader036.vdocuments.site/reader036/viewer/2022062822/58811c631a28abb9388b60c3/html5/thumbnails/45.jpg)
Solifluction
• Continuous freeze and thaw cycles slowly move weathered particles downslope
• Over time, the entire slope moves downhill
![Page 46: Pg lecture 13 -weathering and mass wasting 113016](https://reader036.vdocuments.site/reader036/viewer/2022062822/58811c631a28abb9388b60c3/html5/thumbnails/46.jpg)
Solifluction
![Page 47: Pg lecture 13 -weathering and mass wasting 113016](https://reader036.vdocuments.site/reader036/viewer/2022062822/58811c631a28abb9388b60c3/html5/thumbnails/47.jpg)
Solifluction
![Page 48: Pg lecture 13 -weathering and mass wasting 113016](https://reader036.vdocuments.site/reader036/viewer/2022062822/58811c631a28abb9388b60c3/html5/thumbnails/48.jpg)
Solifluction LobesEmphasized by Animal Trails
![Page 49: Pg lecture 13 -weathering and mass wasting 113016](https://reader036.vdocuments.site/reader036/viewer/2022062822/58811c631a28abb9388b60c3/html5/thumbnails/49.jpg)
Soil Creep
![Page 50: Pg lecture 13 -weathering and mass wasting 113016](https://reader036.vdocuments.site/reader036/viewer/2022062822/58811c631a28abb9388b60c3/html5/thumbnails/50.jpg)
Induced Mass Wasting
Mass wasting caused by human activity