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GLY1000 Final Review Mass Wasting, Streams, Groundwater, and Global ClimateKey Points:-Factors that affect the stability of a slope-Factors that affect the velocities of streams-Darcy’s LawMass Wasting:1) Mass wasting- the down slope (hill) movement of rock, soil, or sediment under the influence of gravity. a) Occurs depending onmaterials involved (rock, soil, earth, mud, or debris) AND the motion involved (fall, slide, flow)2) Landslide-all falls, slides, and flows that occur at a fast or moderately fast rate.Types of motion : - Falls: landslides that involve collapsing material from steep slopes. o Typically involve free-falling, bouncing, or rolling sediments that deposit at base of slope- Slides: downslope movement of soil/rock that occurs primarily on the surface of rupture or on thin areas of great shear strain- Flows: Turbulent motion of sediments downhillTypes of Falls:1) Rock Fall(www.bgs.ac.uk)2) Earth Fall(www.bgs.ac.uk)3) Debris Fall(www.bgs.ac.uk)*Falls occur with the detachment of soil/rock from steep slope. *Secondary Falls involve rocks already detached from cliff, just lodged upon the cliff.GLY1000 Final Review Mass Wasting, Streams, Groundwater, and Global ClimateTypes of Slides:1) Translational slidemass displaces along a wavy surface of rupture, sliding out over original surfacewww.saarc-sadkn.org2) Rotational Slidemove along surface of rupture that is curved/concave www.saarc-sadkn.org 3) Slumpbreaks off of a steep surface. Material moves as coherent mass along curved surfaces.www.geocaching.comTypes of Flows:1) Debris Flowturbulent flow of debris (cars, scrap, trees, etc.)a. Fast-moving, destroy objects in their paths, strike without warning.b. Materials vary greatly in sizec. Often triggered by heavy rains on steep slopesd. Famous debris flows: Venezuella, December, 1999 & Mt. Mayuyama, Japan 1992e. Includes Debris Avalanche2) Creep Flowslow flow (downhill) grain by grain through freeze-thaw cycles (freezing/melting) between grains of rock. Slowly “creep” 1 cm/year or less.a. Biological agents also important in creep process (insects, small animals, and plants move soil around)b. Oddly enough, results in most damage costs per year among landslides3) Mud Flowvery rapid flow of saturated plastic debris in a channel.a. Caused by high intensity rainfallb. Contains a great water content4) Earth Flowvery thick soil that accumulates and creates a flow (slow to rapid)GLY1000 Final Review Mass Wasting, Streams, Groundwater, and Global Climatea. Type of earth flow: Colorado Landslide5) Rock Flowextremely slow movements of bedrock**Factors that influence Mass Wasting/the stability of slopes:-Materials involved (rocks, soil, sediment, etc.)-Steepness of slope-Water-Vegetation-Heights-Climate (freeze-thaw cycles)-Presence and orientation of planes of weaknessa. example: a dipping/diagonal foliation can result in landslides and damage to buildings built upon the zones of weakness of a slope-Human ActivitiesStreams- Stream- water that flows in channelso Carries water and sedimentso Ability to erode/pick up sediments Erosion depends on VELOCITY- Difference between capacity of stream and competency of stream:o Capacity of stream: amount of particles stream can carry Depends on: discharge (amount of water flowing past a certain point of stream per unit time).o Competency of stream: largest particle it can carry Depends on: velocity- ***Factors that affect velocities of stream: (very important) o Gradient of stream: elevation distancehorizontal distanceor slope of surface over which it flows Steeper the slope of stream, faster the water flowsGLY1000 Final Review Mass Wasting, Streams, Groundwater, and Global Climateo Channel shape and size: (move faster with more water, ie. Added pressure)www.meted.ucar.eduo Channel roughness: Channel bed ,walls, vegetation, roots, etc. slow velocity by drag effects (friction)o Discharge: (also known as “flow”) Can be affected by:- Human activities (ex. Vegetated areas being cleared to bare soilincreases run-offcreates “flashy streams”- Channelization- when a channel is straightened by removing debris and large obstructions to increase discharge velocity.o This increases erosions and can increase flooding downstream- Dams: change the discharge by detaining the flow. Alters conditions of the stream, upstream and downstream. Velocity and discharge increase along the outside of the meander (curve/bend) creating cut-banks from erosion.- Because of this, deposition occurs on the INSIDE of the meander where velocity slow (forming point bars)- Both deposition/erosion of meanders make them more sinous(having many curves) **Graded stream (very important): carries the amount of sediments it can giventhe velocity and discharge.- Over years, slope is gradually adjusted to yield for the available discharge/velocity.-- An asymmetrical stream channel is deeper near the cut-bank and shallower near the point bar- Alluvium any stream-deposited sediment- Meander cutoff: where two meanders converge as a result of cut-banks eroding back and point-bars advancing.o Widest part of streamcutoffGLY1000 Final Review Mass Wasting, Streams, Groundwater, and Global Climate- Long Profile (of stream): represents the elevation point along the length of a streamo Closer to source, steeper the gradient- Base level: the level below which a stream cannot erodeo Sea level=ultimate base level for all streamso Characteristic of streams far above base level : V-shaped valleys Steep valley walls- Where mass wasting is faster, valley walls become less steep Actively downcutting channel and valley Absent to narrow flood plain Fairly straight channels  Steep stream gradientso Remember: high mountain streams can have local base levelstherefore take the characteristics of streams close to base levelo Characteristics of streams near base level : Contained in broad valleys Very low stream gradients (flat, long profile) Broad/complex meander belts with cutoff andoxbow lakes Flood plains much wider than meander belto Characteristics of lower course stream : Deposition is dormant Valley floor had broad flat flood plain River banks (or levees) are marked Pronounce meanders Oxbow lakes occur Estuaries/deltaso Rejuvenated stream: When a stream was once close to base level but transitions to far above base level and its energy now down cuts


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FSU GLY 1000 - Study Guide

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