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58 Cards in this Set
- Front
- Back
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Mass Wasting
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the downslope movement of regolith and masses of rock under the pull of gravity
It is basic part of the rock cycle |
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Role of Gravity on Mass Wasting
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gravity hold objects in place by pulling on them in a direction perpendicular to the surface
tangential component of gravity acts down a slope: it causes objects to move downhill |
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Two types of stress
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Shear- the downslope component of the total stress involved
Normal- the perpendicular component |
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Angle of Repose
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The stable slope of a pile of loose particles; it is the result of the balance between gravitational forces and friction between particles
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Role of Water on Mass Wasting
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a little water increases stability, but as more water is added, stability increases as friction is reduced and failure is more likely
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Rapid Mass Movements
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Landslides and rockslides are rapid downhill movements of rock and erosional debris (rockslides are usually along bedding planes)
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Landslide Causes
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-slope oversteepened by erosion
-heavy rainfall -triggered by earthquake or some other vibration |
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Other Rapid Mass Movements
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Debris flows- thick slurry of mud, water, rock
Lahars- Occurs when volcanic activity melts glacier or snowfields Earthflows- relatively slower than rockslides and debris flows |
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Percentage of Hydrosphere that is Oceans and Nonoceans
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97.2% Oceans
2.8% is Nonocean |
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2 Possibilities for rainwater
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Infiltration- movement of water into rock or soil through cracks
Runoff- water that flows over the land |
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Hydrologic Cycle
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-Evaporation from oceans forms clouds
-Precipitation from clouds over oceans and continents -Infiltration to form groundwater -Transpiration by plants |
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Stream
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a body of water that flows downslope in a clearly defined passageway and transports particles and dissolved material
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3 Characteristics of Streams
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-Streams are part of the hydrologic cycle
-A stream runs in its channel and the sediment it carries is its load -A stream drains its its drainage basin |
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Stream Channels
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1. sheetwash downslope
2. channels form as small rills and gullies 3. tributaries develop that flow into trunk stream 4. Headward erosion occurs as stream develops |
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Streamflow discharge
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the volume of water passing a point in a given time
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Changes in Stream during flow
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-Gradient decreases
-Velocity increases -Discharge increases -Channel width and depth increase |
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Meanders
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one aspect of downstream stream behavior: consist of two parts, the point bar and the cut bank
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Floodplains
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-Built up over time by meandering river
-Broad river valleys that will periodically be covered by flood waters -Natural levees are built up along the banks of the river channel during the periodic flooding -Yazoo streams flow parallel to main channel because of natural levees |
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Braided Streams
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-Braided streams occur when the sediment load is so high, that sediments are deposited in stream channels
-Typically streams that carry meltwater from glaciers have such a high sediment load they are braided |
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Three Parts of Stream Load
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1. Bed load (too heavy for suspension)
2. Suspended load (suspended by turbulent flow) 3. Dissolved load (ions from chemical weathering) |
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What happens to grain size the further down a stream if flows?
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Grain size decreases downstream even though velocity is greater, abrasion during transport reduces size
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3 Factors of Stream Load
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1. Competence - largest grains a stream can carry
2. Capacity - how much load the stream can carry 3. Saltation - bouncing transport of sand-size grains |
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Floods
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Flooding occurs when stream overflows banks of channel and flows onto floodplain
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4 types of drainage networks
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1. Dendritic (Flat-lying bedrock)
2. Radial (Around a volcano or similar topography) 3. Trellis (Ridges of erosionally resistant bedrock) Rectangular (Due to regular joint pattern in rock) |
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Glacier
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thick mass of ice from the compaction and recrystallization of snow that shows evidence of past or present flow; glaciers move at cm's/day and km's/year
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3 types of Glaciers
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1. Valley (Alpine)
2. Continental Ice Sheet (Antarctica) 3. Ice Caps (also includes Piedmont glaciers) |
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Alpine Glacier
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glacier confined to a mountain valley
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Continental Ice Sheet
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glacier sheet flowing in all directions
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Piedmont
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One or more valley glaciers that emerge from a mountain valley and expand and create a broad sheet in the lowlands at the mountain base
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How do glaciers form?
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Formed by an accumulation of snow which is then transformed by pressure of burial into glacial ice
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Zone of Accumulation
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zone of a glacier characterized by snowfall and ice formation. Its limit is the snowline
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Zone of Ablation
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zone where ice begins to melt because of lack of snow
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Features of Valley Glacier
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-Cirque
-U-Shaped Valley -Three types of moraines 1. Medial 2. Terminal 3. Lateral |
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Glacial Erratic
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Ice transported boulders not native to its current site
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Till
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poorly sorted sediment
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5 types of Desert
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1.Subtropical (20˚-30˚N and S latitude)
2.Continental (deep in continental interiors) 3.Rainshadow (lee side of mountain ranges) 4.Coastal (cold upwelling seawater) 5.Polar (cold, dry air descends) |
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Weathering in Arid Climates
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-Chemical weathering occurs, but less important than mechanical weathering
-Soils are thinner and have soluble minerals -Not much decaying organic matter |
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Role of Water in Arid Climates
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-Water is an important erosional agent
-Wind is important in arid climate, but not as important as water -Streams are ephemeral |
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Wind Erosion
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wind is important in arid regions; it causes erodes by deflation and abrasion
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Earthquake
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Earth vibration caused by rapid release of energy; energy created by blocks slipping on faults
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Elastic Rebound Theory
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-Strain slowly builds up across fault
-Stress released when potential energy overcomes static friction -Stress is released by slip on fault -Rapid release of elastic energy (seismic waves) |
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Seismic Waves
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Body Waves consist of:
P wave (first arrival, compressional wave); and S wave (Secondary arrival Shear wave) |
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Seismometer
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Seismometer measures ground motion due to passing seismic waves
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Seismogram
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Records travel times of P and S surface waves
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Earthquake Location
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-Triangulation is used to locate earthquakes
-Find distance from each of three seismometers by S-P travel time difference |
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Earthquake Magnitude
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-Richter magnitude is based on the amplitude of ground motion
-Richter magnitude is logarithmic -Energy released with each Richter magnitude increases 30 fold -Magnitude related to size of fault rupture Mercalli scale is best on qualitative observations |
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Frequency and energy of earthquakes
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a. As size of earthquake increases, there is a
decrease in their frequency b. As Richter magnitude increases, nonlinear increase in energy released |
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4 Short Term Earthquake Prediction Methods
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1.Uplift
2.Subsidence 3.Strain 4.Electromagnetic |
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2 Long Term Earthquake Prediction Methods
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1.Statistical probability of earthquakes
2.Seismic gaps |
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Groundwater
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-Water in spaces within bedrock and regolith
-0.6% of all water on Earth -94% of all freshwater on Earth |
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The Water Table
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Water table is the top of the saturated zone in bedrock or regolith
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Water Table in Humid and Arid Environments
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-In humid environments, it intersects the surface at lakes and streams
-In arid environments, the water table is below streams and lakes |
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How does Groundwater Flow?
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-It flows from recharge area to discharge area
-It can be discharged faster than it is recharged |
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Darcy's Law of groundwater flow
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Q/A = k x h/l
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Porosity
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Porosity is the volume of rock with pore spaces; Aquifer has high permeability (and porosity)
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Permeability
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Permeability is the interconnectedness of the pore spaces (allows flow through the rock); Aquifer has high permeability (and porosity)
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Potentiometric Surface
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Water seeks its own level
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Karst Landscape
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Karst topography or landscape occurs when limestone bedrock is eroded (dissolved) by groundwater
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