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What is slope failure and what are the two different types?
Rotational Slide Downward slipage of rocks that stay together along a concave upward slope.
Slumpes leave depressions or scars.
What are the factors that affect slope stability?
Forces acting on earth's surface pulling material toward the core of the earth.
- Sloped surface Gravity acts perpendicular(Above) and tangential to the slope.
- Flat surface Gravity acts downward as long as material is flat it will not move.
Factors of Strength?
Weight, size, shape and material on slope.
Faulting, Folding , jointing and bedding.
Water Saturation and bouyency.
What is Stress?
- Removal of lateral support
Shear Strength> Greater than Shear Stress
Shear Stress > Shear Strength
Movement down slope
What is shear stress?
- Forces applied parallel or tangential to the surface
- Main force=Gravity
- Movement depends on mass and density of material on slope and angle of the slop.
What is shear Strength?
- Forces resisting down slope movement
- Cohession among paticles sitting on the slope.
What is Mass Movement?
- Occurs when resisting forces are over come by gravitational forces.
- Resisting forces are weakend by water.
- Large scale movement downslope can occur everywhere even in the ocean.
What are Mass Movement Controls?
Slope- Movement occurs when gravity exceeds resisting forces(Frictional Resistance).
Weathering- Slope will fail or remain stable due to the amount of weathering usually considered in terms of factor of safety (Fs).
- Types of Mass Wasting
- Creep, slides, flows and slumps
What is aggradation?
Higher land elevation due to the deposition of a stream
What is loess?
Fine grained material
Cold loess-Located in U.S. and comes from glacier outwash
Warm loess-Located in China and comes from desert and is deposited in area marginal to desert.
What is a delta?
River Deltas-Landforms at the mouth of a river where it flows into an ocean, sea or lake
Forms from deposition of sediment as flow from river slows and expands upon entering,standing water, decreases transport capabilities.
What is the Milankovitch Cycles?
- Eccentricity-The shape of the earth's orbit arpund the sun. Fluctuates between more and less elliptical (o-5%). Alters distance of earth to the sun. Increase/decrease amount of radiation at surface.
- Axial Tilt-Inclination of the earth's axis in relation to its plane of orbit around the sun. 2.4 degrees change in tilt with 41,00 years.Changes radiation and high tilt=cool summer and hot winter Low tilt=hot summer and cold winter.
- Precession-Earth's slow wobble as it spins on axis. Changes every 23,000yrs. Changes times when earth is closer to the sun in the north hemisphere. Creates greater temperature contrasts.
What is a Floodplain?
Flat or nearly flat land consisting of alluvium adjacent to a stream that will eventually flood. Leaves alluvial deposits with large particle deposits closer to channel that can build levees, and fine particles draping the floodplain.
What is the Angle of repose?
Steepest angle at which a pile of unconsolidated grains remain stable and is controlled by friction.
Dry Material- angle of respose increases with increasing grain size but it usually high 20-30s.
Wet Material-Angle of repose is high because the surface tension between water and solid grains hold together.
Very Wet Material-Angle of repose is small flows like liquid. Water gets between grians.
What is Bed load?
Coarse materials (Gravel, pebbles, cobbles) that are transported along the bed of a stream by rolling(Traction, sliding and/or saltating, hopping)
What is a Head Sarp?
Displacement of land surface at upslope edge of a slump where regolith detached.
What is a Point bar?
Inner portion of meander bend that experiences slowest water velocity and revieves deposited sediment.
What is abrasion?
Wind that picks up particles and they hit each other. Similar to sandblasting. Factos-rate of abrasion, particle size, structure.
- Ventifacts-Aerody namically smoothed by wind.
- yardangs-Streamlined hill
- Hoodoo-Sculptured rocks
What is a Braided River?
If bed and suspended load exceeds stream's capacity(supply>ability to transport), sediments accumulation and stream channel builds up.
What is Secondary flow?
Flows moves side to side and up and down while still flowing downstream. (Jim Dancing).
What is a sediment Flow?
Debris flows downhill mixed with water or air
What is a Rotational Slide(Slump)?
Downward slipage of rock that stays together along concave upward slope. upper surface retains shape cohesive-undisturbed. Slumps leave depressions or scars. Isolated or in large freguent area.
What is the Factor of Safety?
Fs=sum resisting/sum driving
- Fs=1 forces are balanced
- Fs>1 slope is stable
- Fs<1 unstable slope
What is a rock fall?
Occurs when piece of rock becomes dislogged and falls down slope. May be a single rock or many. Falling rocks then hit others. Occurs in steep cliffs.
What is a talus?
Large build up of rocks which have fallen from moutains above.
What is Slides and/or Translation slides?
occurs when rock and debris slide down along a pre existing joint or bedding plane, piles of talus are common at the base of rock and debris slides.
What is a toe?
Accumulated mass of material downslope
What is the role of water?
- 1-Add water from rainfall or snow melt adds weight.
- 2-Water can change angle of repose.
- 3-Adsorption-Attachment of water molecules to minerals. Too much water and clay expands lowers cohesion. Lowers stability and strength.
- 4-Water dissolves minerals
- 5-Liquefaction-loss of grain to grain contact in sediment when it becomes oversaturated with water.
- 6-groundwater-Changes in levels of water table. fills space between grains in soil and fills fractures.
- 7-Fluid pressure- Soil and rock get buried deeper in the earth and grains rearrange to form compact structures. water fills pores and occupies the space between rocks and soil.
What is a sediment flow?
Debris flows downhill mixed with water or air. occurs when sufficent force is applied to rocks and regolith that began to flow downslope.
What is a slurry flow?
20%-40% water saturated
What is a granular flow?
0-20% water, not saturated
What is Soil Fluction?
Flowage at rates measures by cm/yr, produces lobes on hillslope. Occurs in areas where soil remains saturated with water for long periods of time.
What is a debris flow?
- Velocity various 1 meter/yr-100meters/hr
- Occurs in heavy rains or glacial
- Starts with slumps and flows down forming lobes with irregular surfaces, moves surge and pulse
- Front is heavy/large debris
- Become sless with muddy flood water
What is a mud flow?
High Fluid and High Velocity mix with sediment and water velocity and 1km/hr. Consistency ranging soup-wet concrete. Travel along streams/rivers and occur due to heavy rain. Very dangerous and travel long distance.
What is a Granular Creep Flow?
Very slow, usually continous movement of regolith down slope. Occurs in almost all slopes but rates vary. Examples bent trees, fence post and phone poles.
What isa Granular Earth Flow?
Down slope movement, thick granular materials. Similar to mudflows, though slower moving and covered with solid material carried with flow. Begin when fluid pressure is high until is supported by water lowers strength. Occurs during heavy rain. Move velocity 1-10cm/year
What is a granular grain flow?
Usually forms in dry material, sand dunes, steep slope. Small disturbances sends dry unconsolidated grains move rapidly down slope. Aeolian process.
What is a debris avalanches?
High very veolcity and large volumes of debris complete colapse of slope. Move down slope and can travel long distances along gentle slopes. Triggered by earthquakes and volcannic eruptions.
What are the three processes of rivers?
- Transport water and sediment
- Erosin disloges, dissolves and removes materials
- Deposition sand and gravel and clay
What is base level?
Level below which streams cannont erode its valley, typically corresponding with stream mouth.
What is Stream Gradient?
Rate of elevation decline in a streams from its head waters to its mouth.
What is knickpoint?
They are waterfals due to the difference between geologic deveation.
What is a streamflow?
- Mass of water located above base level in a stream has potential energy and becomes kinetic energy as gravity pulls water down.
- Rate of Conversion-depends on steepness of stream channel and volume of water.
- Stream Discharge-Volume of flow per unit of time, dictates these characteristics.
- Q=Where Discharge
- W=Channel width
- D=Channel dept
- U=Stream Velocity
what is a sheetflow?
Initial overland flow in the form of continous flim of water that moves downslope. (pulse)
What is a Rill?
Narrow, small-scale downhill grooves in topsoil resulting from erosion. (Very small)
What is a Gullies?
Large incisions that erode sharply into soil, typically on a hillside, resembles large ditch or small valley. (Large Rills)
What is hydraulic Action?
Direct removal of material by water. Water excerts sheer force as it rubs against boundaries. Water can surge into cracks and spaces to break apart material.
What is abrasion?
Chipping and gridding of sediment being transported by a river. Affects transported particles, stream bed and banks.
What is attrition?
Sediment hitting sediment/banks in transport and break.
What is Corrosin?
Chemical interaction between water and sediment. Important in bedrock streams and linestone channels.
What is competence?
Streams ability to do work. Function of velocity pf f;pw amd energy avalible to suspend particles.
What is capacity?
Measure of streams energy. Total amount of sediment stream transport. Eroded material.
What is dissolved load?
Material carried in solution by a stream. Ions, chemical weathering.
What is suspended load?
Fine grained particles (sand, silt and clay) held a loft in a stream. Turbulence (Random upward motion) holds sediment suspended.
What is a bed load?
Coarse materials (gravel, pebbles and cobbles) that are transported along the bed of a stream by rolling(traction) sliding and or saltating(hoping).
What is a meandering stream?
Sinous, curving stream that alternately erodes sediment from outside of a bend and deposits them on the sides. Snaking pattern as stream meanders/bends back and forth across floodplain.
What is a pointbar?
Inner portion of meander bend that experiences slowest water velocity and revieves deposited sediment.
What is a cut bank?
Outer bank that is subject to fastes water velocity and great erosin.
What is a pool?
Deeper area at bends of relatively fine material.
What is a riffles?
Shallower area between bends of relatively coares material
What is helical flow?
Spiraling or cork screw like flow through meander bends.
What is super elevation?
Water at surface and greater pressure at outer bank redirects flow near stream bed toward inner bank.
What is a floodplain?
Flat or nearly flat land consisting of alluvium adjacent to a stream that will eventually flood. Leaves alluvial deposits with large particle deposits closer to channel that can build levees and fine particle scraping the floodplain.
What is a Terraces?
Alluvial terraces remnant of earlier floodplains that existed at a time when a stream was flowing at a higher elevation before its channel down cut to create a new floodplain.
Is a meandering river in equilibrium?
Yes, but metastable or dynamic. depends on velocity and volume of water and the time frame is also important factor.
Describe the movement of water through a meander bend
Why dont we see more braided rivers? What is needed to create them?
Needs an over supply of coarse sediment flow.
In a stream where is the fastest velocity?
In the middle depth and width due to the lack of friction.
What is a Glacier?
Massive ice and granular snow formed by compaction and recystalization of snow, lying largely or wholly on land and showing evidence of past or present movement. Ice must be on land and have the ability to move. Changes in climate that bring about an ice age are due to the changes in seasonality and location of solar energy around the earth that occur due to malankovitch cycle.
What is glacial ice?
Begins as light fluffy snow and as more snow collects without melting it accumulates and gets heavier and compacts and melts snow below and becomes firn. Continues until firn is glacial ice.
What are the two processes of mass balance?
- Net gain at head of glacier (+)
- Middle= equalibrium (Stability)
- Bottom=loss of ice (-)
What is accumulation, ablation and deflation?
- Accumulation=adding input to mass balance
- Ablation=lost output melting on surface
- Deflation=wind flows over and picks up ice/water vapor
What is cirque?
snow filled valley in mountain
What is a valley glacier?
Fills a previous stream (fluvial valley) They are confined by the valley.
What is a tidal glacier?
Glaciers ending at the sea and it creates iceburgs through calving
What is glacial erosin process?
- Abrasion-bedrock scoured by glacier by rock debris in it
- Plucking- ice freezing to loose fractured bedrocks and extracts blocks
- Subglacial water flow- water flows at base of glacier is capable of wearing bedrock.
What is striations?
Grooves or lines on bedrock
What is polished rock?
Shinny bedrock polished from glaciers
What is grooved bedrock?
Large huge grooves in bedrock
What is an arete?
steep sided, sharp edged ridge formed from two cirques on both sides.
What is a horn?
Pyrimid shaped mountain three of arete or cirque
What is a hanging valley?
Small tributary to large valley glacier
What is a U shaped valled?
Valled with cross section that is u shaped
What is a tarn?
A lake at the bottom of a cirque
What is glacial depostion?
- Poorly sorted many particles sizes.
- Massive and free of pronounced bedding
- Composed of variety of different lithologies
- Clasts are faced striated, polished aligned by source of flow.
- Compacted due to pressure
What is lodgement till?
Deposited at the base of glaicer. Debris aligned with ice flow. Redeposited when too heavy to carry.
What is ablation till?
Deposited as the glacier receeds. Generally can be recognized due to lack of significant compaction and evidence of mass flow.
What is a Medial Moraine?
Two valley glaciers joined
What is a lateral moraine?
Formed at the edge of a valley glacier.
What is an end moraine?
Formed at the end of a glacier-pushed infront of glacier. Sediments gets piled up and hill created. Recorded as final ice advance.
What is a ground moraine?
Deposited from the base of glaciers in a non-uniformed patter.
What is a truncated spur?
Cut ridge (arete)
What is an Eskers?
Long, sinuous ridge, branching. Accumulation of sediment in opening the glacier- tunnels cavities etc. associated with subglacial river channels.
What is a Kames?
Mound like hills of layered sand and gravel superglacial depression (cavities).
What is a kettle lake?
Large ice blocks left behind by glacier when it retreated. Sediment deposited around ice block.
What is drumlins/flutes?
Elongated surface features. Large obstructions causing subglacial cavities that fill with sediment. Axis oriented with glacier movement.
What is sediment till?
Nonstratified, unsorted, angular particles
What is outwash?
Stratified well sorted well rounded sand, gravel that was deposited by stream.
What is isostatic fluctuation?
Changes in drainage networks ,incisions.
What is eustatic fluctuations?
Fjords(flooded valleys) flacial valley that goes below sea level and melting causes sea level to rise flooding creating fjords
What is deflation?
- Removal of fine material.
- Blows away loose and non-cohesive sediment