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78 Cards in this Set
- Front
- Back
L2: Earth System Science
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Define earth system science:
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-Earth is a system and interactions occur between atmosphere, hydrosphere, lithosphee, biosphere, and heliosphere (space-sun to outerplanets)
-Exogenic. |
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Define a system? Give example
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-Linked/chain events lead to outcome.
ie: Fluvial systems: Variables define alluvial channel form and processes: channel: Run H20 -discharge/volume Slopes: Steep:increase velocity (gravity and vegetation decrease velocity |
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How does carbon chain have feedbacks within all parts atmosphere? What is a complexity that can change levels carbon in air?
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a) Anthrosphere: Breathe air-plants decrease CO2
b) Biosphere: Herbivores eat plants/ eaten by carnivores c) Hydrosphere: Organic waste in oceans d) Lithosphere: Dead remains Volcanic eruptions- cause cooling for climate change- chuck out idea occurring. |
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What is the purpose of models used in geomorphology and give some examples?
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-Order/ break down systems to parts
-Represent for learning A) Shape-morphological models B) Process (glacial) and response (movement) models |
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Define what atmosphere is and composition of it?
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-Gasoues sphere that envelopes the earth-gases:
N, O, CO2, H20 vapour, emissions etc |
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Give different layers of atmosphere and earth?
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1) Anthrosphere: Air breathe- we leave imprint on it- human made buildings etc
2) Heliosphere: Space between sun and other planets 3) Cryosphere: Earth surface - solid H20-ice and snow 4) Biosphere: Life zone-humans and organisms 5) Lithosphere: Solid earth crust- above/below sea- continental and oceanic- interior layers 6) Hydrosphere: H20 71% of earth 97% saline 3% fresh: -77% polar ice sheets/glaciers (slow move H20) -22% ground H20 -1% Lakes (fast move H20) |
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Why is earth considered an oblate spheroid (not circular)?
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Polar radius < equatorial radius
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What is a geoid and how is it similar to equipotential surface idea?
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Geoid: Represents mean sea level: oceans/imaginary canals on surface continent. Allows oscillations (tides)
Equipotential surface: Allows surface irregularities (bulge/depression). Ultimate base: continental erosion: Source= eorsion-continents, ocean basin deposits=sink |
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What is global hypsometry?
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Distribution of heights above/below sea level ( trenches)
-Frequency distribution -Bimodal (above/below) -Continental platforms/ ocean basins (71% earth) |
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What are some major morphological features?
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a) Orogenic moutnain belts- Andes
b) Rift valleys (pull apart volcanoes near Africa) c) Continental shelf (New Guinea) d) Continental slope e) Mid Ocean ridge f) Trench (Chile)-6000m deep g) Island Arc: Indonesia-volcano chain |
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What is isostasy?
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State of balance of the earths crust-lighter continental masses float denser substratum-buoyancy.
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What are 2 theories on why issostasy occurs and give 2 examples of where it occurs on earth?
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Pratt model: Part crust stands higher because lower density
Airy model: Part crust stands higher as lower density and increasing thickness. eg: Mountains after mountain building: -Erode (unloads weight-uplift) -Sediment to oceans -Overall balances: bulge in ocean instead Icebergs: Ice uplifted as ice has 0.1 lower density than water. |
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What is importance of plate tectonics?>
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Most recent theory unifying nature earths crust.
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What did Wegener find out?
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Fit, rock type/climate, palaeontology
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What is palaeomagnetic evidence for plate tectonics>?
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Remanent magnetism
-Apparent polar wandering |
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What is evidence of Gondwana breakup?
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Plate tectonics, continental geography, fossils.
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What is the plate tectonic theory/model?
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-7 major paltes: Antractica, North and South America, Pacific, Indo-Aussie, African, Eurasian
-Plates move relative to eachother and earths axis (70 mm per year) |
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What are different plate boundary types?
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Divergent, destructive, collision, transform= exert influence on geomorphology expressed.
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L3: Geomorphology of plate margins:
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What is the significance of plate tectonics and give examples?
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Significance: Form landscapes
eg: Sthern Alps: Plates slide (mtns interact with ciruclation system-Westerly)- orographic rainfall=14000mm/yr rain, very fast change landscape- erosion 10x normal rate. |
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What are the 2 types (with parts) of mrchanisms of plate motion?
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-Shallow convection/upper/ whole convection (Thermal)
-Ridge push, slab pull , gravity sliding ( mechanical) Hence: Thermal mechanical process. |
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What are the 3 different types/ conditiosn and associated features for plate boundary interactions?
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a) Divergent:
-Spreading margins -Tensional (pull and rip) stresses dominate eg: Sea floor spread/rift-volcanoes (lava moves away from pull apart area) b) Convergent: -Compressional stresses (push together-crumple) -Subduction -Collision orogens c) Transform -Shear stresses (edges slide- strike-slip) -Compression too/convergence (oblique slip margins)-transform margins |
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What are the different types for convergent plate interaction?
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a) Oceanic-oceanic
b) Oceanic-continental c) Continental-continental |
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Explain what occurs at an intercontinental boundary (continent-continent)?
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-Passive continental margin ( transition between oceanic / continental not active plate margin)
Evolves to: -Active margin -Suture zone (subducting)-2 continents weld eg: Himilayas |
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What occurs intra -oceanic island arc (oceanic-oceanic)?
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-Subducting oceanic plate-trench
-Heat of plate: rising magma (igneous intrusions/eruptions) -Morphologically distinct: fore/volcanic/back arcs eg: Western Pacific (Solomon and Bismark arcs) |
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What occurs at continental margin orogen ( oceanic- continental)?
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-Subduction oceanic below override continental
-Frictional heating-rise magma plume (increase orogenic belt) -Granite intrusions eg: Olympic Mountains |
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Describe features of the Andes mountain range?
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-9000km long, >5000m high
-Granite intrusions -Substantial uplift (>900 volcanoes) -Melting (subduction zone) |
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What is the Southern Alps an example of and describe some key stats on the movement of the plate/plate arrangements in area?
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-Transform fault:
Average motion= 40mm/yr transform, 22mm convergence (dominant is vertial uplift) Alpine fault- 2 subduction zones a) North= Pacific plate subducted b) South=Indo Aussy. |
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Lecture 4: The Geomorphologists toolbox
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Define geomorphology?
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Transdisciplinary
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What are 2 views of what geomorphology is, give examples?
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a) What geomorphologists do:
-Dictated by past practice looking at ecogenic structures on earth-processes related -Scale determined by problem to solve b) Field survey: Map landforms ( always better resolution) -Data resources: Topography, aerial photos, satellite remote sensing. eg: -Mt Taranaki: Radial draiange patterm-increase density and contour shade with higher altitude -Spot: colour attributed to wavelength -Infrared -Geological/geomorphic maps combined -Major landforms , colour for age of landforms combined. |
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What is Lidar and some applications for each version?
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LIDAR=Light + radar
-Measure distance (pt target) -Scan (analyse reflected light) -Illuminate targets 2 main applications: a) Ground (terrestrial scanner)= -Photo over groun taken geomorphological model-picks 10mm change in cliff -safety in mines (volume removed and bulges --Glaciers :calving events b) Airborne ( overland- move side to side aeroplane) -Impact active tectonis on land:GPS strike slip fault-river movement -West coast: costly to filter topography with trees out of it -Apline fault details |
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What is GPR?
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Ground Penetrating Radar:
-Small, remote sensing -Use: Over 2 beach ridge crests=also take care make more accurate. -Core taken be more accurate. |
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What are the two ways to date events and landforms on earth?
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a) Relative dating: Sequence landforms/ events (comparison)
b) Numerical dating: Numerical age -land/events= Geochronology ( Earth age model) |
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Describe the use of radiocarbon dating?
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14C
-Plants create 14C via photosynthesis -Things eat plants- die and decay -Concentration of Carbon with 1/2 life of carbon known when decaying to 14/7 N, can see age. |
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What are some problems with radiocarbon dating?
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a) Radiocarbon concentration atmosphere varies in time
B0 Different parts biosphere/ hydrosphere different cycling times ( beside river inject C) |
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What is exposure age dating/
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-Cosmic rays hit rocks- produce rare and measurable nuclides (concentration tells age)
-Use of low concentration determination measurer Time: Few 100 to 100,000 years. |
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What is an example of meauring process rates/
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-Sediment rating curves ( discharge record: record sediment transport/ erosion)
-Regression equation: Qs (discharge sediment)- a (constant) x Qb(power) |
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What are problems with sediment rating curves?
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-Sediemnt generation doesnt equal sediemnt yield.
Generation=rate sediemtn forms/erodes Yield= rate sediement exported-different storage/reycling -Bed load-10% in N.Z. |
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Measuring process rates-what does this involve?
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-Erosion rates longer time scales (10^6-10^8 yrs)
-Thermochronometry -Measure erosion/uplift: millions to 10's millions yrs -Time/temp histories- rocks (argon/Helim fission)- start minerals cool below closure temp -Combine with known thermal gradient earth- long term erosion Problem: Substantial uncertainties. |
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L7: Mass Movement 1:
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What are the uses of a hydrograph?
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-Basic analysis stream flow: discharge vs time
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What are chemo and sedigraphs?
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-Chemograph: anticlockwise hysteresis: concentration ions/chems water is biggest at 1st stage-1st injected into system as old
Sedigraph: Most at start-deposit of sediment built up-gets less. (clockwise hysteresis) |
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What are 3 different runoff types?
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a) hortonian overland flow
b) Saturated zone overland flow c) Subsurface storm flow |
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What are the 4 diffusive (gravity driven) slope processes?
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a) Slope erosion: material erodibility vs erosive pwoer: transprot rate proportional t slope
eg: Ross creep-vege help stabilitse and decrease effect steep slope b) Raindrops: Break down soil, splashes break down, turbulence sheet flow c) Sheetwash: Roll ground (traction d) Soil creep: Increase down slope movement (freeze-thaw) ALL= POTENTIAL TO KINETIC ENERGY Weathered materials off slope |
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What are 2 forms of water flow landscape formations?
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1) Rills:
-Conc sheet wash -Depth for turbulence -Entrain larger particles -<0.5m Gullies: >0.5m (size distinguished) -Unconsolidated seidment |
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What is the difference between diffusive and advective processes/ what do they both contribute to?
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Diffusive: gravity driven/slope angle
Advective: Water flow driven/ dependent discharge /slope |
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What are 3 constituents of shear strength?
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a) Friction: angle:max angle different for cohesiveness particles
b) Effective normal stress (90 degrees plane slide-pores included with upward pressure) c) Cohesive forces: electromechanical-binding |
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What is the coulomb shear strength equation?
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s (Shear strength)= σ' (effective normal stress) x tan(φ)-coefficient plane sliding friction
With cohesion included: S=c+σ'.tan(φ) |
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What is the shear stress equation?
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T (shear stress)= ps (soil density) x g(gravitational accleration) x zs(soil thickness) x sinѲ (slope angle)
Constants: gravity, slope, soil thickness, so overall shear stress generally constant over time. |
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What is the factor of safety, and what does it tell us?
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F=Σ R (resist force) / ΣD (driving force)
F=1 (equilibrium) F<1 (failur slope F>1 ( stability) |
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What are the uses for factor of safety/what does it consider?
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-Summarises controls of slope stability:
a) Material properties (density H20/soil, cohesion, angle friction) b) Geomorphic characteristics ( soil depth/slope) c) Time variant conditions: (proportion soil thickness saturated and pore H20 pressure) d) gravitational acceleration. |
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What are the five main parts of the infinite slope model?
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1) Resisting shear strength
2) Pore pressure upwards from soil 3) Driving shear stress 4) Effective normal stress downwards 5) Slope angle of failure plane. |
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What is infinite slope model usually used for?
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- Analyze stability of slopes to shallow, planar landslides.
-Balance: shear strength-slope materials, shear stress-gravity- downslope orientated component of mass of soil. -Considers pore pressure /slope effect. |
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L8: Mass Movement #2:
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What are the different components of slopes- regoliths on them with water?
i f p b |
i=rain intensity
f=infiltration rate p=percolation rate b=breadth across slope |
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How do we calculate volume of regolith and give example of how to calculate remaining available capacity?
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Volume regolith=2bh
Porosity (n): capacity hold H20=n (2hb) ie: Assume n=0.5 z=0.6 Block capacity therefore =0.3 m^3 Field capacity at start (20% pore space filled with H20)- capacity inflitrate new H20= (0.8) x (0.3)=0.24m (left over to be filled) -Antecedent moisture can play large role |
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What are the 3 types of mass movement?
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a) Type of movement (rock fall vs slide)
b) Velocity (fast: creep vs rock avalanche) c) Water content |
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What are 3 types of mass movement?
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a) Pure flow: Different rate displacement across structure
b) Pure slide: Equal rate displacement c_ Pure heave: Ice/H20 expand and contract |
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What are the 5 different parts of Varnes'(1975) classification?
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1) Fall: Steep faces-airborne
2) Topple 3) Slides (failure well defined shear plane, translational/rotational 4) lateral spread 5) Flow (shear throughout moving mass) |
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What are 2 types of materials/forms on slope?
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1) colluvium: Unconsolidated material slopes
2) Tallus (scree): Particles bottom cliff physical weathering. |
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What degree/where is soil cover on following slopes?:
Convex, concave, straight, compound? |
Convex: top (diffusive weathering dominated gravity)
Concave: Hydraulic processes: advective H20 Straight: Mass movement dominated (also H20) Compound: Mixture of all. |
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What is the impact of resistant rock on slope profile?
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-Rock strength controls output of slope, not processes as usual
-Strength equilibrium slopes: units with characteristic angles -Structural slopes: Controlled rock structure |
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What are the two main slope type forms?
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a) Weathering limited slopes: Weathering rate< transport capacity, no/thin regolith
b) Transport limited slopes: Weathering> transport (thick regolith). |
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What is the interaction between slopes and fluvial system?
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-Hydro transfers
-Material (sediment) transfers 1) Rcok weathering 2) Slope processes=mass wasting 3) iver transported debris. |
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L9: Fluvial Processes # 1:
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What are the 2 opposing flows within water?
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Gravity (accelerate and channel slope)
vs Resisting (frictional) forces |
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What are the 4 main different flow characteristics?
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a) uniform/ non-uniform flow: Constant velocity in space/ varies in space: velocity gets greater closer to middle vs velocity swayed to one side on corner.
b) Steady/unsteady flow: Velocity constant in time (linear relationship) vs varies in time (unsteady oscillating trend) c) Laminar/turbulent flow: Laminar=each element moves specifc path with uniform velocity-no real mix. shear stress distributed. Turbulent: shear stress mixed. d) Tranquil /rapid flow: (Critical/subcritical flow)-determines flow natue and forming bedforms channel floor. |
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How do you work out laminar vs turbulent flow?
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Work out using Reynolds eqn:
Re (Reynolds #)= v (flo velocity) x R (Hydraulic radius or H20 depth)/ V (Kinematic viscosity) Re<500=laminar 500<Re<2500= Transitional flow Re>2500=turbulent flow |
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how do we work out if critical or subcritical flow?
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use Froude # eqn:
F (Froude #)= v (flow velocity)/ SQRT g( Acceleration) x d (depth flow) F<1= subcritical/tranquil F>1=supercritical/rapid F=1: Flow critical. |
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What is the difference between hydraulic jumps and drops?
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Hydraulic jump:
-Go from supercritical to subcritical -No change discharge/v -Rapid, shallow to deeper, slower= slower H20 (decelerates) Hydraulic drop: Subcritical to supercritical -Acceleration |
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What is flow velocity influenced by and how does it vary within channel?
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Influenced by: Gradient, roughness, channel cross-sectional area.
Velocity-channels varies 4 directions: -With depth -Downstream -Across stream -With time |
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What is flow resistance?
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-Water: deformation fluid resistance (viscosity-molcule movement)
-3% energy H20 left after friction for sediment transport -Change viscosity with change sediment conc. |
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What are the 3 different equations used to measure flow resisitance?
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Chezys equation:
C (Chezy coefficient)= v (mean flow v) x SQRT R(hydraulic radius) x s 9Channel gradient) Mannings equation: v(mean flow velocity)= R (hydraulic radius)^0.66 x s (channel gradient)^0.5 / n Mannings roughness eqn -usually betweeen 0.02 and 0.06) Controls for mannings dependent river- organic matter, banks, boulders etc. Darcy-Weisbach eqn: ff( Darcy-Weisbach roughness coefficicent)= 8g (gravity acceleration) x R( hydraulic radius) x s(Channel gradient)/ v(mean flow velocity)^2 |
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How do we work out hydraulic radius (R)?
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R -Cross sectional depth/wetted perimeter
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What are the different resistance variables in flow carrying sediemnt?
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-Grain/ surface rougness
-Form roughness -Channel irregularirites -Suspended materials in flow |
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What are the 3 important stream energy constituents?
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a) potential energy: PE=m (mass) x g (gravity accleeration) x h (height above base level)
b) Kinetic energy: KE =0.5 m (mass) x v^2 (velocity) c) thermal energy. |