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149 Cards in this Set
- Front
- Back
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Dating techniques
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relative dating and absolute dating
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relative dating
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establishment of age of a feature relative to the age of another feature: original horizontality, superposition, cross cutting relationship
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Original horizontality
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Sediment were deposited in vast horizontal sheets
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age equivalance of rock layers
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strata from different places can be established using fossils
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superposition
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sequence of sedimentary rock layers-younger rocks are at the top and older rocks are at the bottom
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cross cutting relationship
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feature cutting through another feature must be younger than the feature it cuts through
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absolute dating
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used to establish the exact age of a feature-may date rock formation and rock metamorphsis
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radiometric dating
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use of constancy dcay rates of radionuclei to calculate year of their origin
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half life
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the constant time required for 1/2 of the amount of a parent isotope to decay into a daughter
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commonly used isotopes
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40K40Ar-1.3 billion 238U206Pb-4.5 billion
14C14N-5730 yrs-organic |
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Dating ranges
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1/10-10x's the half life
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Dendrochronology
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tree ring dating
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Precambrian Eon
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4500 mya to 540 mya-most of earth history-rocks mostly in continental cratons-atomosphere little oxygen until phtosyntheic plants-early fossils prokaryotic bacteria and algae-stromatolites
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Paleozoic Era
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540-248 mya early, mid late, and end
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Early Paleozoic
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orgnisms diversity and abundance-trilobites and fishes, fossils
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Mid Paleozoic
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Fishes dominate, first land plants, and insect fossils
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Late Paleozoic
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Pangea formed early app mtn chain
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End Paleozoic
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massive extinciton of many marine animals
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Mesozoic Era
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248-65mya triassic, jurassic, cretaceous
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Early mesozoic
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break up of pangaea-triassic-gymnosperams and dianosaurs-first mammals
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Late mesozoic
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sierra nevada batholith, rocky mtns.
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End of Mesozoic
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massive extinction-perhaps meteorite impact in Yucatan
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Cenozoic
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65 Mya-present-Early Mid Late
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Early Cenozoic
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Mammals and angiosperms become dominant
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Mid Cenozoic
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Alpine-Himalayan
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Late Cenozoic
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Pleistocene-glaciation begins
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Late Cenozoic Pleistecene/Holocene boundary
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megafauna extinctions (wooly mammoth, giant sloth)
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Global water balance
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ocean contain most water on earth, ocean main source of percip, other (glaciers and groundwateR)
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Run off
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water flowing over the land surface rather than soaking in below ground
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Groundwater
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Largest freshwater reservoir available to humans
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Groundwater Dist.
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Zone of aeration, zone of saturation, aquitard, aquifer, perched water table
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Zone of aeration
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contains a mix of air and water in pore spaces
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Zone of saturation
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all pore spaces fille w/ water, top of zone is water table
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aquitard
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rock material body that hinders water move.
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aquifer
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rock material containing retrievable water-transmits water freely. unconfined/confined
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Unconfined aquifer
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not overlain by an aquitard
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confined aquifer
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both underlain and overlain by aquitards
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Perched water table
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zone of saturation above the regional water table creaed by an aquitard.
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Groundwater movement
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depends on porosity, permeability, water table slope-mm's to a few cm's per day
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Porosity
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voume of por space in rock material
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permeability
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ability of a rock material to transmit fluid
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Water table slopes
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drop in elevation of the water table divided by the distance over which this drop occurs
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Artesian flow
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springs and wells that discharge water freely
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Issues w/ groundwater
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availability, pollution, land subsidence, groundwater mining
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availability groundwater
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number of houses using water
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pollution of ground water
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sewage leak in if too many houses close together
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mining
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ground collapse due to excessive water mining
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polygenetic
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reason for extinction due to climate change-change in environment-human population-disease
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Milan Kovitch hypothesis of Ice age
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periodicy in 3 orbital characteristics-oribital eccentricity, axial tilt variation, and precession
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Orbital eccentricity
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10,000 yr cycle-changes in ellipticalness-low eccentricity less change in season
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Axial tilt variation
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22-24.5 degrees 41,000 yr cycle-low tilt less sesaonality
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Precession
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Northern Hemi tilted away from the sun-less seasonality 26,000 yr cycle
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Moisture of NC
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comes from Gulf of Mexico
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Transpiration
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plants take water from soil release into the air
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Occurance of artesians
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areas of tiled rocks enter ground flow down-build pressure because of aquifer bt two aquitards cause bubbling-drill through aquitard to get to aquifer
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Weathering
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the physical breakdown and chemical alt. of rocks at or near the earth's surface
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Mechanical/Physical weathering
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breaking of rock into smaller pieces via natural physical forces w/o changin the rock's mineral comp.
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Chemical weathering
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chemical transformation of rock into one/more new compounds: almost always requires water
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Soil
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rock detritus at the sruface of the earth that has been weathered by physical and chemical, and biolic process so it supports growth of plants
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Soil Horizons
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A horizon, B horizon and C horizon which all develop together-layers do not indicate age
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A horizon
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mineral rich-organic water breakdown zone of loss which gets washed to B
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B horizon
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strongly red in NC-receives nutrients from A roots of plants lost at the end of B
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C Horizon
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unaltered parent material which forms the other layers
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Karst Topography
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Terrain w/ distinctive landforms and drainage arising from geater rock solubility in natural water than is found elswhere-create caverns/sinkholes-
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Running Water
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Most important agent of land surface changes. Organized within drainage basins-catchment, drainage divides, channel network,hillslopes
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Catchment
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collecting area catches rainfall that runs to a particular stream
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Drainage divides
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drainage basin boundaries coincides w/ ridges separating one catchment from another
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Channel Network
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series of connected streams extending from headwaters to the point of outflow
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hillslopes
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sloping uplands that feed water to channel network
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water in channels
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different characteristics: discharge, velocity, stream incision, overbank flooding
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Discharge
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volume of water moving through a channel at a given place per unit of time-wXdXv cubic meters/sec
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Velocity variation
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depth, gradient
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Depth w/ velocity
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greater depth reduces frinction with banks
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Gradient w/ velocity
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Slope of streambed-decreases downstream, streams cut down towards base level, lower limt of erosion-lowest near ocean
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Stream incision
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deepening of channesl by cutting down into bed-urban streams-deeper due to pavement
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Flood levels
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1.5 years, 50 years, 100 years-statistical probability not exact-go over flood plain
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Zoning laws
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based on 50-100 year flood levels
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erosion and sediment transport
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particle movement, size and rate
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Particle movement
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bedload, suspended load, dissolved load
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Load
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mechanism for transport of sediments
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Bed load
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materials move along bed
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suspended load
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above bed never come into contact w/ bed-cause cloudy water
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dissolve load
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not see-ionic fully dissolved
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Size and rate sediment move
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proportional to flow velocity-silt and fine sand move easiest
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Rivers and Floodplains
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Sinuous/meandering which forms cutbanks and point bars
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Point Bars
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Inside bank of meandering stream higher bank
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Cut bank
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Outside bank of meandering stream-lower bank
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Oxbow
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formed when a meanders join
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Uplands
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above the flood plain
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Natural levee
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deposit sediment forms higher bank
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Braided stream
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multiple interweaving channels-islands of sediment-higher gradient,higher sediment loads, coarse sediments, non-cohesive banks
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Terraces
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Older floodplain surfaces left behind at higher elevations as a river incises downward-caused by cutting down of rivers-paired, unpaired
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Paired terraces
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caused by sudden climate change-tectonic plates
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Unpaired terraces
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gradual river incision-slow changes
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Deltas
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sinking below sea level-sediment dposisits in large water bodies-water move from streams slowed causes coarse sediment to fall out
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General glacier
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occur anywhere there is incomplete melting of snowfall during warm season-as far south as N. Kentucky
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When glaciation
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high altitudes and latitudes
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Ice processes form glaciers
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snow-> high porosity firn->granular spherules glacial ice interlocking ice crystals w/ little pore space
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Firn line
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close to equilibrium line characterized by snow to dark-migrates up glacier during warm season-separates accumlation and ablation zone
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Move mech of glacial ice
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basal sliding, internal deformation
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Basal sliding
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sliding of the glacier over its bed
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internal deformation
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plastic flow-movement of ice via relative move. bt and within ice grains
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Velocity characteristics of glaciers
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velocity faster at the surface until brittle zone-can result in crevasses
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Brittle zone
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upper area won't undergo deformation b/c not enough weight will snap and break
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Crevasses
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breaks in brittle zone-may be snow covered
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Ice Flow and Mass balance
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accumulation, ablation
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Accumulation
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gain of glacial ice via percipitation
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ablation
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loss of glacial ice via melting and sublimination
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net accumulation
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accumulation is greater than ablation results in advance
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net ablation
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accumulation is less than ablatioin results in retreat
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Alpine glaciers
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confined to by valley walls-flow down hill
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Ice Sheets and caps
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not confined to valley walls-cover vallesy and ridge tops
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Ice Sheets
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largest glaciers-cover Greenland-2 miles thick
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Ice Caps
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Mass capping of portions of mtn ranges
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Flows of non-confined
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occurs down the gradient of ice surface from ares of thick to thin ice
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Glacial erosion
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abrasion, striation, plucking
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Abrasion
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drag across rock surface causing glacial polish
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glacial striation
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caused by boulders in glacier gouging in to rock surface
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plucking
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ice flosw oever rocks and freezing drawing rocks out and then taw leaving rock behind
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Glacial landforms
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erosion, deposition
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Erosion
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trough, cirques, aretes, cols, horns, streamlined forms(finger lakes)
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Trough
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ice accumulation in high mtns forms valley glaciers form v cuts out u form melt and forms water falls then tributary valleys
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Tributary valleys
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are hanging valley share a sharp wall-arettes
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Cirque
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bowl shaped depression @ the top of glacial valleys where ice flow starts-alpine
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Horn
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very tall triangual spikes formed by surrounding cirques
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Finger lakes
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formed by galcier carved out running across land-ice sheets
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Glacial deposition
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an ice conveyor belt-drift, till, outwash, erratics-
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Stable glacier
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results in piles of sediement-ablation and accumulation are equal-stagnant-forms end moraine
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Glacial retreat
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Accumulation is greater than ablation-sheets of till-forms a ground moraine
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Glacial advance
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Ablation is greater than accumulation-no apparent moraine
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Glacial till
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unsorted sediment deposits
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Erratic
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unpredictable deposit of sediment-where it couldn't been formed
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Lateral moraine
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is a deposit of till that develops on the sides of valley glacier
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medial moraine
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formed by two lateral moraines
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End moraine
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is a ridge of till found at the terminus of a valley glacier.
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Kettle
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is formed by blocks of ice that are separated from the main glacier - perhaps the ice front stagnated or retreated or perhaps ice blocks were washed out from the glacier during a glacier flood
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Sinkhole
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are common where the rock below the land surface is limestone, carbonate rock, salt beds, or rocks that can naturally be dissolved by ground water circulating through them
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Limestone
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Very easily dissolved w/ water
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River erosion
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creates relief-elevation variation in an area
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Hillside anatomy
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topslope, footslope, toeslope, upper
convexity, lower concavity, talus, scree |
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hillslope denudation
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running
water and mass wasting |
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Mass wasting
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the downslope movement
of rock debris in response to gravity water can be a component |
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Angle of Repose
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the stable angle below which
unconsolidated material will cease to spontaneously slide. (32-35 degrees for loose dry sand) |
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Major Types of wasting
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Creep
Slides Slumps Flows Avalanches |
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Creeps
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mostly in soil; very slow-building problems
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Slides
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(land, rock, mud)
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Slumps
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(coherent); mod.-fast
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Flows
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(mud, earth, debris) High water content; fast
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Avalanches
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(debris, snow) Dry; fast
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