- Created by: maddyshackley
- Created on: 22-04-16 09:40
what did WM Davis do?
took an evalulionary approach to look at models of landscape evolution over spatial and temporal scales, peaks have decresed through peneplation, now more flat
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what are examples of young, mature and old landforms?
rivers, rocks,lots of steep mountains,mature- flat meandering rivers, oxbox lakes and not much deposition, old-flat, little/no water, dry desert like
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what is peneplanation?
decline in the altitude of the erths surface as it undergoes erosion over time
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what is base level?
equilvent to sea level, level to which the landscape erodes
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what is potential energy?
potential to do work, which is determines by the differnece in height between the base and the peak
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what is renewed uplift?
leads to landscape rejuvination, and a creation of polycyclic landscape (mix of old and young landforms)
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What is climate in relation ot landscape evolution?
landscape evolution is determined by the intensity of geomorphic processes, which varies between humid, arid and glacial environments
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how does geology influence landscape evolution?
lithology and structure influence the evolution of drainage patterns
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What is orographic uplift?
uplift by horizontal compression and folding of the earths crust. subduction of oceanic over continental or two contintal when crust is crumpled, himalays, new zealand
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what is uplift by vertical elevation of large blocks of the earths crust e.g the intrusion of magma into the earths crust called batholites called?
eperirogenic uplift, eg coloardo plateau and deccan plateau
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what % of the height lost due to erosion is regained by isostatic adjustment of the crust?
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what is isostatic recovery?
state of equilibrium between gravity of the earths crust and the mantle, land bounces back up afyer deglacition
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what is denudation?
long term sum of processes that cause the wearing away of the earths surface by moving water, wind, and waves leading to a reduction in the elevation and relief of landscapes
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what is load and what are the components?
load is the total amount of material deposited, dissolved load (20%), suspended oad (70%) and bed load (10%)
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what are the different mechanisms of denudation?
physical, chemical and biological
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what are the four areas deposition can happen in?
at footslope position ice before reaching the rivers:colluvium, , in river flood plains:alluvium, intertidal zones:building up easturaies/deltas, or open sea:alluvial fans
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what is relief?
difference in elevation, between parts of the earths surface, the height of the land, in conjuction with information about the slope and shape is useful
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whatare controls are on denduation rates?
basin relief, climate and vegeation, litholoy, tectonics and storm frequency, river intrusion rate, glaicers, sea level
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how does vegetation have an impact on denudation rates?
more evegetation means less potential for erosion, but when there is too mmuch rainfall, influece of vegetation is 0
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How does lithology, plate tectonics and frequnecy have an effect?
erosion of mountain belts is one of the main sources of material to the river, hgihest erosiion rates are found when there is high denudation, storm frequency, weak substrates conicide
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how does a river incision effect have a role of denudation?
as relief increasesfrom 10-1500m the erosion rate increases, but after this it does not have any effect so climate and tectnoics are the next stages to increase eroison
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how do glaicers have an effect on denudation?
depper valleys and promote uplift, short term erosion can build mountains due to isistatic compensation, but long term it isnt possible
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what controls the heights of mountains?
sum of snowline altitude (depends on climate)and the amplitude of glaical relief(
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where are the highest sedimnet yeilds found globally?
north south america, the andes, highest denudation rates,
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what ios global mean dedunation, surface lowering and isostatic recovery?
global mean - 60/70mmka-1 surfafe lowering, allowing for isostatic recovery - 12-14mmka-1
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what has caused sea level to rise?
euastatic conditions, isostatic adjustmnets and tectonic controls on ocean basin
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what does landscape evolution involve the balance between?
uplif and denudation
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what is isostatic compensation?
flexivity of the lithosphere adjustmnet, increase in topography or presence of low density roots to account for sostaic anomilies
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what is the principle of mass conservation?
mass cannot be created or destroyed
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what is the equation which change in land surface elevation equals?
amount of uplift/subsidence + balance between sediment supply and removal(height change due to erosion)(volume removed/surface area)
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what does qs mean and what is the equation?
qs(in)-qs(out)/river bed area volumetric sediment support
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what is equilibrium?
scale dependent concept where things are in balance
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what is the long term evolution of mountains and the short term evoltion of rivers?
long term- uplift=erosion, short term-sediment in = sediment out
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what was halks concept graphs?
time dependent bs steady state graphs, form decreases over cyclic time, over graded time form flucutates to reach steady state equilbrium abd over steady time reaches static equilbrium, all the same just zoomed in
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WHAT DID GK Gilbert come up with?
concept of mutual adjustment between form and process toward equilbrium, form-distrubtuion-transportof sediment-erosion and deposition
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what did the quantitve revolution leaad too?
greater awareness of process based understanding of landscape and its evolution
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what is the power law?
water flow rate is proportional to sedimnet transport rate, straight line on graphs that have logarithmic graphs, gradient of the line is equal to the power, without log graphs, they are curves
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what are diffusive processes?
sediment movement due to surface gradient, landslides and soil creep
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what are advective processes?
sediment movement by water-driven processes
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what do negative and positive feedbacks generate?
positive feedbacks amplify distrubances, negative feedbacks dampen disturbances
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why do topographic changes during landscape evolution lead to strong negative feedbacks?
qs(sediment transport rate) is proprtional s(slope)
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what does negatuve feedback mean?
that is a river recieved a lot of sediment from a landslide for example then the river would end up in equilbrium in its old form and the system would be balanced and stable
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what is a drainage basin?
area of land that all drains to the same outlet
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what is discharge?
flow rate measured in m3s-(cubic metres per second) amount of water that passes through a given cross section area over certain amount of time
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What is bankful discharge?
discharge that fills a stable alluvial channel up to the elevation of the active floodplain
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what is the equation of discharge?
discharge(Q)=w(width)h(height)V(velocity) or A(area) TIMES V
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what os the equation for velocity?
meausred in metres/second(ms-1) and is dependent on rivers slope, depth and roughness V=C SQUARE ROOT(HS)(h average depth, s=slope, c=roughness)
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What does river capture lead to changes to?
drainage basin area, river discharge, sediment load, greatest impact at the source of a river, as there is headward erosion, joins other tributies and determines what will happen to the river downstream, drainage basin splitting is determined by u&d
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What does the ability to erode and deposit particles depend on?
critical erosion velcoty, which is a log graph, determines when different types of particles sizes erode, deposit and transport in relation to velocity
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what is the transport capacity of a river?
mesaure of the total amount of sediment that it can carry qs=WK)V-Vcr)^2.5 vcr- velocityat which sedimnet is eroded
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what else is transport capacity a measure of?
sheer stress(twith curly bottom) exerted by the fluid and and critical shear stress (curly bottom t cr)instead of velocity
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What is the sediment delivery ratio?
fraction of sedimjet eroded fromslopes that reaches the drainage basin outlet= sediment output from basin/sedimnet eroded from slope
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What is source to sink?
sediment moves from source to sink along a jerky converyer belts and applies at a range of scales, such as asmal scale sediment sotres like at footslopes, storms can have an effect, sand dune is a temporay short term examples, and braided rivers
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what are some long term examples of source to sink?
meanders, deltas, eg indus and bengal fan
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What is accomodation space?
the space available to store sediment which depends on sea level rise(sediment deposited between realtive sea rise), teconic uplift(sediment transported out of eroded headwaters), depends on equilbrium long profile shape of the surface
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what is the long profile?
represents the change in height of the river bed moving downstream from the headwaters to the sea, adjusts to tranport water and sedimnet, concave graph
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what is the lane diagram?
a diagram showing how sediment size and load, erosion, deposition, total water to determine how much sediment is transported are in balance, changes occur in aggregation and degradation
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what are the findings of the lane diagram?
dischrge increases downstream as drainage basin area increases, sediment load increases but at a decling rate because of increased sediment storage, size of sediment decreases due to abrasion, river competence(max size it can transp, sediment sources
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what shape is the lane diagram and what is the equation?
concave, qs is proprtinal is q times s/d s is proprtional to qs/q times d
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what is chanel pattern affected by?
slope+discharge, as channel slope increases, bankfull discharge decreases and bank strength(contorls widening, limit lateral sediment supply, depends on bankmaterial, river load and floodplain construction)
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what is aggradation?
aggradtion- increase in land scape profile due to deposition of sedimnet, deaggradtion-
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what is one of the highest mounatin ranges?
ganges, brahmaputra, once it reaches the river valley, there is loats of deporation so it gets flat, energy drops, alluvial fan
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what is allvusion?
abondement of river channel and formation of new channel during floods
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what is accomodation space available for sedimnet stroage controlled by?
base level, tectonics, equilbrium landform morphology
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what can the equilbrium long profile be explained by?
donwstream changes in water and sediment and the relationship between discharge, grdient, sediment size and the rivers capacity to transport sediment
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what is seal= level change incfluenced by?
eustatic controls, isostaic compression and tectonic adjustmnets
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what is the evolutionary classification model of coastal environments?
over TIME, and after PROGRADATION AND TRANSGRESSION, estuaries move towards deltas types and draw it
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what is transgression?
sea level rise relative to land, moves towards higher ground resulting in flooding and the formation of estuaries
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what is progradation?
growth of a river delta, farther out to sea over time, incoming sediment is greater than the volume of sediment lost through subsidence
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what is morphodynamics?
study of the interaction and adjustment of the sea floor topgaphy and fluid hydrodynamic processes, seaflor morphologies and sequences of dynamics involved in the motion of sediment
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what are examples of sediment budgets?
deltatic coasts, progradation sediment from land estuaire coasts, transgression re infleuce from the sea
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what are the key 5 facts about waves?
generated from seismic activity and wind, deep wave height is determined by wind speed and duration, steepen before breaking, energy is dissipatied provding energy to transport sediment, influeced by fricitonal drag of bed
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what are the 3 main facts about tides?
produced by the attraction of the sun and moon and are influenced by shape and size of ocean basins and coriolis force, iobars=same pressure, water levels can be influenced by storm surges, tides increase
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what is tidal range controlled by?
bathmetry(underwater topography), width of contintal shelf, coastal configuration, distance from amphidromatic point
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what determines the rate of the intertidal zone?
tidal range and coastal erosion, mico4, meso 2-4m, from wave dominated to tidal dominated
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what controls coastal erosion?
wave environment(height, event and frequency), coastal lithology(susceptible to weathering and erosion, strucutre), coastal morphology(platform configuration, cliff height, angle, bathmetry), tidal action, climate, biological actiivty
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what are some of the main erosion landforms?
cliffs(chalk, limestone variety of cohesive materials), shore platforms(energy gets dissipated as it reaches the shore)
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what are depositonal landforms?
long energy systems or high sedimnent input, beaches, barrier islands, estuaries
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what are beaches?
profile/gradient depends on sedimnet size, varies seasonally, pebble more steep, waves dominated in formation of beaches/ars, barriers whcih create barrier islands
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what are barrier islands?
linera, parallel to land and seperated by a lagoon, low gradient coasts with low tidal range
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what are estuaries?
valleys and low land areas drowned by post glacial sea level rise, zone of salt and fresh water mixing, sediment derived from local, fluvvial, coastal sources, depositional controlled by sediment size, water energy and salinity
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what are salt marshes and mud flats?
salt marshes occur on upper parts of the intertidal zone, disected by tidal crees that supply/remove sediment and water, salt tolerate vegetation traps sediment, sensitive to sea level and sedimnet supply
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what controls sediment supply to the coast?
catchment characteristics, climatr, soil and vegetation and human activity in the catchment
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what controls sediment dispersal at the coast?
river flow charactersitcs, river sedimnet load, streth of estuarine tidal currents, streght or absense of offshore currents, buoyancy of river water, wave environemnt
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what are the differnet types of delta?
cuspate(nile, wave dominated), lobate(fluvial, lena), elongate(fluvial, missippissipi), esturaine(tidal, ganges)
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what is long term data accumulation affected by?
delta growth reflects the balance between sedimentation, subsidence, compaction, sediment reworking by waves, tides, currents, sea level change
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what have recent chnages in the delivery if sediment to ocean depends on?
soil erosion, construction of dams
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in the missippissipi what has data sedimentation declined by?what is isostaic subsidence occuring by?
1.7mm/year in 100 years, isostaic 1mm/yr
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what happens as thickness increases?
compaction rate increases
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what are examples of asian deltas?
indus, ganges, brahmaputra, all surrounding the tibetan plateau
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what could be some of the impacts on delta and megacities by 2050?
chanigng sediment input, precipitation change, sea level change, land and shelf subsidence, coastal erosion, subsurface abstraction oil,water,gas, increased population pressure
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what influcnes coastal environments?
water and sediment supply, wave environment and tidal range, ocean basin and coasal configuration, shoreline morphology and lithology, human environment
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how many people living in coastal zones will be at risk from flooding in the future?
half a billion
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What are coastal dunes?
wind brings sand and deposits it in small hills when there is a change in wind spped or it hits an obstancle, rows and right angles to the previaling wind direction
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what controls rainfall?
atmopsheric circulation, continental isolation, rain shadow effect, ocean circulation, aeolian
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what is atmospheric circulation?
tradewinds, coriolis force, jet sreams, ITCZ, hadley, polar, ferrel cells
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what is continental isolation?
more rain around the coast than inland, around 100-200mm, inland but up to 1600mm at the coast
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what is the rain shadow effect?
air rises and warms as it travels over the warm ocean, evaporates and moves over hills due to prevailing winds, as it rises i cools and condendes over the hills which precipitation as rain falls, warms up again, cycle, warm air holds more moisture
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what is ocean circulation?
warm water evaporates and meets cold air which contains less moisture, this mix causes condensation and rainfall, when cold water pass through warm areas you get much less condnsation and drier, nw africa
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what is aeolian?
(greek god of wind), sediment transport, lack of vegetation makes soil vulnerable to erosion of sediment, lack fo moiture leads to an trigger for wind transport as less water means less cohesion
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what is suspension?
dominates in water low, particles are suspended in the water, finest particles carried by turbulent eddies are transported over largest distainces
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what is saltation
dominatates air flow, coarser sand partilces move in long low hops, meaping in air or water
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what is creep?
larger particles slide along surface and are transported in water
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what are desert pavements/regs?
loose particles are blwon away(eroded) from the surface, sediment is sorted by selective entrainment which produces a pavement, erosion is limited by surface coarsening
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what are ventifacts?(priekanters)
produced by abrasion(sand blasting), by wind. changing wind directions and ventifact orientation lead to formation of multiple facets that meet at sharp ridges, one side is abraded and this causes mas balance of rock to change
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what are yardangs?
wind abraded ridges orientated with the prevailing winds and seperated by abraded chutes that conduct wind blown sand
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what are inselbergs?
isolated mountains of resistant rock, rounded slowly by abrasion over long periods of time, more symetrical and are found in low energy environments
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what are sand seas/ergs?
large areas of sand deposition, induced by changes in wind speed(due to barriers or transnitions betwene climate zones), erosion transports sediment when wind is strong but leads to sudden deposiiton as wind drops
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what are dunes?
sand supply, wind regime and vegetation control sand supply, transverse dunes, barchans(cresentic dunes) and longitudunal(seif)dunes, parabolic dunes
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exisiting alone(solitary), cresent shaped dunes whose horns point downwind, form when sand supply is limited and wind is strong and constant
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what are trasverse dunes?
form in rich sand environemtns with storng stead prevailing winds, barchans merge to form long wavy ridges perpendicular to the wind
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what are longitudal(seif) dunes?
long straight ridges more or less parallel to the wind, moderate to low sand supply an storng prevailing winds with minor variations in direction
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What are parabolic dunes?
cresent shaped but tips point upwind, common in coastal areas with modertate to abundant sand and winds and vegetation occur which anchors parts of dunes(the horns) while other parts migrate slip face
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what is te hydrological cycle?
controls the production of run off and the erosion, transport and deposition of sediment, vegetation is ciritcal
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how does vegetation impact the hydrological cycle?
loss of natural vegetation, increased runoff and erosion, soil organic matter decline, soil compaction, downward spiral in soil quality/fertility, soil thickness depends on erosion/weathering. positive feedback with negative impacts
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what are the impacts of deforestation on they hydological cycle?
slope instability, soil erosion, loss of soil productivity, increased river sediment load, destruction of coral reefs, climate impacts, loss of c storage
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what dies vegetation influence?
external (water and sediment supply) and internal processes(bank stregth, island development, roughness, sediment transport, floodplain formation)
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what are ephemeral rivers?
charactersited by flashy flow regimes and unarmoured river beds and high rates of sediment transport during floods, as shear stress increases, sediment transport rate increases only slighly-linear relationship
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what are arroyos?
deep channels found in semi-aris environments, formation driven by land use and climate change(leading to vegetation change), occurence of intense storms and posiitve feedback
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how does vegetation reduce flooding?
vegetation colonises bars that are dry at high flow, prevent significant floodplain flow, slows bank erosion and prevents bend cut off, reduce channel width and force thalweg to link up
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what would be the conditions in a abiotic world?
soils would be shallow/absent, hillslopes would be rocky, rivers would be stepper and rarely meander
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what does anastomosed mean?
connection between two strucutres, vegetation promtes the formation of them and meanders
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what is uniformitarilism?
present is the key to the past- hutton and lyell 18/19th century
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what is gradualism?
earth has envolved slowly over a very long time
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what is catastrophism?
many landforms are a product of extreme events
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big question is is the small/frequent event or large unfrequenct events that odminate landforms?
those that do the most geomorphic work
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what is geomoprhic work?
the total amount of sediment eroded from a hillslope or the total amount transported by a river durying a year
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what does landslide sediment flux equals?
magnitude times frequency, using logs
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what is stream power?
the energy dissipated against the bed and banks of the river/per unit downstream length, greater on bigger irvers on flat terrains which means it can transport more
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what is a loess?
sedimentart deposit composed largely of silt size grains that are loosely cemented by calcium carbonate, usually homogenous and highly porous and its transversed by vertical cappilaries that allows sediment to fracture and form vertical bluffs
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what is avulsion?
rapid abondement of a river channel and formation of a new channel, they occur as a result of channel slopes that are much less steep than the slopes the river could travel if it took a new course, ,water abondens channel, , in braided and meandering
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when does an upper fan surface form?
slope supply>river transport capacity
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whendoes fan entrenchment form?
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what is solar forcing?
change in solar radiation
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what are some climate system feedbacks?
ice albedo, carbon cycle, thermohaline circulation and sea level changes
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where is greatest chages in temperature and rainfall been?
temp- at the poles, rainfall middle of africa
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what is the topography of the earth biomes?
used to be closed forest and then all deserts and now closed forest makes up north and south america, europe, russia and south america and extreme desert in asia and north africa
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describehow post glacial reboud works?
ice sheet on the elastic lithsiphere which is on top of the viscous asthenosphere, elastic l increases in thickness, creates curved bulge, asthen flows out, ice melts quickly and rate is a function of asthenosphere viscosity
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what are u shaped valleys?
erosional landforms by abrasion, ice grinding, carved by glaciers, plucking, erosion/ transportation of rock, crushing, frafturing and meltwater erosion
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what is a hanging valley?
low are between hills, which hangs from source to valley bed
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what is a cirque?
amitheatre shaped valley, which previously would have been the head of a glaicer
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what is an arete
arete, divided between 2 cirques, ridge
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what is a horn?
sharped edge peak formed when 3 peaks come together
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what are stoss and lee forms
up and down glaicer slopes respectively of a rocky obstancle that has been glaicaiated, smooth(stoss) and roughly plucked(lee)
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what is a moraine?
glacial depostis, termainal (furhtest extent), lateral(marks lateral margins of ice), recessional(retreat positions) and push(advancing ice pushes older seposits infornt of it),
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what are drumlins?
small hill, blutnend and tampered end, streamlines landforms that may occur in swarms, higher and wider at glaicial end, fluvial metlwater, glaiceial or flood reposits are formation
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what are kames?
mound like hils of layered sand and gravel, material deposited in an ice supported cavity, ice melts leaving sediment which accumulates in a depression or retreating glacier
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what are eskers?
long sinous ridges of stratified sand and gravel, may be formed by meltwater stream flowing underneath, stagnant glaicer ice, aligned [parallel to ice movement, tens to hundreds of m, glaicer makes contact with bed rock, friction and heat, melt depos
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what are outwash plains?
extensive deposts of fluvial sediment
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what are paraglaical landscapes?
deposited of easily eroded fluvial-glacial deposts and till/drift, disequilbrium between slope erosion and river sediment loads during holocene, modern river loads, primary erosion
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what are entrenched allvial fans?
large areas inwhich a lot of sediment is deposited
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what is landscape evolution?
short term deviations from progressive landscape evolution
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when upland glaicers scour the landscape and suuply abundant materia to rivers where does is it stored?
braidplain deposits and then remobilishesed during intergalcials
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what is remobilisation?
cutting of a trench, sediment cut from the trench is deposited downstreams as a fan, braid plains find river terraces
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what are fluvial knickpoints?
waterfalls and rapids, retrest of this promtosed hillslope erosion
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what are the causes of fan entrechment?
paraglacial decline in sediment supply, product of difference beween slpe and river sediment regimes, process from feedbacks
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what does autogenic behvaiour mean?
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what is equifinality?
when different processes or environemtnal conditions can produce the same landform
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what is climate change going to do to the landscape?
loss of tundra, forests will expand in africa, boreal forests will deceline,rainfall is likely to increase at the poles
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what are the future changes in hydrology in europe
increased flood risk, change in timing of snow melt floods, enhanced soil erosion, potential in north/sotuh europe, sea level ruse 0.5m by 2100, reduced landscape stability
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what is the order of size from lowest to highet of drainage basins in seidment yield?
rhine, missisipi, amazon and jamuna
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Other cards in this set
what are examples of young, mature and old landforms?
rivers, rocks,lots of steep mountains,mature- flat meandering rivers, oxbox lakes and not much deposition, old-flat, little/no water, dry desert like
what is peneplanation?
what is base level?
what is potential energy?