Term
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Definition
- straight
- meandering
- braided
- anastomosing
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Term
3 ways to transport material in a river |
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Definition
- dissolved load
- suspended load
- bedload (saltate or roll/creep)
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Term
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Definition
1. gradient (vertical distance/horizontal distance)
2. bank stability (vegetation, sediments, etc.)
3. bedload (how much sediment you have within the flow) |
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Term
What affects the velocity of a river? |
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Definition
1. river gradient
2. friction (slows it down)
3. amount of water entering the system (# of tributaries)
4. discarge (amount of water passing over a specific point at a specific time (volume/time)) |
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Term
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Definition
1. low flow: water is confined to channel and is well below the banks
2. high flow/bedload: water in channel but banks are full
3. overbank/flood: water escapes banks, spills onto the surrounding area (flood plain) |
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Term
What do younger rivers do? |
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Definition
1. downcut
2. headwater erosion |
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Term
What do mature/older rivers do? |
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Definition
1. move over landscape rather than through
2. have a graded profile (lateral) |
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Term
3 things to know aobut V-shaped rivers |
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Definition
1. really narrow
2. high velocity
3. found closer to mountains |
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Term
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Definition
the "curviness" of a river
actual path or channel length/ shortest path or down valley length |
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Term
What is fluvial capacity? |
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Definition
ability of channel flow to carry sediments aside from bedload |
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Term
What's the difference between braided and anastomosing rivers? |
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Definition
1. braided rivers have easily erodable banks while anastomosing rivers have cohesive banks that don't tend to move as much
2. the width to depth ration of anastomosing is less than braided
3. anastomosing's main movement is veritcal while braided's main movement is lateral |
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Term
Where do you find braided rivers? |
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Definition
upper reaches of a system where there is intense erosion/ near source/ well above graded profile/ alluvial fans or glacial outwash |
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Term
What kind of sediments are found in braided rivers? |
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Definition
coarse to fine sands; trough x-beds, tabular x-beds, rippled sands; sand and silt overbank |
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Term
Describe the sinuosity of a braided river. |
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Definition
it has low sinuosity overall but individual channels can have high sinuosity |
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Term
Describe the discharge of a braided river. |
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Definition
discharge is low with high sediment load |
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Term
Describe the gradient of a braided river. |
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Definition
high gradient to low gradient transition (steep to less steep/level) |
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Term
Where are the coarser sdiemtns in a braided system found? |
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Definition
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Term
How are bars in a braided system formed? |
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Definition
by impediment to flow... a large object |
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Term
3 kinds of bars found in braided systems |
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Definition
1. longitudinal bars
2. traverse bars
3. cross channel bars |
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Term
Tell me about longitudinal bars. |
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Definition
1. They aggrade (the level rises by deposition) and migrate downstream.
2. they are found more often in upper reaches where there are coarse sediments and pebbles
3. strat: planar at the bottom, x-beds, finer sands in between from channel
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Term
Tell me about Traverse bars. |
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Definition
1. they are broad and lobate
2. made up of finer sediments b/c they are found in the lower reaches
3. during floods you get mega-ripples
4. structures: ripples, dunes, trough cross beds
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Term
Tell me about Cross Channel bars. |
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Definition
1. are found where smaller channels enter larger channels
2. flow is more lateral or oblique
3. x-beds show flow perpendicular to main flow
4. strat: trough x-beds, scouring, coarse sed (channel base), fine sed (bar top), abrupt FU sequence, wide stacked lobes |
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Term
sinuosity of meandering river? |
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Definition
super sinuous (channel length high compared to distance) |
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Term
Gradient of meandering river? |
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Definition
low gradient (slower flow, caries suspended sed relative to bedload) |
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Term
velocity of meadering river? |
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Definition
velocity varies
1. high velocity = erosion = outer bend
2. low velocity = deposition = inner bend |
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Term
Tell me about the feautres of a meandering river. |
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Definition
1. point bar: where the velocity is low and sediment is deposited
2. cut bank: where the velocity is high and the land is eroded
3. oxbow lake: the really sinuous part of the river gets cut off
4. meander scar: a dried up oxbow lake
5. neck: the part that cuts off the oxbow lake
6. crevasse splays: rising water causes levee to be breached and water spills out onto floodplain
7. avulsian: breached side of channel where new sinous course starts on flood plain |
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Term
sinuosity of straight rivers. |
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Definition
the name gives it away duhhh
it's straight and has LOW sinuosity |
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Term
gradient of a straight river? |
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Definition
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Term
fWhere are straight rivers found? |
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Definition
at headwater where energy is very high
also found in areas where flow path may be controlled by underlying geology |
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Term
Are straight rivers popular? |
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Definition
NO. no ones likes them.
jk. they're rare |
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Term
sinuosity of anastomosing rivers? |
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Definition
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Term
anastomosing systems are made up of.. |
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Definition
a trunk (the main channel) and anabranches (smaller channels) |
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Term
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Definition
flowing water (high energy) meets standing water (low energy) |
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Term
How does the sed supply compare to erosion in a delta? |
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Definition
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Term
What are the parts of a delta? |
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Definition
1. the upper and lower delta plain
2. the delta front/slope
3. the prodelta (submarine shelf) |
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Term
When does a delta have an elongated shape? |
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Definition
high supply and hyperpycnal (river water is more dense than receiving water body) |
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Term
When is the delta shape more like a lobe? |
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Definition
moderate supply + homopycnal (desnities are the same) |
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Term
Where are glaciers found? |
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Definition
at high latitudes and altitudes where it snows more than it melts |
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Term
How much of the earth do glaciers cover? |
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Definition
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Term
Glaciers are good agents of... |
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Definition
transport and erosion (wind and water don't even compare!) |
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Term
What was a major time of glaciation? |
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Definition
carboniferous age and 7 million years ago during snowball earth |
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Term
Erosion from glaciers causes a lot of... |
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Definition
scouring which crates U-shaped valleys |
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Term
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Definition
bowl shaped depression where erosion from glaciers start |
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Term
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Definition
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Term
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Definition
a sharp ridge formation that is created when glaciers on both sdies of the mountain slide down. |
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Term
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Definition
a pointy mountain looking thing that is created from glaciers eroding |
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Term
deposits and sorting from glaciers? |
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Definition
all grain sizes from boulders to clay that are poorly sorted |
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Term
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Definition
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Term
Glacials are either advancing or retreating. What does this mean? |
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Definition
It's either boldozing forward or melting and ropping what its carrying |
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Term
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Definition
ridges or mounds where it tells where snount is melting; |
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Term
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Definition
one ridge or mound behind the other as glacier retreats |
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Term
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Definition
where two glaciers ran into each other |
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Term
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Definition
unsorted glacial sediment deposited at terminal moraine |
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Term
When do glacial lakes form? |
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Definition
When streams get blocked and a dam forms |
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Term
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Definition
the pattern of light dark sediments that get layered from glacial lakes that freeze and thaw ever winter and summer |
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Term
What happens when glacial lakes thaw? |
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Definition
lake becomes lighter because oxygen is introduced and the lake is oxidized |
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Term
What happens when glacial lakes freeze? |
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Definition
they become darker because reduction occurs from organics |
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Term
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Definition
wind blown glacial flour (silt and clay); the areas where the flour setlles become fertile farmland |
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Term
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Definition
furthest point that glacier got to |
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Term
4 parts to depositional history |
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Definition
1. sediment provenance/source
2. transport direction
3. geometry
4. chronology |
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Term
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Definition
1. accomodation space
2. tectonics and sedimentation
3. climate
4. organics |
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Term
Tell me about sediment provenance/source |
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Definition
provides the weathered products/sediments
source tells you the mineral type |
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Term
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Definition
1. size of the sediment is related to energy
2. roundness related to distance
3. imbricated to paleoflow direction
4. structures related to paleoflow direction and type
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Term
Geometry- what kind of units and formations can we see in cross sections? |
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Definition
pinch out, thickness, facies, unconformity, biological changes |
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Term
What controls sediment preservation? |
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Definition
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Term
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Definition
flow is usually perpendicular to basin margin |
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Term
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Definition
the trunk challen flows axial while the feeder system flows perpendicular |
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Term
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Definition
because of drop in sea level |
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Term
Changes/succession in facies indicate.. |
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Definition
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