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Surface Processes > River Processes > Flashcards

River Processes Flashcards

1
Q

topographic difference

A

gravity

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2
Q

fluvial transport

A

earth terrestial surface w/ water, not ocean

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3
Q

hydrological Cycle

A 
evaporation
transpiration
precipitation
infiltration
runoff
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4
Q

water exists as

A

liquid water, water vapour and ice (snow)

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5
Q

interphase land and sea

A

only fine grained load deposited

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6
Q

Water as important component and geological agent

A

weathering, erosion + transport, deposition

transfers mass from continents to oceans

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7
Q

Why does it rain in mountains

A

low latitudes: hottest → high evaporation

Approaching air forced to rise, leading to cooling & condensation

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8
Q

Stream Infiltration

A

how streams get started

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9
Q

step 1: Infiltration

A

groundwater
bedrock weathering
soil production

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10
Q

stzep 2: Sheetwash

A

thin layer of water with downslope movement
potential energy kinetic energy
steeper slopes = higher energy
substrate erosion

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11
Q

Step 3: Rills

A

coalesce, deepen, downcut
headward erosion
intense scouring

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12
Q

Stream Gradient

A

stream character & velocity change with distance from origin

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13
Q

most affective reshaping in tererestial environmeent

A

reshaping on terrestial environment: stream gradients control reshaping
bcs they do active transport
important factor: angle

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14
Q

streeam gradient in low latitudes

A

in low latitudes vegetation can hinder streams

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15
Q

the coarser the grain

A

the closer to source, Coarser grains/immature composition typical of steep gradient in headwaters

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16
Q

finer grains

A

further from source, finer grains and more mature composition, Finer grains/mature composition typical of gentle gradients nearer river mouth

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17
Q

clasts weathered during transport

A

mechanical & chemical processes → soft minerals disintegrate or dissolve clay, ions
hard minerals → grain-size diminishes, roundness

18
Q

Sediment Transport

A

high energy environment → large clasts moved
bouncing clasts - erode substrate & weather other grains
flow slackens large clasts dropped, fine grains keep moving

19
Q

a sediments maturity

A

a sediment’s ‘maturity’ is related to length of transport

20
Q

Sediment transport ablauf

A

transport, material in contact with bedrock → contact released while transport → particles kicked up (bouncing) actually make muddy water → suspended load, fine grained material

21
Q

Sediment Transport Factors

A

current velocity, higher with higher gradient
- the more energy the larger grains can be tranported
grain size

22
Q

Sediment maturity refers to

A

mineral composition

grain size & shape ( more rounded the more mature)

23
Q

sediment is composed of weathered grains of pre-existing rocks
large or smaller grains

A

larger clasts - often lithic fragments

smaller clasts – often mineral fragments

24
Q

Mineral composition is diagnostic of

A

sediment source and transport history

25
Q

mineral composition long transport

A

only stable mineral grains

26
Q

mineral composition short transport

A

many unstable mineral grains

27
Q

unstable minerals

A

unstable mafic minerals & feldspars dissolve or chemically alter to stable minerals such as clays and iron oxides

28
Q

breakdwon hastened by

A

mechanical weathering

29
Q

presence of unsatble minerals

A

Presence of unstable minerals = diagnostic of being close to the source (short transport) = immature composition

30
Q

Roundness indicative of

A 
angular = short transport  = immature
rounded = long transport = mature
31
Q

Sorting indicative of

A

well-sorted = uniform energy/long transport (eg beach or dune) – mature
poorly sorted = variable energy/short transport (eg alluvial fan) - immature

32
Q

sediment maturity

A

time and transport sediment evolution from immature to mature

33
Q

textural maturity

A

average grain size (goes down) , roundness & sorting (goes up)

34
Q

compositional maturity

A

unstable minerals (goes down) , stable minerals (goes up)

35
Q

sediment texturally mature

A

can be texturally mature and compositionally immature, and vice versa
maturity is used to reconstruct depositional conditions

36
Q

River Capacity

A

Capacity - amount of sediment carried

37
Q

River Competence

A

Competence - size of clast carried

38
Q

high capacity and high competence

A

high capacity & high competence, eg high velocity, steep gradient: mountain stream → boulders & cobbles moved -

39
Q

high weathering rates

A

high weathering rates
rapid size decrease
rapid rounding increase
small clasts winnowed

40
Q

low capacity and low copmetence

A

abrupt change of gradient: alluvial fan, braided stream → large clasts dropped

41
Q

high capacity and low competence

A

owland meandering stream → wide channel full of water, small grainsize & low energy flow

42
Q

Factors that affect river capacity

A

uplift of mountain

or sea level fall

Surface Processes (14 decks)

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