River Processes

Question 1

topographic difference

Answer 1

gravity

Question 2

fluvial transport

Answer 2

earth terrestial surface w/ water, not ocean

Question 3

hydrological Cycle

Answer 3

evaporation
transpiration
precipitation
infiltration
runoff

Question 4

water exists as

Answer 4

liquid water, water vapour and ice (snow)

Question 5

interphase land and sea

Answer 5

only fine grained load deposited

Question 6

Water as important component and geological agent

Answer 6

weathering, erosion + transport, deposition

transfers mass from continents to oceans

Question 7

Why does it rain in mountains

Answer 7

low latitudes: hottest → high evaporation

Approaching air forced to rise, leading to cooling & condensation

Question 8

Stream Infiltration

Answer 8

how streams get started

Question 9

step 1: Infiltration

Answer 9

groundwater
bedrock weathering
soil production

Question 10

stzep 2: Sheetwash

Answer 10

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

Question 11

Step 3: Rills

Answer 11

coalesce, deepen, downcut
headward erosion
intense scouring

Question 12

Stream Gradient

Answer 12

stream character & velocity change with distance from origin

Question 13

most affective reshaping in tererestial environmeent

Answer 13

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

Question 14

streeam gradient in low latitudes

Answer 14

in low latitudes vegetation can hinder streams

Question 15

the coarser the grain

Answer 15

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

Question 16

finer grains

Answer 16

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

Question 17

clasts weathered during transport

Answer 17

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

Question 18

Sediment Transport

Answer 18

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

Question 19

a sediments maturity

Answer 19

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

Question 20

Sediment transport ablauf

Answer 20

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

Question 21

Sediment Transport Factors

Answer 21

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

Question 22

Sediment maturity refers to

Answer 22

mineral composition

grain size & shape ( more rounded the more mature)

Question 23

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

Answer 23

larger clasts - often lithic fragments

smaller clasts – often mineral fragments

Question 24

Mineral composition is diagnostic of

Answer 24

sediment source and transport history

Question 25

mineral composition long transport

Answer 25

only stable mineral grains

Question 26

mineral composition short transport

Answer 26

many unstable mineral grains

Question 27

unstable minerals

Answer 27

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

Question 28

breakdwon hastened by

Answer 28

mechanical weathering

Question 29

presence of unsatble minerals

Answer 29

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

Question 30

Roundness indicative of

Answer 30

``` angular = short transport = immature rounded = long transport = mature ```

Question 31

Sorting indicative of

Answer 31

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

Question 32

sediment maturity

Answer 32

time and transport sediment evolution from immature to mature

Question 33

textural maturity

Answer 33

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

Question 34

compositional maturity

Answer 34

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

Question 35

sediment texturally mature

Answer 35

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

Question 36

River Capacity

Answer 36

Capacity - amount of sediment carried

Question 37

River Competence

Answer 37

Competence - size of clast carried

Question 38

high capacity and high competence

Answer 38

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

Question 39

high weathering rates

Answer 39

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

Question 40

low capacity and low copmetence

Answer 40

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

Question 41

high capacity and low competence

Answer 41

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

Question 42

Factors that affect river capacity

Answer 42

uplift of mountain | or sea level fall