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DAY 1: FINAL EXAM > River Series 3 > Flashcards

River Series 3 Flashcards

1
Q

In topographically low parts of the landscape ______, ________, and _________ sediments are deposited

A

valleys, pidemonts, coastal plains

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2
Q

Fluvial sediments are laid down, and depositional landforms are created at:

A
  • Dominantly or partially subaerial conditions
  • Topographic discontinuities
  • Valleys and the margin of water bodies
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3
Q

Restricted lateral movement and confined within the valley

A

upstream channel

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4
Q

Channels are able to shift positions over wide areas

A

Near baselevel

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5
Q

Arid to Semi-Arid Environments
Large Sediment Supply
Occurs in Fault fronts, Tectonic Mountain Fronts or Sudden Topographic Discontinuities
General gradient: 3-6°
Marginal screes: ~30°
Near the apex: ~10°

A

Alluvial Fans

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6
Q

Upper part is incised passing outward to braided streams. Generally poorly sorted sediments near the head due to torrential deposition. It becomes better sorted sediments outwards with finer grains

A

Fan structure

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7
Q

Conglomerates/unsorted sediments near the head, with bettering sorting and finer-ing of sediments outwards.

A

Sediment mechanics of alluvial fans

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8
Q

Exhibits complex cross-bedding and Flow Structures

A

Bedding

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9
Q

an size should be related to the size of the sediment source area AKA drainage basin.

A

Growth of fans

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10
Q

Have a smaller fan, compared to fans underlain by mudstone and shale

A

Geology influences the relation, in a drainage basin e.g underlain by sandstone

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11
Q

Fan surface is not dissected. Relatively smaller than fans of perennial streams

A

Dry fans

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12
Q

Streams flows through incision. Coarser materials are rarely carried downstream. River widens downstream, braided. Progressively shifting channel

A

Wet fans

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13
Q

Where alluvial fans are large enough, or sufficiently closely spaced, they may coalesce laterally to produce a depositional bed. To produce a __________.

A

Peidmont zone or Bajada

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14
Q

Mainly are terraces and floodplains of a river. Normally finer upward. Channels are mainly braided to meandering though some other rivers

A

Valley fills

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15
Q

Change in positive baselevel change: resulting into the backfilling of the
Uplift or Change in climate: resulting into increased sedimentation, sediment load progressively moves down the system
Uniform filling of the valley: increase in production of sediments from the numerous tributaries

A

Valley Filling

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16
Q

Enumerate the channel types in valley fills

A

Meandering
Anastomosing
Braided
Straight

17
Q

Sinuous Channels
Near Baselevel
Low Gradient/Flat
Fine Sediments (Mainly suspended loads and dissolved loads)
Shifts laterally

A

Meandering channels

18
Q

Low Bedload discharge
Low sinuousity
Low bedload unless due to incision

A

Straight

19
Q

Relatively permanent
Cohesive banks, Sinuous channels
Diverges/Converges around stable, vegetated bars

A

Anastomosing stream

20
Q

High sediment supply
High Gradient changes
Low stability

A

Braided

21
Q

Enumerate the causes of braiding

A

Overloading of sediments discharge

Steep slopes which produce a wide shallow channel where bars and islands form readily

Easily erodible banks which permit widening at high flow

Large bed material load, in comparison with its suspended load where large material is immobile except during high flood stages

22
Q

Alluvial surface adjacent to a channel that is frequently inundated. Highest elevations normally occurs on the abandoned levee and point bar ridges

A

Floodplains

23
Q

Occasionally be formed by the incision of bedrock surfaces, but they are most likely the remnants of floodplains trenched by rivers. Caused by negative baselevel changes- resulting into headward surges of rejuvination

A

River terraces

24
Q

______ may represent reworking and may contain heavy mineral concentrations

A

Terrace sediments

25
Q

Formed when sediment-laden rivers flow into standing bodies of water.

A

Deltas

26
Q

Geomorphic Characteristics of deltas are determined by the following factors:

A

Relative densities of the river water and standing water

River hydrology and variations of discharge
The amount and caliber of river load esp. bed load and suspended load

Intensity of coastal processes, particularly: wave action, longshore currents and tidal scour

Geometry of the slope

Vertical tectonic stability

Climate

27
Q

The dynamics of the delta morphology is strongly influenced by the relative densities of the inflowing and standing waters

A

Delta morphology

28
Q

Carries large proportions of fine suspended load
Usually occurs to the snout of tide water glacier
Submarine slumps produce turbidity currents: Graded beddings

A

Hyperpycnal

29
Q

Typically is when rivers flow into freshwater lakes.
Devoid of significant tidal or wave forces
Bedload settles immediately

A

Homopycnal

30
Q

Rivers flow into saltwater (most common)
Coarse bedload is deposited near the mouth as leeves
Fine suspended load carried seaward in the surface which spreads over the sea
Produces gently sloping submarine delta front

A

Hypopycnal

31
Q

Floodplain sands and silts; marsh organic deposits; platform sands.

A

Topset

32
Q

Cross-bedded coarser sands and silts of the delta slope, together with channel fingers- grading laterally into clay and marsh deposits and sand splays

A

Foreset

33
Q

Offshore clays, toeslope turbidity silt deposits

A

Bottomset

34
Q

Deltas are dominated by the removal of river debris by wave or tidal currents
Wave Influenced/Dominated
Tide Influenced/Dominated

A

High destructive

35
Q

Deltas are dominated by large debris supply from the river
Lobate/Fan
Elongate/Bird’s foot

A

High constructive

36
Q

Flattened in a pan
Rapid removal of debris by strong longshore currents

A

Wave dominated

37
Q

Funnel Shaped distributaries
Open and straight distributaries

A

Tide dominated

38
Q

Much of the debris is coarse
Distributaries change in position similar to alluvial fans
Compact distributaries

A

Lobate fans

39
Q

Delivers large quantity of fine sediment
Builds out
Constantly shifting

A

Elongate/ Birds foot delta

DAY 1: FINAL EXAM (6 decks)

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