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Ecology 228 > Chapter 5 part 1 > Flashcards

Chapter 5 part 1 Flashcards

1
Q

a) Divergent

A

plates moving apart, new oceanic crust formed @ rift, faulting

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2
Q

b) Convergent

A

: collision of plates, subduction, earthquakes, volcanoes, folding/faulting

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3
Q

c) Transform

A

plates moving past each other, earthquakes

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4
Q

Plate Boundaries

A

a) Mid ocean ridges + Continental Rifts (divergent)
b) Subduction zones, ocean crust dives down more buoyant plate (convergent)
c) Transform, lateral motion and shear

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5
Q

3 Types of Convergent Boundaries

A

a) Ocean subducts under continent (Andes)
b) Ocean subducts under ocean (Philippines, Aleutians)
c) Continent vs Continent, no subduction (Himalayas)

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6
Q
  • Types of faults:4
A

a) Normal:
b) Reverse:
c) Overthrust:
d) Transform:

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7
Q
  • Why does weathering happen
A

 Rocks formed within the crust-high P,T
 Unstable under surface conditions
 Products from weathering=more stable

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8
Q

 Controls on rate of weathering

A

a) Mineralogy
b) Petrology
c) Climate
d) Vegetation

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9
Q
  • Weathering
A

In-situ breakdown and alteration of earth forming materials (physical and chemical)

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10
Q
  • Weathering Front:
A

Interface between weathered material and bedrock

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11
Q
  • Weathering Profile
A

Degree of weathering intensifies as you move closer to surface

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12
Q
  • Soils (weathering)
A

• Most active part of the weathering zone’

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13
Q

Active processes (soil)

A

a) Organic accumulation + decay
b) Oxidation (of Fe + Mn common)
c) Reduction (gleying) of poorly drained soils
d) Ground water movement- moves clays and metal ions down to humid climates ~ evaporation moves salts up
e) Bioturbation-roots, animals + bugs
f) Microbial activity, fungi etc…

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14
Q
  • Soils + Horizons O
A

Organics

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15
Q

Soils + Horizons A

A

Top soil

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16
Q

Soils + Horizons E

A

Zone of eluvation

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17
Q

Soils + Horizons B

A

Zone of illuvation/ accumulation

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18
Q

Soils + Horizons C

A

unlatered-ish parent material

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19
Q

Mechanical breakdown

A

Self explanitory…

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20
Q

 Unloading

A

erosion removes overburden, thus rocks expand + crack

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21
Q

 Thermal expansion

A

heating + cooling, needs frequent extreme fluctuations

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22
Q

 Frost action

A

repeated formation + melting of ice in pores, water expands ~9% upon freezing

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23
Q

 Wetting +drying- swell

A

wet, crack=dry, most effective with clay rich rocks + sediments?

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24
Q

 Salt crystal growth

A

precipitation of salt crystals in rock pores, typical of dry climate + coasts

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25
Q

 Root action

A

plants grow into joints etc… of rocks

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26
Q
  • Chemical Weathering (decomposition)
A

• Secondary minerals (clay) are produced + more prone to dissolution/erosion

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27
Q

Most important agent of weathering

A

water

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28
Q

• Hydrolysis

A

breakdown of water into H+ and OH- ions

a) H ions replace metal cations in rock
b) Accelerated if there’s CO2 in water

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29
Q

• Oxidation:

A

a) Addition of O2 to minerals- forms oxides (rust)
b) Opposite of reduction, available O grabs electron
c) Most effective in aerated presence of air +water

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30
Q

• Solution:

A

a) Dissociation of minerals in water
b) Ions lost to groundwater/surface water-more effective in acidic waters
c) Salts, gypsum, carbonate especially prone to this… No new weathering products

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31
Q

• Carbonation:

A

a) Solution of minerals in carbonic acid (water + CO2)

b) CO2 from atmosphere, decaying organic matter

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32
Q

 Felsenmeer

A

block field topography (Frost Action)=Alpine areas + Arctic/Antarctic

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33
Q

 Karst-formed

A

carbonation (limestone)=humid climate

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34
Q

• 3 phases to sediment movement

A

a) Erosion
b) Transport
c) Depostion

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35
Q

• Sedimentary processes

A

requires weathering, sediment=fragments of rock that have moved from their original position

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36
Q

• Slopes may be:

A

a) Weathering limited
b) Erosion limited or
c) Equilibrium

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37
Q

Typical forms of slope

A

a) Convex upper slope (erosional)
b) Straight mid slope ( transport)
c) Concave lower slope ( depositional

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38
Q

Management implications (slope)

A

a) Erosion may increase with more surface runoff=weaker slope
b) Possible causes: Land clearing, roads, farm equipment, ranging livestock
a) Erosion may increase with more surface runoff=weaker slope
b) Possible causes: Land clearing, roads, farm equipment, ranging livestock

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39
Q
  • Mass Wasting
A

Spontaneous downslope movement of soil or rock material primarily under the influence of gravity (water’s important for this role)

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40
Q

Erosional Mass Wasting landforms

A

cliffs, scarps and gullies

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41
Q

Depositional Mass Wasting landforms

A

various types of debris blocks, piles, lobes, cones etc

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42
Q
  • Colluvium:
A

sediment deposited by mass wasting + other hill slope processes

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43
Q
  • Colluvium:Properties
A
  • Unsorted
  • Low-moderate compaction
  • Often angular(source material?)
  • Un-stratified or weakly stratified
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44
Q

Mass Wasting occurs when

A

driving forces > resisting force

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45
Q

a Driving force

A

downslope component of weight (shear stress) [mgsinβ]

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46
Q

b) Resisting force

A

(shear strength) (S) with components; [ mgcosβ

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47
Q

c) Friction (angle of internal friction/response)… has to do with (mass Wasting)

A

texture, angularity and compaction

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48
Q

e) Water content

A

pore pressure

49
Q

f) Factor of Safety

A

used to assess slope stability. If

1) Fs>1 stable slope
2) Fs,1 unstable slope

50
Q

Thus stable slopes eventually fail because

A

rain/snowmelt, over-steeping, loading, earthquakes or just weathering

51
Q

Creep Def:

A

1) Slow, shallow downslope movement of soil or sediment.

52
Q

Creep Main mechanisms

A

a) Freezing/thawing

b) Wetting/drying

53
Q

Creep indicators

A

: uphill-bent trees, tilted poles, folded strata, small terraces

54
Q

Slides Def:

A

sliding of masses of rocks and or sediments with variable speeds

55
Q

Characteristic of slides

A

a) Failure with a distinct plane
b) Usually a pre-existing weakness
c) Opening for water, thus less friction
d) Translational or rotational
e) Slumps-deep seated rotation with minimal downslope movement (Dallas rd)

56
Q

Debris Avalanches

A

sliding material often disintegrates, fast, and referred to snow/ice

57
Q

Flow

A

Movement of liquefied material with debris forming a lobe.

58
Q

Flow Occurs when

A

a) Large amounts of weathered material available
b) Lots of water
c) Steep slopes

59
Q

Mud flow

A

Rapid, mostly fine sediments and water that’s common with steep, arid regions ~ Lahars with volcanoes

60
Q

• Earth Flow

A

slow to moderately rapid movement with saturated soils/sediments and are common with marine clays

61
Q

• Debris flow

A

Rapid, muddy water with course material (trees, boulders, dead animals etc..) and are common in BC mts that deposit poorly sorted material

62
Q

Falls

A

Free fall of soils or rock (very steep slopes) form talus(scree) @ base of cliffs

63
Q

Types of mass wasting

A

Creep
slides
Debris Avalanches
Flow-mud,earth, debris

64
Q
  • Streams/rivers
A

channelized flow/runoff

65
Q

Functions of streams

A

 Sediment dynamics create channel form
 Important for fish habitat, engineering, water supply, irrigation etc…
 Drainage networks/watersheds (Horton system of stream ordering)

66
Q

Flow amounts

A

Most important variable
• Discharge (Q=wdv)
• Related to climate +position in watershed
• Determines channel size/style

67
Q
  • Flood prediction
A

 Magnitude-frequency analysis

68
Q

Bad flood prediction because

A

problems are that records are short, spread out and often heterogeneous

69
Q

• Sedimentary processes Streams (erosion)

A

1) Erosion of material that was removed from bedding or banks with erosional landforms such as cutbanks, thalwags, scour, pools and canyons.

70
Q

• Sedimentary processes Streams (Transport)

A

2) Transport meaning either, suspended in water column or dissolved

71
Q

• Sedimentary processes Streams (Deposition)

A

3) Deposition when water slows down… sediment texture reflects flow velocity with depositional landforms such as: bars, floodplains etc..

72
Q
  • Determinants of Channel form (variables)
A

Discharge (Q), sediment load (Qs) Texture (D) and slope (S) ~ sinuosity

73
Q

 Small Channels:

A

a) Low stream order/discharge
b) Usually steep=high velocity
c) Usually course bedding material
d) Width>depth
e) Common patterns: step-pool(steepest) or Cascade-pool. Both have low sinuosity + low sediment transport

74
Q

 Intermediate Channels

A

a) Higher order/discharge
b) Moderately steep slope
c) Width»depth with large woody debris + stones
d) Riffle pool channel most common (low sinuosity, sediment transport)

75
Q

 Large Channels

A

a) Higher discharge
b) Wider valleys/floodplains
c) Slope usually < 1°
d) W»>D

76
Q

• Straight (channel)

A

low sinuosity with a single channel a) Uncommon in large rivers, usually steep slopes (small stream) or geologic control (large) with Pool/riffle sequences

77
Q

• Braided (channel)

A

low sinuosity with multi channels c) Multi small shallow and low-sinuosity channels with many bars and usually unstable with floodplain less distinct. Typical of an erratic discharge regime and a relatively steep slope with course bedding material( >sand) and has a large sediment load

78
Q

• Meandering

A

b) Regular cutbank/point bar/pool/riffle sequences and a distinct floodplain. Typical with regular discharge regime and sediment texture (sand-fine gravel)

79
Q

• Anastamosing

A

d) Intermediate or between braided and meandering that forms multi, stable and low sinuosity channels with well-developed levees and many vegetated islands. Floodplain is clearly distinct with typical regular or predictable flow regime with a low-moderate slope.

80
Q

• Wandering

A

e) Transitional between braided and meandering with 1 main channel and 2 secondary channels having a gravel bed and an occasional, stable, vegetated islands.

81
Q
  • Depositional Zone
A

All rivers end somewhere and when they do… sediments are dropped (in oceans, lakes or larger rivers) that create these forms;

82
Q

 Alluvial fans

A

Sloping fan shaped deposits in larger valleys. Vary from gravity flowed (colluvial fans ~ poorly sorted with steep gradient) to fluvial flow (fluvial fans with braided stream sands or gravel and a relatively low gradient)

83
Q

 Deltas

A

when a river enters lake or ocean. They are flatter and finer grained then alluvial fans with their shape dependant on coastal processes (tides, waves

84
Q

 Channel Gradation

A

has an exact slope needed to move its sediment load given its discharge regime ~ Aggradation=excessive deposition of sediment or degradation=excessive erosion of the river bed

85
Q

 Fluvial Sediments (alluvium):

A

happen on bars and floodplain that have diverse properties that depend on the depositional situation… properties of channel sediments: well rounded, well sorted, clast-supported, non-compacted and rich in sedimentary structures(cross bedding) whereas the properties of a floodplain sediments are usually: silty and fine sands, organics with horizontal bedding.

86
Q

• Implications for stream ecosystems could be: (Dam Building)

A

1) Habitat loss, fragmentation or degradation
2) Water quality changes (temp, O2, Nutrients)
3) Invasive species no colonizing
4) Riparian succession

87
Q

Primary changes to a river (Dam building)

A

: Flow magnitude and timing, sediment supply or cut off by the reservoir whereas,

88
Q

Secondary changes (Dam building)

A

above… becomes a lake and below the dam… degradation or aggradation, bedding material changes, and channel size +pattern changes

89
Q

 River regime

A

seasonal variability in the water balance with 4 main river regimes;

90
Q

4 Main river regimes

A

1) Snow/ice melt
2) Temperate Oceanic environments
3) Tropical, non- equatorial river system
4) Equatorial

91
Q

Highest erosion Conditions-

A

sparse vegetation or heavy rainfall, sediment yield/unit area is highest for small rivers and Calibre of sediments vary

92
Q

Sediment affected by anthropogenic

A

poor agricultural practises, construction and deforestation

93
Q

 Dominant Discharge concept

A

rivers erode and receive sediment input during flood events, of which the flood with the most geomorphological work

94
Q

 Dominant Discharge concept a) Large floods

A

most potential to erode + transport

95
Q

 Dominant Discharge concept medium floods

A

occur more frequently (most influential)

96
Q

 Dominant Discharge concept small floods

A

cannot mobilize course fragments

97
Q

Perturbation

A

caused by tributary inputs and bank collapse

98
Q
  • Channel bed morphology
A

 Downstream fining of bed material particle size and rounding.

99
Q

 Erosion + depositional bedforms include

A

pool-riffle sequences, Dunes and anti-dunes, Bars(variability in grain size) etc…

100
Q
  • Littoral Zone:
A

interface between land and water body. It extends inland usually several km’s from the point of wave break to backshore

101
Q

Coastal Landscapes

A

all coasts feature either a combination of erosional and depositional processes/landforms.

102
Q
  • Erosional features can be classed 3 ways;
A

a) Headlands + bays
b) Caves, arches and stacks
c) Cliffs +wave-cut platforms

103
Q
  • Depositional landforms
A

a) Beaches, spits, bay barriers, tombolos, lagoons, dunes, deltas

104
Q
  • Waves
A

• Friction of wind on water creates waves… energy source for most coastal geomorph processes

105
Q

Wave energy

A

a) E depends on, wind strength + duration and fetch

106
Q

b) Wave modification

A

refraction ~ conforms to bottom topography ad becomes almost parallel to shoreline

107
Q

Wave refraction results in:

A

Energy is concentrated on headlands( Erosional), Diffused in bays ( depositional- beaches)
Promotes Coastal Straightening over time.

108
Q

Wave induced currents Result

A

Sediment zigzags along coast in multiple jumps

109
Q

Wave induced currents Shore-normal

A

Swash and back wash- Undertow, rip currents

110
Q

Wave induced currents (longshore or littoral)

A

Direction depends on incoming waves

111
Q

Swash zone Processes (longshore)

A

Uprush (swash) Water sinks and backwashes and lifts sediments back obliquely into swash zone= Net result= beach drift

112
Q

Beaches are

A

depositional
Energy Dissipaters
Highly Transient

113
Q

Components of t beach

A 
Step 
bar 
berm 
beach face 
low tide terrace
114
Q

Beach profile

A

Shape and steepness related to wave conditions

115
Q

Steep vs gentle profiles

A

Steep is reflects, gentle dissipates

116
Q

Swells vs Storm waves

A

(summer vs winter)

117
Q

Storm beaches

A

Storm surge : high winds pile water up

Builds abnormally high beaches

118
Q

beach sediment properties

A

Highly sorted: Fine particles washed away

119
Q

Texture of beach sediments

A

is proportionate to wave energy

Ecology 228 (4 decks)

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