Geomorphology Flashcards
1
Q
The largest component of earths materials
A
Rock
2
Q
Earths circumference and radius
A
Circumference = 40,000 km
Radius = 6,371mm
3
Q
Planets with high mass and low density (Jovian)
A
Outer, cooler planets
4
Q
Planets with low mass and high density (terrestrial)
A
Inner, hotter planets
5
Q
Earths compositional layers
A
- Core: high density metallic
- Mantle: high density rock
- Crust: low density rock
6
Q
Layering based on physical properties
A
Inner core: solid
Outer core: molten
Mesosphere: hot, strong
Asthenosphere: hot, plastic
Lithosphere: cool, rigid
7
Q
Exogenic energy/heat flow
A
Solar radiation
8
Q
Endogenic energy/heat flow
A
Nuclear reactions within the earth
9
Q
The outcomes of energy and heat flow within the earth (thermogenesis)
A
- Convection currents
- Changes in solid/liquid/gas phases of rock
- Creation of magma
10
Q
The rock cycle is a _____ material system
A
Closed
11
Q
Dual drivers of rock cycle
A
- Endogenic processes
- Exogenic processes
12
Q
Crust is made up of how many major plates
A
Seven
13
Q
What drives the motion of plate tectonics
A
- Thermally driven heat from the core
- Gravitationally driven
14
Q
Founder of the theory of tectonic plates
A
Alfred Wegener
15
Q
The most recent and most sucessful concept that uniies ideas about the nature of the earths crust
A
Theory of plate tectonics
16
Q
Evidence of tectonic plate motion
A
- Landmasses fitting like a jigsaw puzzle
- Fossil patterns across continents
17
Q
What does thermally driven plate tectonics entitle
A
- Partial melting under pressure (10% liquid)
- Convection currents in the mantle
- Coupling/decoupling at the 50-100km depth (Litho-Asthenosphere boundary)
18
Q
Results of gravitationally driven tectonic plates
A
- Ridge-push
- Slab-pull
19
Q
Large scale topographic evidence of plate tectonic motion
A
- Mountains
- Mid oceanic ridges
- Trenches
20
Q
Basic large-scale processes of plate tectonic motion
A
- Rifting
- Sea-floor spreading
- Subduction
- island arcs
- Continental collision
- Orogenesis
21
Q
Three types of plate boundary
A
- Divergent
- Convergent (destructive, collision)
- Transform
22
Q
Forms of convergent plate margins
A
- Steady state
- Collision
- Oceanic-oceanic crust
- Oceanic-continental crust
- Continental-continental
crust
23
Q
What happens at a oceanic-continental plate boundaries
A
- Subduction of oceanic plate bneath a continental plate
- Frictional heating leads to a rising magma plume
- Granite intrusions are emplaced within the mountain mass and volcanic activity develops
24
Q
What happens at transform margins
A
Relative plates sliding past each other can grip and create oblique-slip margins causing earthquakes.
25
The alpine fault and its two subduction zones
The pacific plate is subducted in the north
The Indo-Australian plate is subducted in the south
26
What visible features occur at
1. Continental-continental margins
2. Oceanic-oceanic margins
3. Oceanic-continental margins
1. Suture zones exhibited, where one continental margin subducts below the other and form a mountain range with an extensive upland plateau on one side and a longitudinal river system parralel to the range on te other side
2. Oceanic plate subducts below another oceanic plate creating a volcanic arc and an adjacent deep sea trench
3. Oceanic plate subducts below continental plate resulting in terrestrial volcanic arcs and a deep trench just offshore.
27
Collisional plate boundaries result in
1. Orogenesis
- high rates of crustal deformation
- high rates of incision
- steep slopes and frequent landslides
- very high rates of landscape change
28
Southern alps average motion
40mm of transform motion per year
22mm of convergence per year
29
Southern alps rising rates
11mm uplift per year
11mm erosion per year
30
Outcomes of mountain ranges on subduction zones
1. Uplift
2. Thickenening
3. Increased relief
- Steeper slopes
- Decreased slope stability
4. Development of faults
- Decrease in strength
31
Endogenic-exogenic interactions
1. Slope processes
2. Fluvial processes
3. Glacial processes
4. Coastal processes
32
Evolution of ocean basins key dates
Break up of Pangaea 225 mya
Continental seperation 180 mya
33
What has caused the pacific to shrink
Formation of the Atlantic from the seperation of America and Africa
Atlantic growth +160%
Pacific growth -35%
34
Ocean basin architecture
1. Ridges
2. Abyssal planes
3. Seamounts
4. Continental shelves
5. Trenches
35
Oceanic ridges
Symmetrical ridge and trough structures 100-1000 km wide, produced by sea floor spreading
36
Abyssal plains
4000-6000m deep flat plains between ridges, trenches or continental shelves that are made up of cool older ocean crust
37
Seamounts
Submarine mountains that were former volcanos that can break the surface and develop reefs
38
Continental shelves
Shallow areas beyond continental margins covered in terrigenous sediment that are most affected by sea level changes
39
Trenches
Created at subduction zones where the oceanic plate subducts under another plate
40
Sea level fluctuations
1. Short term
- tides and waves
- minutes-years
2. Intermediate term
- eustatic changes
- Isostatic changes
- 10-100,000 years
3. Long term
- tectonic changes
- 1-100 ma
41
Eustatic sea level changes
Global, immediate, ocean volume changes which can be steric or coupled
42
Steric eustatic changes
Density changes (temperature and salinity), loss in density equals loss in sea level
43
Coupled changes
Water storage changes (glacial and interglacial periods)
44
Isostatic sea level changes
Results from isostasy:
- gravitational equillibrium
- bouyancy
- thin, low density crust "floats" on high density crust
45
Loading and unloading of the crust
1. Removal and addition of rock mass (erosion/deposition)
2. Removal and addition of water/ice (ice sheet growth/decay)
46
Is fresh or salt water more dense and basic than the other
Salt water
47
Denudation methods
1. Wearing away the land surface
- surface lowering
- weathering, mass movement, erosion, transportation
2. Potentential energy
- uplift
3. Kinetic energy
- solar powered
- water movement
48
Denudation
The process of the earths surface being eroded
49
Weathering
1. Physical and chemical alteration of rock at the earths surface
2. A passive process distinguished from the dynamic role of fluids, wind and ice
3. An equillibrium process
- rocks formed in one environment moved to another
- instability
- reduced to more stable forms
4. Does not involve transportation of materials
50
Physical weathering
Physical break up of rocks caused by a variety of processes which generate stresses within or upon rock masses
51
Types of physical weathering
1. Freeze-thaw activity
2. Crystal growth
3. Hydration
4. Pressure release
52
Chemical weathering
Decomposition of minerals in rocks with reactions between air, water and minerals
53
Regolith
Residual materials that have resisted weathering (soil)
54
Types of chemical weathering
1. Hydrolosis - breakdown of silicate minerals
2. Oxidation - reaction of O2 forming oxides (rusting)
3. Carbonation - water reacts with c02 forming weak carbonic acid
4. Solution - water dissolving a mineral
55
Karst landscapes
Landscapes particularily susceptible to chemical weathering
56
Karst landscape requirements
1. CaCo3 rich limestone
2. Joint patterns to allow water penetration
3. Aerated zone between ground and water table
4. Vegetation cover
57
Factors controlling the amount of dissolved Co2
1. Concentration of Co2 in the air
2. Temperature (cooler water absorbs more Co2 than warmer water)
3. Biological processes (decaying humus source of Co2)
58
Three components of shear strength
1. Friction characteristic (angle of friction)
2. Effective normal stress
3. Cohesive forces
59
Coulumb-Terzaghi shear strength equation
Shear strength = Cohesion + effective normal stress x tan angle of friction
60
Driving and resisting forces
Driving: gravity acting on slope materials
- weight
- size, shape
- moisture
- slope angle
Resisting: friction
- cohesion
- frictional strength (weight component)
61
Slope instability is
Episodic (progressive)
62
Types of mass movementa
1. Fall - material airbourne
2. Avalanche - snow/debris is falling/tumbling
3. Landslides - cohesive materials planar or curved to slope
4. Flow - high moisture content
5. Creep - slow, expansion
63
Cohesive materials
Materials stuck together ie soil
64
Anhropogenic effects on slope unstability
Deforestation, overgrazing, drainage, earthworks
65
Sedimentary part of the rock cycle driven by
Exogenic processes (weathering, erosion, depositon)
66
Clastic sediments
Composed of particles (clasts) from:
1. Pre existing rocks
2. Weathered products of igneous, metamorphic and sedimentary rocks
3. Weathered products transported away by running water, wind or ice
67
Sediment characterization
Size, shape, variability, colour, lithology
68
Grain size techniques
Φ scale, sieves, settling tubes, laser
69
Statistical description of grain size
1. Mean
2. Sorting (standard deviation)
3. Skewness of distribution
4. Kurotosis (peakedness)
70
Sorting statistical description
Coarse, poorly sorted, subangular
71
What does shape and size of grains tell us
1. More rounded = more abrasion
2. Smaller = more communition over time
3. Better sorting = viscosity of fluid
72
Diagram that explains transportation in water
Hjulstrom curve
73
Higher water velocities =
Larger particles
74
Sediment transport in water requires energy that
1. Can initiate transportation
2. Can maintain transportation
3. Allows deposition
75
Biological sediments
Composed of animal and plant remains
76
Carbonate sediments
Made of CaCO3 such as limestone
77
Terrestrial sediments
Peats, (plant matter, moss) coal
78
Chemical sediments
Minerals precipitated from lake or sea water
79
Chemical sediments from least soluble to most soluble
Calcite - CaCO3
Gypsum - CaSO4
Halite - NaCl
80
Cave precipitites
Speleotherms
- stalagmites, stalactites, travertine (flowstone)
81
Types of sedimentary environments
- Continental
- Coastal and marine
82
Stream flow characteristics
1. Driving forces and resisting forces
2. Material characteristics
3. Velocity
4. Discharge
83
Stream flow driving force and resistence
Driving force: gravity
Resistence: friction and sediment transport, channel boundary, water/particle
84
Discharge continuity equation
Discharge = flow width x flow depth x mean flow velocity
Q = w.d.v
85
Stream power (potential to do work) equation
Stream power = density of water x acceleration due to gravity x discharge x channel gradient
Ω = p.g.Q.S
86
Types of sediment transport depending on stream velocity and sediment characteristics
1. Solution
2. Suspension
3. Saltation
4. Traction
87
Bed rock channels
Erosion of the channel boundary
88
Channel boundary erosion processes
Abrasion, Plucking, Cavitation
89
Direct sediment into bed rock channels supplied by
Slope processes into streams
90
Alluvial channels
Unconsolidated fluvial channel systems
91
Stream power > sediment supply =
Stream power < sediment supply =
Channel degradation
Channel aggradation
92
Channel degradation and aggradation
Degradation is the lowering of a stream channel caused by increase in stream power carrying sediments away
Aggradation is the deposition of material in the stream
93
How are sediments in alluvial channels transported
Bed and suspended load dominated
94
Alluvial fans
Fan shaped accumulations of stream deposit
95
Meandering streams result when
Sinuosity > 1.5
Sinuosity = channel length/valley length
96
Flood plain morphology
Levees, oxbow lakes, crevasse splays, abandoned channels
97
Braided streams
Channel multiplicity that is formed ans dissected by bars
98
Braided stream characteristics
- high width/depth ratio
- high slope
- high sediment load
- bed load dominated
99
Recorders of environmental change
Terraces through their, precipitation, vegetation, hydrology, sediment supply.
100
Why do people modify river channels
For flood control, drainage improvement and reduction of bank erosion.
101
Types of channelization
1. Re-sectioning - increase width/depth to increase channel capacity
2. Reallignment - Straightening channels to increase gradient velocity
3. Diversions - alteration of natural course
102
How do lined channels help channel velocity
Low roughness = less resistence = high velocity channels
103
Primary source of coastal energy
Waves
104
Components of a wave
Height, length, steepness, period
105
Mass sediment transport in the surf zone
- Swash and backwash
- Littoral currents
- Rip currents
106
Storm surges result in
High tide, low atmospheric pressure, landward mass transport
107
Forms of tidal coasts
Microtidal - wave dominant
Mesotidal - wave and tide co dominant
Macrotidal - tidal dominant
108
Products of deposition at deltas
- Aggradation
- Progradation (extension of deltas)
109
Hard coasts
Unprotected by barriers and has direct wave attack, creating seaside cliffs, arches and stacks
110
Glacier types
Valley glaciers, ice sheets, ice shelves
111
Cold vs warm vs thermally complex glaciers
Cold - frozen at bed
Warm - water at bed
Thermally complex = bed partially frozen
112
Glacier mass balance/ inputs and outputs
Inputs:
Snow, rainfall, avalanching, regelation ice
Outputs:
Surface melt, basal and englacial melt, sublimation, deflation, calving, avalanching
113
Glaciers can be split into two sections
Accumulation zone and Ablation zone with equillibrium line to sperate them
114
How does the equillibrium line move in glaciers
1. Positive mass balance = glacier thickens/advances and Equillibrium line moves down the glacier
2. Negative mass balance = glacier thins/retreats and Equillibrium line moves up the glacier
115
Ice flow three componenets
Internal deformation, Sliding, Subglacial sediment deformation
116
Equation for general glacial flow
Glens flow law
117
Glens flow law equation
Strain rate = constant for ice hardness x shear stress^empirical exponent
118
Basal shear stress equation
Shear stress = ice density x gravitational acceleration x ice thickness x sin glacier surface slope
119
Glacial internal deformation
Occurs in all glaciers where frozen bed 'creeps' down the valley
120
Glacial sliding
Water acts as lubricant at glacier bed and slides glacier down valley
121
Subglacial sediment deformation
Mobile or deforming bed moves glacier down valley
122
Where is material transported through glaciers
1. Supraglacial (on top)
2. Englacial (internal, streams)
3. Subglacial (bed erosion)
123
Glacial depositional processes
Active deposition (lodgement)
Passive deposition (melt out, flow)
Both result in poor sorting with wide range of particle sizes
124
Outcomes of milankovitch cycles
1. Seasonal assymytries in annual radiation reciept, creating a variable pattern of solar radiation distribution
2. Radiation reciept in low latitudes mainly affeced by eccentricity and procession
3. In high latitudes, radiatio reciept is mainly affected by tilt
