Geomorphology 2Nd Year

Front 1

L2: Earth System Science

Back 1

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Front 2

Define earth system science:

Back 2

-Earth is a system and interactions occur between atmosphere, hydrosphere, lithosphee, biosphere, and heliosphere (space-sun to outerplanets)

-Exogenic.

Front 3

Define a system? Give example

Back 3

-Linked/chain events lead to outcome.

ie: Fluvial systems: Variables define alluvial channel form and processes:

channel: Run H20 -discharge/volume
Slopes: Steep:increase velocity (gravity and vegetation decrease velocity

Front 4

How does carbon chain have feedbacks within all parts atmosphere? What is a complexity that can change levels carbon in air?

Back 4

a) Anthrosphere: Breathe air-plants decrease CO2
b) Biosphere: Herbivores eat plants/ eaten by carnivores
c) Hydrosphere: Organic waste in oceans
d) Lithosphere: Dead remains

Volcanic eruptions- cause cooling for climate change- chuck out idea occurring.

Front 5

What is the purpose of models used in geomorphology and give some examples?

Back 5

-Order/ break down systems to parts
-Represent for learning

A) Shape-morphological models
B) Process (glacial) and response (movement) models

Front 6

Define what atmosphere is and composition of it?

Back 6

-Gasoues sphere that envelopes the earth-gases:
N, O, CO2, H20 vapour, emissions etc

Front 7

Give different layers of atmosphere and earth?

Back 7

1) Anthrosphere: Air breathe- we leave imprint on it- human made buildings etc

2) Heliosphere: Space between sun and other planets

3) Cryosphere:
Earth surface - solid H20-ice and snow

4) Biosphere:
Life zone-humans and organisms

5) Lithosphere:
Solid earth crust- above/below sea- continental and oceanic- interior layers

6) Hydrosphere: H20
71% of earth
97% saline
3% fresh:
-77% polar ice sheets/glaciers (slow move H20)
-22% ground H20
-1% Lakes (fast move H20)

Front 8

Why is earth considered an oblate spheroid (not circular)?

Back 8

Polar radius < equatorial radius

Front 9

What is a geoid and how is it similar to equipotential surface idea?

Back 9

Geoid: Represents mean sea level: oceans/imaginary canals on surface continent. Allows oscillations (tides)

Equipotential surface: Allows surface irregularities (bulge/depression). Ultimate base: continental erosion:

Source= eorsion-continents, ocean basin deposits=sink

Front 10

What is global hypsometry?

Back 10

Distribution of heights above/below sea level ( trenches)
-Frequency distribution
-Bimodal (above/below)
-Continental platforms/ ocean basins (71% earth)

Front 11

What are some major morphological features?

Back 11

a) Orogenic moutnain belts- Andes
b) Rift valleys (pull apart volcanoes near Africa)
c) Continental shelf (New Guinea)
d) Continental slope
e) Mid Ocean ridge
f) Trench (Chile)-6000m deep
g) Island Arc: Indonesia-volcano chain

Front 12

What is isostasy?

Back 12

State of balance of the earths crust-lighter continental masses float denser substratum-buoyancy.

Front 13

What are 2 theories on why issostasy occurs and give 2 examples of where it occurs on earth?

Back 13

Pratt model: Part crust stands higher because lower density
Airy model: Part crust stands higher as lower density and increasing thickness.

eg: Mountains after mountain building:
-Erode (unloads weight-uplift)
-Sediment to oceans
-Overall balances: bulge in ocean instead


Icebergs:
Ice uplifted as ice has 0.1 lower density than water.

Front 14

What is importance of plate tectonics?>

Back 14

Most recent theory unifying nature earths crust.

Front 15

What did Wegener find out?

Back 15

Fit, rock type/climate, palaeontology

Front 16

What is palaeomagnetic evidence for plate tectonics>?

Back 16

Remanent magnetism
-Apparent polar wandering

Front 17

What is evidence of Gondwana breakup?

Back 17

Plate tectonics, continental geography, fossils.

Front 18

What is the plate tectonic theory/model?

Back 18

-7 major paltes: Antractica, North and South America, Pacific, Indo-Aussie, African, Eurasian

-Plates move relative to eachother and earths axis (70 mm per year)

Front 19

What are different plate boundary types?

Back 19

Divergent, destructive, collision, transform= exert influence on geomorphology expressed.

Front 20

L3: Geomorphology of plate margins:

Back 20

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Front 21

What is the significance of plate tectonics and give examples?

Back 21

Significance: Form landscapes
eg: Sthern Alps: Plates slide (mtns interact with ciruclation system-Westerly)- orographic rainfall=14000mm/yr rain, very fast change landscape- erosion 10x normal rate.

Front 22

What are the 2 types (with parts) of mrchanisms of plate motion?

Back 22

-Shallow convection/upper/ whole convection (Thermal)

-Ridge push, slab pull , gravity sliding ( mechanical)

Hence: Thermal mechanical process.

Front 23

What are the 3 different types/ conditiosn and associated features for plate boundary interactions?

Back 23

a) Divergent:
-Spreading margins
-Tensional (pull and rip) stresses dominate
eg: Sea floor spread/rift-volcanoes (lava moves away from pull apart area)

b) Convergent:
-Compressional stresses (push together-crumple)
-Subduction
-Collision orogens


c) Transform
-Shear stresses (edges slide- strike-slip)
-Compression too/convergence (oblique slip margins)-transform margins

Front 24

What are the different types for convergent plate interaction?

Back 24

a) Oceanic-oceanic
b) Oceanic-continental
c) Continental-continental

Front 25

Explain what occurs at an intercontinental boundary (continent-continent)?

Back 25

-Passive continental margin ( transition between oceanic / continental not active plate margin)
Evolves to:
-Active margin
-Suture zone (subducting)-2 continents weld

eg: Himilayas

Front 26

What occurs intra -oceanic island arc (oceanic-oceanic)?

Back 26

-Subducting oceanic plate-trench
-Heat of plate: rising magma (igneous intrusions/eruptions)
-Morphologically distinct: fore/volcanic/back arcs
eg: Western Pacific (Solomon and Bismark arcs)

Front 27

What occurs at continental margin orogen ( oceanic- continental)?

Back 27

-Subduction oceanic below override continental
-Frictional heating-rise magma plume (increase orogenic belt)
-Granite intrusions

eg: Olympic Mountains

Front 28

Describe features of the Andes mountain range?

Back 28

-9000km long, >5000m high
-Granite intrusions
-Substantial uplift (>900 volcanoes)
-Melting (subduction zone)

Front 29

What is the Southern Alps an example of and describe some key stats on the movement of the plate/plate arrangements in area?

Back 29

-Transform fault:

Average motion= 40mm/yr transform, 22mm convergence (dominant is vertial uplift)

Alpine fault- 2 subduction zones
a) North= Pacific plate subducted
b) South=Indo Aussy.

Front 30

Lecture 4: The Geomorphologists toolbox

Back 30

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Front 31

Define geomorphology?

Back 31

Transdisciplinary

Front 32

What are 2 views of what geomorphology is, give examples?

Back 32

a) What geomorphologists do:
-Dictated by past practice looking at ecogenic structures on earth-processes related
-Scale determined by problem to solve

b) Field survey: Map landforms ( always better resolution)
-Data resources: Topography, aerial photos, satellite remote sensing.


eg:
-Mt Taranaki: Radial draiange patterm-increase density and contour shade with higher altitude
-Spot: colour attributed to wavelength
-Infrared
-Geological/geomorphic maps combined
-Major landforms , colour for age of landforms combined.

Front 33

What is Lidar and some applications for each version?

Back 33

LIDAR=Light + radar
-Measure distance (pt target)
-Scan (analyse reflected light)
-Illuminate targets

2 main applications:
a) Ground (terrestrial scanner)=
-Photo over groun taken geomorphological model-picks 10mm change in cliff
-safety in mines (volume removed and bulges
--Glaciers :calving events

b) Airborne ( overland- move side to side aeroplane)
-Impact active tectonis on land:GPS strike slip fault-river movement
-West coast: costly to filter topography with trees out of it
-Apline fault details

Front 34

What is GPR?

Back 34

Ground Penetrating Radar:

-Small, remote sensing
-Use: Over 2 beach ridge crests=also take care make more accurate.
-Core taken be more accurate.

Front 35

What are the two ways to date events and landforms on earth?

Back 35

a) Relative dating: Sequence landforms/ events (comparison)
b) Numerical dating: Numerical age -land/events= Geochronology ( Earth age model)

Front 36

Describe the use of radiocarbon dating?

Back 36

14C
-Plants create 14C via photosynthesis
-Things eat plants- die and decay
-Concentration of Carbon with 1/2 life of carbon known when decaying to 14/7 N, can see age.

Front 37

What are some problems with radiocarbon dating?

Back 37

a) Radiocarbon concentration atmosphere varies in time
B0 Different parts biosphere/ hydrosphere different cycling times ( beside river inject C)

Front 38

What is exposure age dating/

Back 38

-Cosmic rays hit rocks- produce rare and measurable nuclides (concentration tells age)
-Use of low concentration determination measurer

Time: Few 100 to 100,000 years.

Front 39

What is an example of meauring process rates/

Back 39

-Sediment rating curves ( discharge record: record sediment transport/ erosion)
-Regression equation: Qs (discharge sediment)- a (constant) x Qb(power)

Front 40

What are problems with sediment rating curves?

Back 40

-Sediemnt generation doesnt equal sediemnt yield.

Generation=rate sediemtn forms/erodes
Yield= rate sediement exported-different storage/reycling
-Bed load-10% in N.Z.

Front 41

Measuring process rates-what does this involve?

Back 41

-Erosion rates longer time scales (10^6-10^8 yrs)
-Thermochronometry
-Measure erosion/uplift: millions to 10's millions yrs
-Time/temp histories- rocks (argon/Helim fission)- start minerals cool below closure temp
-Combine with known thermal gradient earth- long term erosion

Problem: Substantial uncertainties.

Front 42

L7: Mass Movement 1:

Back 42

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Front 43

What are the uses of a hydrograph?

Back 43

-Basic analysis stream flow: discharge vs time

Front 44

What are chemo and sedigraphs?

Back 44

-Chemograph: anticlockwise hysteresis: concentration ions/chems water is biggest at 1st stage-1st injected into system as old

Sedigraph: Most at start-deposit of sediment built up-gets less. (clockwise hysteresis)

Front 45

What are 3 different runoff types?

Back 45

a) hortonian overland flow
b) Saturated zone overland flow
c) Subsurface storm flow

Front 46

What are the 4 diffusive (gravity driven) slope processes?

Back 46

a) Slope erosion: material erodibility vs erosive pwoer: transprot rate proportional t slope
eg: Ross creep-vege help stabilitse and decrease effect steep slope

b) Raindrops: Break down soil, splashes break down, turbulence sheet flow

c) Sheetwash: Roll ground (traction

d) Soil creep: Increase down slope movement (freeze-thaw)

ALL= POTENTIAL TO KINETIC ENERGY
Weathered materials off slope

Front 47

What are 2 forms of water flow landscape formations?

Back 47

1) Rills:
-Conc sheet wash
-Depth for turbulence
-Entrain larger particles
-<0.5m

Gullies: >0.5m (size distinguished)
-Unconsolidated seidment

Front 48

What is the difference between diffusive and advective processes/ what do they both contribute to?

Back 48

Diffusive: gravity driven/slope angle

Advective: Water flow driven/ dependent discharge /slope

Front 49

What are 3 constituents of shear strength?

Back 49

a) Friction: angle:max angle different for cohesiveness particles
b) Effective normal stress (90 degrees plane slide-pores included with upward pressure)
c) Cohesive forces: electromechanical-binding

Front 50

What is the coulomb shear strength equation?

Back 50

s (Shear strength)= σ' (effective normal stress) x tan(φ)-coefficient plane sliding friction

With cohesion included:

S=c+σ'.tan(φ)

Front 51

What is the shear stress equation?

Back 51

T (shear stress)= ps (soil density) x g(gravitational accleration) x zs(soil thickness) x sinѲ (slope angle)

Constants: gravity, slope, soil thickness, so overall shear stress generally constant over time.

Front 52

What is the factor of safety, and what does it tell us?

Back 52

F=Σ R (resist force) / ΣD (driving force)

F=1 (equilibrium)
F<1 (failur slope
F>1 ( stability)

Front 53

What are the uses for factor of safety/what does it consider?

Back 53

-Summarises controls of slope stability:

a) Material properties (density H20/soil, cohesion, angle friction)
b) Geomorphic characteristics ( soil depth/slope)
c) Time variant conditions: (proportion soil thickness saturated and pore H20 pressure)
d) gravitational acceleration.

Front 54

What are the five main parts of the infinite slope model?

Back 54

1) Resisting shear strength
2) Pore pressure upwards from soil
3) Driving shear stress
4) Effective normal stress downwards
5) Slope angle of failure plane.

Front 55

What is infinite slope model usually used for?

Back 55

- Analyze stability of slopes to shallow, planar landslides.
-Balance: shear strength-slope materials, shear stress-gravity- downslope orientated component of mass of soil.
-Considers pore pressure /slope effect.

Front 56

L8: Mass Movement #2:

Back 56

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Front 57

What are the different components of slopes- regoliths on them with water?

i
f
p
b

Back 57

i=rain intensity
f=infiltration rate
p=percolation rate
b=breadth across slope

Front 58

How do we calculate volume of regolith and give example of how to calculate remaining available capacity?

Back 58

Volume regolith=2bh
Porosity (n): capacity hold H20=n (2hb)

ie: Assume n=0.5 z=0.6 Block capacity therefore =0.3 m^3

Field capacity at start (20% pore space filled with H20)- capacity inflitrate new H20= (0.8) x (0.3)=0.24m (left over to be filled)

-Antecedent moisture can play large role

Front 59

What are the 3 types of mass movement?

Back 59

a) Type of movement (rock fall vs slide)
b) Velocity (fast: creep vs rock avalanche)
c) Water content

Front 60

What are 3 types of mass movement?

Back 60

a) Pure flow: Different rate displacement across structure
b) Pure slide: Equal rate displacement
c_ Pure heave: Ice/H20 expand and contract

Front 61

What are the 5 different parts of Varnes'(1975) classification?

Back 61

1) Fall: Steep faces-airborne
2) Topple
3) Slides (failure well defined shear plane, translational/rotational
4) lateral spread
5) Flow (shear throughout moving mass)

Front 62

What are 2 types of materials/forms on slope?

Back 62

1) colluvium: Unconsolidated material slopes
2) Tallus (scree): Particles bottom cliff physical weathering.

Front 63

What degree/where is soil cover on following slopes?:
Convex, concave, straight, compound?

Back 63

Convex: top (diffusive weathering dominated gravity)
Concave: Hydraulic processes: advective H20
Straight: Mass movement dominated (also H20)

Compound: Mixture of all.

Front 64

What is the impact of resistant rock on slope profile?

Back 64

-Rock strength controls output of slope, not processes as usual
-Strength equilibrium slopes: units with characteristic angles
-Structural slopes: Controlled rock structure

Front 65

What are the two main slope type forms?

Back 65

a) Weathering limited slopes: Weathering rate< transport capacity, no/thin regolith
b) Transport limited slopes: Weathering> transport (thick regolith).

Front 66

What is the interaction between slopes and fluvial system?

Back 66

-Hydro transfers
-Material (sediment) transfers

1) Rcok weathering
2) Slope processes=mass wasting
3) iver transported debris.

Front 67

L9: Fluvial Processes # 1:

Back 67

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Front 68

What are the 2 opposing flows within water?

Back 68

Gravity (accelerate and channel slope)

vs

Resisting (frictional) forces

Front 69

What are the 4 main different flow characteristics?

Back 69

a) uniform/ non-uniform flow: Constant velocity in space/ varies in space: velocity gets greater closer to middle vs velocity swayed to one side on corner.

b) Steady/unsteady flow: Velocity constant in time (linear relationship) vs varies in time (unsteady oscillating trend)

c) Laminar/turbulent flow: Laminar=each element moves specifc path with uniform velocity-no real mix. shear stress distributed. Turbulent: shear stress mixed.

d) Tranquil /rapid flow: (Critical/subcritical flow)-determines flow natue and forming bedforms channel floor.

Front 70

How do you work out laminar vs turbulent flow?

Back 70

Work out using Reynolds eqn:

Re (Reynolds #)= v (flo velocity) x R (Hydraulic radius or H20 depth)/ V (Kinematic viscosity)

Re<500=laminar
500<Re<2500= Transitional flow
Re>2500=turbulent flow

Front 71

how do we work out if critical or subcritical flow?

Back 71

use Froude # eqn:
F (Froude #)= v (flow velocity)/ SQRT g( Acceleration) x d (depth flow)

F<1= subcritical/tranquil
F>1=supercritical/rapid
F=1: Flow critical.

Front 72

What is the difference between hydraulic jumps and drops?

Back 72

Hydraulic jump:
-Go from supercritical to subcritical
-No change discharge/v
-Rapid, shallow to deeper, slower= slower H20 (decelerates)

Hydraulic drop:
Subcritical to supercritical
-Acceleration

Front 73

What is flow velocity influenced by and how does it vary within channel?

Back 73

Influenced by: Gradient, roughness, channel cross-sectional area.

Velocity-channels varies 4 directions:
-With depth
-Downstream
-Across stream
-With time

Front 74

What is flow resistance?

Back 74

-Water: deformation fluid resistance (viscosity-molcule movement)
-3% energy H20 left after friction for sediment transport
-Change viscosity with change sediment conc.

Front 75

What are the 3 different equations used to measure flow resisitance?

Back 75

Chezys equation:
C (Chezy coefficient)= v (mean flow v) x SQRT R(hydraulic radius) x s 9Channel gradient)

Mannings equation:

v(mean flow velocity)= R (hydraulic radius)^0.66 x s (channel gradient)^0.5 / n Mannings roughness eqn -usually betweeen 0.02 and 0.06)

Controls for mannings dependent river- organic matter, banks, boulders etc.

Darcy-Weisbach eqn:

ff( Darcy-Weisbach roughness coefficicent)= 8g (gravity acceleration) x R( hydraulic radius) x s(Channel gradient)/ v(mean flow velocity)^2

Front 76

How do we work out hydraulic radius (R)?

Back 76

R -Cross sectional depth/wetted perimeter

Front 77

What are the different resistance variables in flow carrying sediemnt?

Back 77

-Grain/ surface rougness
-Form roughness
-Channel irregularirites
-Suspended materials in flow

Front 78

What are the 3 important stream energy constituents?

Back 78

a) potential energy: PE=m (mass) x g (gravity accleeration) x h (height above base level)

b) Kinetic energy: KE =0.5 m (mass) x v^2 (velocity)

c) thermal energy.