geomorphology Flashcards
(70 cards)
1
Q
why is earth considered a ‘goldilocks planet’
A
- not too hot or cold
- water can be in all 3 states
2
Q
exogenic processes
A
- external to earth
- driven by sun/solar radiation
3
Q
endogenic processes
A
- internal to earth
- thermally driven (nuclear reactions)
4
Q
sedimentary cycle
A
- continental crust forms, exposed to atmosphere, becomes unstable, weathering/erosion occurs, debris created, transported, deposited
5
Q
igneous cycle
A
- rock solidifies from molten state, turned into magma
- magma is high pressure high temperature and can be objected into a solid
- it is then either intrusive or extrusive
6
Q
if magma cools beneath rock…
A
intrusive
7
Q
if magma breaks outside of rock and cools…
A
extrusive
8
Q
main plate tecontic points
A
- 7 major plates
- plates are mobile
- thermally-driven
- gravitiationally-driven
- proof in large scale topography
9
Q
7 major plates are…
A
- pacific
- indo-australian
- north american
- south american
- african
- eruasian
- antarctic
10
Q
plates move __ per year
A
7cm
11
Q
ridge push
A
plates spread with gravity, move from high to low
12
Q
slab pull
A
leading descending edge pulls rest of plate down. disconnects from other plate and forms a trench
13
Q
mountains occur when…
A
2 plates collide and converge
14
Q
mid oceanic ridges occur when…
A
plates are divergent
15
Q
trenches occur when…
A
one plate subducts beneath another
16
Q
subduction zone
A
when one plate goes under another
17
Q
divergent boundary
A
plates moving apart
18
Q
convergent boundary
A
plates moving together
19
Q
transform boundary
A
plates sliding past
20
Q
movement in southern alps
A
avg 40mm transform, 22mm convergence per year
21
Q
alpine fault links…
A
2 subduction zones
- to north, south plate subducted
- to south, indo-aus plate subducted
22
Q
orogenesis
A
mountain building processes
23
Q
high mountains means…
A
high rates of erosion
24
Q
steep slopes means…
A
unstable
25
deep gorges means...
high sediment loads
26
interaction of endo/exo results in...
- slope processes
- fluvial processes
- glacial processes
27
weathering is...
physical and chemical alteration of rock at the earths surface
28
once rock is exposed to atmosphere...
unstable and break down
29
physical weathering includes what processes?
- freeze-thaw activity
- crystal growth
- hydration
- pressure release
30
freeze-thaw activity
- physical weathering process
- liquid to solid phase change
31
crystal growth
- physical weathering process
- crystal grows inside rocks and displaces volume
32
hydration
- physical weathering process
- material swells up with water
33
pressure release
- physical weathering process
- rock relaxes at greater volume and may break
34
what is physical weathering?
physical breakdown of rock
35
what is chemical weathering?
- decomposition of minerals in rocks
- driven by reactions in air, water and minerals
36
regolith
product left behind after weathering
37
what are slopes responsible for?
- mass movement/wasting
- graviational movements of debris
38
driving forces on a slope
- gravity
- weight
- size
- shape
- moisture
- slope angle
39
resisting forces on a slope
- friction
- cohesion
- frictional strength
40
coulomb equation
shear stregnth equation
shear strength = cohesion + effective normal stress x coefficient of plane sliding friction
41
fall
- material airborne at some stage
eg rockfall
42
avalanche
- material falling and tumbling
- material partly airborne
eg snow, debris
43
landslide
- cohesive/semi-cohesive material
- moisture plays role
44
creep
- slow movement
45
flow
- high moisture content
- turbulent
- high sudden moisture supply
46
how people impact slopes to make them unstable
- deforestation
- overgrazing
- drainage
- earthworks
47
how is sediment/particles transported
- gravitational processes - eg slopes
- fluids - water, ice, wind/air
48
hjulstrom curve
shows particles eroded, transported and deposited
49
what is described on the left of the hjulstrom curve
cohesion
50
what is described on the right of the hjulstrom curve
mass effect
51
erosion on slopes is defined by the balance between...
erodability of rock/soil and erosive power of water
52
driving forces of stream flow
gravity
53
resisting forces of stream flow
- friction
- channel boundary
- sediment tranport
54
how does velocity of a stream work
- friction at bed slows water
- air friction at top of river also slows water
- as you move away from bed and air, there is less friction, so velocity increases
55
entrainment occurs when...
bed shear stress exceeds friction of material on bed
56
channel DEGREDATION in alluvial channels
stream power > sediment supply
57
channel AGGRADATION in alluvial channels
stream power < sediment supply
58
processes of erosion in rock channels
- abrasion
- plucking
- cavitation
59
how does abrasion work in rock channels
scraping/wearing away
60
how does plucking work in rock channels
pulling material off bed
61
channelization definition
all processes of river engineering for purposes of flood control/protection
62
types of channelization
- re-sectioning
- realignment
- diversions
- embankments
63
how does re-sectioning work in a channel
- increase width or depth
- increases cross-sectional area
- increases channel capacity
64
how does realignment work in a channel
- straightening channel by making cuts
- increases gradient velocity
- decreases flood levels
65
how do diversions work in a channel
alteration of natural course
66
how do embankments work in channel
- banks built adjacent to river channel
- confines floodwaters
67
what makes a positive mass balance in a glacier
inputs
- snow
- rainfall
- avalanching
68
what makes a negative mass balance in a glacier
outputs (erosion)
- melt - surface, basal, englacial
- sublimation
- calving
- avalcnhing
- deflation
69
what happens at accumulative zone of a glacier
ice formation in a glacier
70
what happens at ablation zone in a glacier
ice loss in a glacier
