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Geo 101 > Coastal > Flashcards

Coastal Flashcards

(64 cards)

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1
Q

Neap Tide

A

Less tidal range than Spring Tide
& 1/2 and 22 day marks
Sun and moon are in quadrature (90 degrees out of phase)

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2
Q

Spring tide

A

Larger tidal range than Neap tides (lower low and higher high tides)
1 and 15 day marks
Occurs when sun and moon are in conjunction or opposition

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3
Q

Diurnal Inequality

A

Two high tides and two low tides of unequal sizes in the same day
Measured in difference of height between two successive low or high tides

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4
Q

Apogee

A

When the moon is furthest from the earth

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5
Q

Perigee

A

When the moon is closest to the Earth

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6
Q

Tidal Range

A

The vertical distance between the high tide and the succeeding low tide.

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7
Q

Wave Base

A

equals half the wave length.
wave motion affects water particles up to this depth
WB not in contact with sea floor = deep water
WB in contact = shallow water

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8
Q

Surf Beat

A

the alternating arrival of higher and lower sets

can either result in long lulls or rouge waves when crests and troughs align

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9
Q

Stokes’ Drift

A

something sitting on the surface will move forward along the wave

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10
Q

Wave Length

A

Distance between successive waves

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11
Q

Wave Period

A

Time between successive waves

(easiest to measure

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12
Q

Spilling Waves

A

Shallow flat beach (piha)
Waves break a long way out
Wide surf zone

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13
Q

Surging Waves

A

Very steep beach (Napier)

Waves dont encounter sea floor until last minute

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14
Q

Infragravity Waves

A

Water trapped in the swash zone (btw 1st breaking wave and swash zone)
long period, low frequency (100 secs wave period)
moving back and forth, sea surface going up in down like when you hop into a bath tub
Results in the odd wave that travels further up the beach

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15
Q

Wave Refraction

A

Waves bending in response to different wave depths
Affects the distribution of wave energy on the shoreline
As a wave refracts more it becomes more parallel to the shore

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16
Q

Wave Diffraction

A 
Wave crests are broken into segments and redirected by an obstacle
Wave shadow (quiet water) is created behind the obstacle some wave energy may leak into shadow area
After obstacle wave segments may recombine

EG: Rabbit island and A frame

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17
Q

Wave Reflection

A

Waves bounce or reflect off a shoreline
may result in an edge wave that travels along the shore (backwards waves colliding with wave then travelling parallel to shore)

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18
Q

Longshore Feeder Currents

A

carry water along beach into rips

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19
Q

Longshore Currents

A

Wave induced current flowing parallel to shore in breaker zone
velocity of longshore current increases as the angle of the wave approach increases and wave height increases
Can skew rip systems

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20
Q

Mass Transport

A

Slow onshore movement of water

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21
Q

Rip Head

A

seaward end of rip current

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22
Q

Bed return flow

A

transports sediment offshore / undertow
always present under breaking waves
fed by water carried to the shore by breakers

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23
Q

Swash Zone

A

upper part of the beach that is alternatively wet and dry

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24
Q

Dissipative beach

A 
High energy
Flat gradient
Wide surf zone
Smaller sediment
Spilling waves
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25
Reflective beach
``` Low energy Steep gradient Very narrow surf zone Larger sediment Surging waves ```
26
Winter (storm) profile
``` High storm waves Offshore Sand transport Beach erosion Longshore Bar Accretion Low beach gradient ```
27
Summer (swell) profile
``` Regular, low wave conditions (swell) Onshore sand transport beach construction Berm build up Steep beach gradient ```
28
Percolation
the rate at which water will pass through a sediment | Greatest for coarse materials and less for finer materials
29
Berm
swash deposition nearly horizontal often slopes away from sea opposite to beach face
30
Angle of repose
angle at which loose material can maintain a slope (due to internal friction) Dry sand = 30 - 34 degrees
31
Storm Surge
pressure set up + wind set up (most damaging when combined with high tide)
32
Flocculation
- clay and silt particles have negative ions - remain individual ions in fresh water - saltwater has positive ions (Ca, Mg, Na) - the particles bind together in salt water due to the electrical attraction - thus come out of suspension and sink to the floor creating mud
33
Residual Current
more dominant in a partially mixed estuary where there is a lot of mixing (potentially look at lab material and assessment to find more)
34
Turbidity maximum
Suspended fine sediment from both directions/ sources meeting in the middle Occurs at the limit of salt water
35
Shore platform
Rock surface that forms at mean tidal level is foot of the cliff is left behind as rocky coast erodes Erodes quickly due to the tides causing water-layer weathering (alternate wetting and drying = expansion, contraction, break up of rock)
36
Bio-erosion
``` Caused by marine organisms (invertebrates) either Chemical (dissolving) or Mechanical (burrowing) ```
37
Mass movement
The erosion of the a rocky coast can take place over a long period of time but mass failure can occur changing the coast suddenly
38
Salt water PPT
35 ppt
39
Fresh Water PPT
0-0.5 ppt
40
Thermal expansion
surface of ocean expands due to heat | hence the water at the equator is elevated as it is warmer
41
Glacio-eustasy
global rise and fall in sea level caused by melting and expansion of ice sheets
42
Glacio-isostasy
rise and fall in land caused by melting/expansion of thick ice sheets Isostatic rebound (weight of ice on land depresses land into fluid mantle (sinks) ... when ice melts weight is lifted and the crust moves/ rebounds back up) Rebound is greatest in the centre and decreases towards the coastline coast effectively sink which means sea level rises
43
Transgression
Coastal retreat as the sea level rises the coastline retreats landwards taking sediment with it. New beaches forming and old coastal features left behind
44
Regression
Coastal advance As sea level falls the coastline is able to advance (also occurs when sea level is stable when there is an abundance of sediment)
45
Pleistocene
10,000 to 1.8 million years ago
46
Holocene
present to 10,000 years ago
47
Key dates and facts?
-1870 we started recording sea level -Auckland sea level has risen 16cm in last century -18000 yrs ago the sea level was 120 meters lower than today NZ and Aus sea level has risen 1.3m per century since the last glacial period Sea level reached it current positon 6000 yrs ago (sea level stillstand)
48
Wind set up
results in surface tension between air and water over a distance (fetch) will produce a wave (longer distance = longer wave)
49
Pressure set up
``` Storm = low pressure system low = less weight pressure holding down water = elevated sea high = more weight/ pressure = calmer less elevated sea ```
50
Storm surge
wind set up + pressure set up | most damaging at high tide
51
Sea wall
to build a large wall to protect the land behind the beach (hard structure approach) rubble is often put in front of wall to prebreak the waves Work by reflecting destructive wave energy Problems: can result in beach loss reducing deposition of sediment in normal conditions
52
Groyne
The construction of a structure perpendicular to the shore Designed to catch sediment moving alongshore (hard structure) Slow longshore currents that carry sand = less sediment carried = sand is trapped and deposited. Problems: While sand collects on the updrift side, the downdrift side is deprived of sand
53
Breakwater
To protect the shoreline by creating a structure that reduces incident wave energy (also used to create artificial harbours, surfing reefs) hard option
54
Beach Replenshment
To replace lost sediment by placing new sediment on the beach (soft option) however it is only Problems: Temporary, needs to be carried out periodically Expensive Sand has to come from somewhere and needs to be a constant supply (can be cost effective when paired with existing estuary dredging programmes)
55
Dune Rehabilitation
Replanting sand dunes to help recreate natural dune systems have fences and access tracks to protect dune vegetation Vegetation stops sand from blowing away Popular soft form of CM as it involves communities
56
Accommodation (in the context of coastal management)
learning to live with sea level rise and coastal inundation (elevating buildings, coastal warning systems)
57
Set back zone
minimum distance from the shoreline for infrastructure to be built Problems: difficult to do in already developed land also not very popular
58
Mixed Layer
the upper part of the ocean (in direct contact with the atmosphere) Approx 50 meters deep (varies, seasonal changes) Characterised by nearly uniform properties (temperature, salinity etc) Dramatic increase in salinity and decrease in temperature as you travel deeper seasonal variation has consequences on marine life. During summer they thrive but in winter there are more storms = more wind = more mixing = deeper mixed layer = phaeto plankton sink too deep and get less sunlight.
59
Coriolis Force
created by the earths rotation whereby moving objects (winds, tides, ocean currents) are deflected left or right Northern Hemisphere = deflect to the right Southern Hemisphere = deflected to the left only appears on large bodies of water
60
Subtropical gyre
``` huge circular surface currents -North Pacific -North Atlantic -South Pacific -South Atlantic -Indian Ocean Ekman Transport and winds (trades and westerlies) piles up water approx 2m high = subtropical gyre returns warm water towards poles ```
61
Gulf Stream
an example of a western boundary current Water in subtropical gyres is returned to poles along westen boundary currents they are strong (1-2 m/s) narrow (100 - 200 km) and warm (moving water from tropics to the poles this explains why places like the UK are warmer than Alaska despite being at a similar latitude. Due to gulf stream going past UK radiating heat to surroundings
62
Antarctic Circumpolar Current
Flows clockwise around Antarctica Keeps warm water away from Antarctica (vital to prevent ice melting) Connects all oceans and is principle pathway of exchange
63
Thermohaline circulation
deep ocean current (influence 90% of ocean) returns oxygen to deep water and brings nutrients to the surface very slow 10 - 20 km per year hIgh salinity water cools and sinks in north atlantic flows along deep ocean currents upwells and returns to surface in indian and pacific oceans
64
Bathymetry
Under water topography | eg affects deep water currents

Geo 101 (3 decks)

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