Rob 1 Flashcards
1
Q
Where does the coastal zone start?
A
Where waves start hitting the ocean floor and consequently move sand - wave base
2
Q
How does where the coastal zone starts vary?
A
Depending on wave size. The wave base will be further out from the beach if wave size is larger
3
Q
What are waves?
A
circular motion of water particles which moves sediments
4
Q
What happens to wave size as you move further from the waters surface?
A
The waves get smaller and smaller
5
Q
Coasts are dynamic! How do we study them?
A
On a temporal (sec/min/hour/day/yr) and a spatial scale (length scale)
6
Q
When studying coasts on a temporal and spatial scale what are the 4 categories you end up with?
A
- Insantaneous
- Event -Engineering - Geological
7
Q
What did the first people who studied coastal science do?
A
They made things up because they didn’t have instruments to measure variables
8
Q
Darwin
A
Travelled through south pacific on his journey and saw a lot of coral reefs. Came up with theory about how coral reef forms. Came up with 3 ideas of the reefs and said they were related because the island sink
9
Q
Darwins 3 types of coral reef
A
- Fringing: coral reefs stuck to shore lines of islands
- Barrier: separated from island by lagoon
- Atoll: circular ring of reef
10
Q
Why will coral be left behind if a island sinks
A
Coral grows to the surface of ocean so if a island sinks the coral will remain. Islands sink because they are sitting on tectonic plates
11
Q
What is darwin’s theory of coral reef evolution a example of
A
Just coming up with a observation and then it being right
12
Q
WW2
A
Any war - exhilaration of technology. ww2 d-day invasion alot of time they hit a sand bar of shore. Hit deep trough between sand bar and tough = drowning. Due to a lack of understanding about coastal sandbars.
13
Q
Following WW2 what happened and why?
A
Military had a perspective that they needed to know more about the coastlines and waves. Start measurement programme that all of the american coastline was surveyed. Mapped out the coastline = empirical approach
14
Q
1960’s
A
Took 2 approaches
- Sedimentary (geological) approach (1960+)
- Geophysical Principles approach
15
Q
Sedimentary / geological approach
A
From the 1960’s- look at the size and angle of sand particles. Use cores- sediments and statigraphy
16
Q
Geophysical principles approach
A
1960+. apply physical principles of matter and motion - look at water motion over sand and how sand is suspended
17
Q
1970’s
A
Morphodynamic Approach
18
Q
Stratigraphy
A
Branch of geology concerned with order and relative position of strata
19
Q
1970/morphodynamic approach : what does it say
A
All these enviro controls on a coastal system. The system is like a engine and upi have processes like waves and currents and tides which are moving and driving sand. Movement will change shape of beach and different shaped beach will affect the processes. A interconnected system
20
Q
What does the interconnected morphodynaic approach mean for humans?
A
If humans alter something it will change everything else. Understand 3 boxes
21
Q
Processes drive…
A
..the sediment transport.. which drives the beach morphology.. drives the processes (interlinked)
22
Q
Coastal controls
A
- Geology
- Sea level
- Wave climate
- Tide range
- Daily processes
23
Q
Geology as a coastal control
A
Hard rock - coastlines don’t change often!
Soft rock - coastlines change alot!
24
Q
The different scales as geology as a coastal control
A
- Global : plate tectonics
- Regional: Continental shelve and sediment type
25
CC - Geology : plate tectonics
GLOBAL scale! Boundaries of tectonic plates tend to be on coastlines, e.g. west coast of NA. NZ has plate boundary through it. Get 2 types of coasts based on where the coast is relative to plate boundaries
26
CC - Geology - 2 types of coast:
- Collision Coast
- Trailing edge coast
* under different pressures = get different looking coastlines
* end up with different appearances
27
Collision coast
2 plates smashing in to each and the light plate will go under the heavier one. Friction. Cause mountain building and volcano's
28
Appearance of a collision coast
Mountainous. Beaches but generally not alot of sandy beaches
E.g. NZ - Rocky -Steep -Mountainous
29
Appearance of trailing edge coast
Flat
Alot of sand
E.g. florida
Alot of dunes
30
Continental shelve she
Every coastline has one. Where the coast just drops of into the beach deep ocean. Different places in world have different extent of coastal shelve. Sydney has a very narrow continental shelve
31
NSW gets good surf bc
V narrow continental shelve and v steep! Waves coming in - nothing slows them down!
32
Why are Continental shelves important?
- Surf
| - Tsunami
33
Tsunami and continental shelve
Suited to a wide continental shelve - make them get bigger ! = NSW via its geology is totally protected from a large impact of a tsunami
34
Final geological control is..
The sediment type .. on a regional scale!
35
What are the different types of sediment
Gravel
Sand
Mud
Bioclastics
36
Tropics beaches
Wet and hot! alot of mud! Not great beaches
37
Gravel
Mostly in coastal area's which have been glaciated. Not many in Aus because old country but NZ is a relatively new country so they have lots of gravel beaches
38
Sand
Mostly in the lower and middle latitudes
39
Mud beaches
most common in humid, temperate or tropical hot climatic zones
40
Bioclastics
Bits of shells and coral
41
What is the second control about what the coastline looks like?
Sea level!
42
Quarternary and sea level
Period which goes back the last 2 mil years - sea level has been going up and down like a yoyo
43
Where the sea level is today
Unusual in terms of where it has been in the past! Its only been at its present location a few times in the Quaternary period
44
Why does sea level change
- Movement of plates, e.g. more volcanic activity changing temperature (ice).
- Astronomical : earth rotates round the sun but it goes as a elipse : eccentricity. And it tilts and wobbles. Sometime eccentricity, tilt and wobble line up and the earth is closer to the sun! Earth gets warmer and the ice melts! Roughly happens 40,000-60,000 years apart - regardless of CC we will eventually get a ice age
45
Eustasy
Means a global change
46
Glacio-Eustasy
When earth gets cold and have ice at poles sea levels worldwide will fall by about 100 metres
47
Isostasy
Local change in sea level. Ice is really heavy!
48
Isostatic rebound
After ice pushing down a continent when the ice melts and pushes the coast back up! It called isostatic rebound
49
Isostatic rebound makes the sea level look ..
.like its falling
50
What are the 2 main effects of ice on the coastline
Ice affects the volume of water in the ocean
| -The ice affects the rebound of shorelines
51
Hydro-isostasy
Water is heavy. The weight of water can push down the continental shelve a little bit - looks like sea level is rising
52
Sediment Isostasy
Sand is heavy. Push down! New Orleans
53
What happens if you heat up water?
It expands
54
Tectonic plate
Earth quake pushes up a big section of land! Makes the sea level look like it has gone up or down
55
Ocean temperature
If the ocean temp increases by 1 degree it will cause sea level to rise by 2m
56
Scotland
been going through a isostatic rebound since the last ice age
57
The story of bondi beach
Go back 18,000 yr ago! Had a ice age- sea level is 120 metres lower ! Sydney harbour was dry! Could walk to tasmania.
So 18,000 years ago bondi beach would have been a woodland. Had big rivers coming down and carrying sand from outback which was dumped on beaches! When sea level rised the sand got pushed back into the old river valleys
58
Why geology is important
It gives the shape of the coastline, e.g. old ancient river valleys - have little pockets for the sand to go into and create beaches
59
Bondi sand
Bondi sand has came from the coastline
60
Sea level rise between 18,000 years ago and 6,000 years ago was...
..way faster than anything we predict today due to anthropogenic climate change
61
Sea level change.. in the past
1800's didnt have instruements to tell us what was going on so guessed! Then we developed tide gages in last 100 years - predictions got good -
62
What does the tide gages tell us about climate change in the last 100 years?
That sea level has gone up by about 100cm
63
We know sea level is rising but..
..even the best scientists globally don't know by how much. Some people think its a couple of cm..others think metres! uncertainty!
64
What does the uncertainity mean?
No politician will invest in sea level rise- why it is important that we get better at predicting it
65
What is the 3rd coastal control?
Wave climate, e.g. average wave height, direction and often but may have storms super imposed on this. There are different wave climates around the world
66
What wave climate categories have been produced
- Storm waves
- Protected sea's
- East coast swell
- Cyclone influence
- Monsoon/trade wind influence
- West coast swell
67
lower latitudes
- windy
| - roaring 40's
68
wind =
waves
69
Big difference between north and south
The north has more land - northern hemisphere - dont have as much waves
70
Wave climate depending on where you are..
Different areas will have different wave climates!
71
What is the fourth coastal control?
Tides
72
Do all places have tides?
no - e.g. great lakes and Mediterranean sea
73
What are tides created by?
Created by the moons gravitational control on the water
74
Tide reach
How much the tide goes up and down- some places have huge tides!
75
Tide range..
..varies globally
76
What do tides have a impact on?
What your coastline looks like
77
Different landforms will form as a consequence of..
..the predominant tide
78
tide v wave dominated
cape cod: wave dom- big waves and big beaches and big sand dune
bay - protected from waves and different beach
ONLY DIFF IS TIDE DOMINANCE V WAVE DOMINANCE
79
What is the fifth/final coastal control?
Daily processes
80
Describe daily processes as a coastal control!
-Waves
-Current -Tide -sand transport
(every day you go to the beach its different - this could be a subtle or a dramatic change) `
81
Motion in the ocean
-
82
For every wave there is a ..
explanation
83
Wave height (H)
distance between crest and trough
84
Wave length (L)
horizontal distance between 2 consecutive wave quests
85
Wave period (T)
time between consecutive wave crests passing a fixed point
86
H L and T ..
very simple to measure and used in most equations to predict how fast waves move across a ocean
87
2 things moving when you sea waves
Water particles are trapped in spirals!
88
What happens when waves are in shallow water
The motion starts to hit the bottom and this causes friction and the waves start to slow down and then the waves get bigger and bigger over time
89
How are waves formed
via wind and the transfer of energy from wind to the waters surface
90
What is wave size dependent on?
```
Wind speed (faster--> bigger)
Wind duration (longer --> bigger)
Fetch (bigger--> bigger)
```
91
What is fetch!
The distance over the water which the wind can blow
92
There are different types of waves
-Wind
93
Wind waves
Wave period is between 3- 8 seconds! Can see them being formed by waves in front of your eyes! Short and choppy! The ocean doesnt like to be messy but wind is giving the waves the energy
94
What happens the more waves travel
Wind waves --> sort themselves out and become more organised ! They become swell waves
95
Swell waves
Formed by wind but they have travelled thousands of km. On top of swell waves you can get wind waves
96
Wave shoaling
When the waves start to slow down. The motion at the bottom of waves start to hit the bottom- wave refraction
97
what is wave refraction?
When the waves start to bend - different bit of waves are moving at different speeds
98
When waves break they break in a couple of ways
- plunging
- spilling
- surging
99
Plunging
Curls over and crashes down with great force. Waves come in and go from deep to shallow water over a short distance ! good for surfing! dangerous!
100
Spilling
safer - need a nice flat beach! break gently! Good for learning to surf! not about the wave size its about the shape of the beach
101
Surging
bulges and then collapses and rushes up beach quickly and then washes back v quickly ! knock over people! minature version of a tsunami
102
Clapotis/ wave reflection
big waves comes in and smashes against rock! next waves come in and they smash together and get alot bigger!
103
Tides
ocean going up and down. big difference between high tide and low tide.
104
why are tides complex
involve interaction between the sun and the moon and the earth
105
Are tides predictable
yes v v v v
106
how do tides work?
Have earth- alot of water and the moon which is exerting a gravitational pull on the water. As move goes around earth it is dragging bulge of water with it. At the same time the earth is rotating
107
Why does the timing of the tide change?
Because the bulge is moving around the earth all the time! moon moving around earth and the earth rotatingg
108
What changes everyday
- timing of tide
| - height of time
109
What is the tide range
vertical distance between high tide and low tide
110
why is the tide range different everyday
because of the sun and it exerting a gravitational pull on the water
111
What happens when sun and moon align
Create bigger buldges which create bigger tides = spring tides
112
Spring tides
high tides are higher and the low tides are lower
113
Neap tides
high tides doesnt go far, small tides doesnt go very far = small tide range
114
Lunar cycle takes.. what does it mean
28-29 days - predictable - around full moon and new moon you get big tides
115
King tide
Big spring tide bc twice a year the moon is particularly close to the earth
116
The tides around the world
The tides change around the world
117
What is the tidal range at a location on the globe influenced by?
- Ocean bathymetry
- amphidromic points
- coastal configuration (refraction)
- continental shelve width (shoaling)
118
what do we need to know about tide range?
there are different tidal points, called amphidromic points, all over and depending on how close you are to the point will affect the time of your tides
119
Surf zone is dominated by
wave breaking
120
When waves break what do they release?
Energy and water released
121
What does white water tell you?
The wave has broke and water has been let go!
122
Wave set up is..
when waves break the level of surface water rises - by about 10% of wave height
123
Why do you have currents?
BEcause can't just have water piling up all the time needs to go out someway!
124
Why do currents exists
due to the spatial gradients in the mean water surface level due to difference in wave breaking/wave set up
125
more wave breaking =
more wave set up
126
The strength of current flow increases as...
the amount of wave breaking increases
127
Different types of currents
- longshore current
- bed return flow
- rip currents
128
Long shore currents
Need long and flat beaches.
Need waves to come it at a oblique angle to the beach = water pilled up and pushed along! End up being way down the beach.
Go fast and carry sand = studied alot!
129
Fraser island
Sand island - sand gets dumped here because of the great barrier reef! All sand here at some point was at NSW - show important of long shore currents and wave breaking
130
Is there anything in the ocean which pulls you under no?
No!
131
Bed return flow
Under the water moving to surface there is a flow of water (knees down) moving back out to sea)
132
Where does bed return flow occur?
On every beach on the planet which has breaking waves
133
Sand bar
ridge of sand built up by currents especially in a river
134
What is between sand bars?
A trough - where a rip current will occur!
135
Are rip currents strong?
yes strong and fast
136
Rip current prevalence?
They occur on all beaches. Less prevalent on long beaches as long beaches are dominated by long shore currents
137
On most beaches which is your main beach type
Wave
138
What is the effect of small waves breaking on wave set up?
Make small wave set up --> don't raise the water level very much at all!
139
What are the 3 stages of rip
1- longshore feeder currents (most rips start by flowing along the shoreline)
2-rip neck
3- rip head
140
Rip neck
Offshore flowing rip neck - narrow - fastest part of flow
141
Rip head
Expand and slow down
142
Do all rips go staight?
Nope
143
what happens when rips go out?
sometimes they go straight out and sometimes they recirculate? We never really know exactly what they are gonna do?
144
Rip pulse
Rips double in pace - normally bc had some bigger waves come in
145
There are different types of rip currents.. what are they/
- channelised rips
- boundary rips
- flash rips
- mega rips
146
C-Channelised rips
most C-common
Controlled by morphology : sit in deep channels (green gaps)
Persistent in time and space -can sit in same place for days/weeks
-flow quickly
147
Boundary rips
next to physical boundaries , e.g. headlands or jetties! as the water gets pushed against the boundary the water has nowhere to go! there all the time! they are given names, e.g. backpacker express = dont swim against headlands
148
Flash rips
Produced by waves, rather than landforms and morphology
- mobile/dynamic in time and space
- might be due to loads of big waves!
- unpredictable
- happen when its stormy and messy
149
Mega rips
Uncommon
-Due to big waves! higher than 3 metres! the wavves which erode houses! not dangerous to people bc would have to be a idiot to be swimming
150
beaches are all different - what is one way we can describe beaches?
in there slope! - some beaches can be very steep! Some can be v flat
151
What will a beach slope affect?
Affect waves and currents
152
Which beaches are steep?
ones made up of coarse material
153
Which beaches are flat?
ones made up of fine material!
154
Beaches have a lot of what on them?
features
155
What features do you
-stand bars - ripples - rip channels -runnels -berm -megacusp
156
sand bar
- deposits of sand off shore which are underwater most the time
157
berm
raised mound around the high tide line - bc every wave which comes up dumps sand
158
The amount of sand on the beach is normally related to what?
how much sand is in water - normally in sand bars
159
Normally find that if you have a big berm ..
you dont have much sand offshore
160
If you have a big storm it chews up all the sand and ..
dumps it out in the sand bars
161
berm/bar relationship
when you get big waves they take sand from the berm and they put if offshore in sand bars! when gentle waves the sand gets moved from the bar to the berm
162
What are the different types of beaches
Different materials
163
What are the main ingredient which determines how a beach looks
- sand size
| - wave height
164
Palm beach
one side gets big waves - good at moving sand around so you get a big wide beach! Small waves - narrow beach!
165
What are the different scientific types of beaches?
-dissipative -reflective -intermediate
166
What is a dissipative beach?
-A beach which has big waves and fine sand
167
What is a dissipative beach?
-A beach which has big waves and fine sand = wide and flat beach! (lots of energy dissipated by the breaking waves) -stable beaches which tend to look the same everyday! Big waves
168
Reflective beach
Steep and narrow
- small waves (steep)
- coarse sands/shell
- beach cusps
- stable
169
Intermediate beach
- beaches which change
- medium sized waves
- medium sized sand
- have sand bars and rip currents
170
Different types of intermediate beaches are..
LBT - long shore bar trough
RBB- rhythmic bar beach
TBF- Transverse bar rip
LTT- low tide terrace
171
RBB
rhythmic sand bar
172
TBR
Transverse bar rip! Sand bars are transverse to the beach
173
LTT
low tide terrace - low tide and flat terrace
174
What do small waves do?
bring sand back to the beach
175
intermediate beach behaviour
can change between types - no way of predicting because depends on what the waves are doing which depends on the wind
176
Tidal range determines
how long shoaling, surf and swash zones act on the beach
177
shoaling
increase in wave amplitude that happens when water waves
178
what do big tides do?
bulldoze the beach flat
179
Why is coogee different
wedding cake island - blocks coogee from having big open ocean swell = small waves ! = steep beach
