Waves Flashcards
1
Q
what is a shoreline
A
a dynamic interface between air, land and sea
2
Q
are shorelines static
A
NO
2
Q
how are shorelines being modified
A
by waves
3
Q
are coastland landforms stable
A
NO - relatively fragile
4
Q
are costal zones experiencing more or less human activity
A
MORE human activity
5
Q
what determines the size and type of wave
A
fetch and wind speed
(how long and fast wind has travelled)
6
Q
what is fetch in terms of wave type
A
the distance ON WATER that wind has travelled (how long the wind has been blowing over water)
7
Q
two types of waves
A
destructive and constructive waves
8
Q
how are destructive waves formed
A
when the backwash is STRONGER than the swash
9
Q
what is backwash and swash
A
backwash = water coming off the beach that removes material with it
swash = waves that come ONTO the beach and bring material
10
Q
what features do destructive waves form
A
erosion because they remove more material than bring o
11
Q
how are constructive waves formed
A
when the swash is STRONGER than the backwash
12
Q
what features do constructive waves form
A
depositional features because they bring more material than remove
13
Q
describe the wavelength and frequency of destructive waves
A
they have SHORT wavelength = HIGH frequency
14
Q
what happens to the height of a destructive wave as it comes near/onto the beach
A
the height increases and the wavelength decreases
15
Q
do destructive waves travel far up the beach? why or why not?
A
NO - all their energy is directed downwards so it cannot get far up the beach
16
Q
what is a visual indication of destructive wave
A
whitecaps
17
Q
A
destructive wave
18
Q
A
destructive wave
19
Q
describe the frequency and wavelength of constructive waves
A
have a LONGER wavelength so have a LOWER frequency
20
Q
do constructive waves travel far up a beach
A
yes
21
Q
what type of wave has higher frequency
A
destructive wave
22
Q
what type of wave has a longer wave length
A
constructive waves
23
Q
which wave type travels farther up a beach
A
constructive waves
24
constructive waves
25
constructive waves
26
what kind of beach does a constructive waves form
wide sloping beach
27
what kind of beach does a destructive wave form
steep beach while scouring out the area in front
28
what wave type has higher energy
destructive waves
29
what wave type has lower energy
constructive waves
30
what are 4 erosional processes caused by waves
hydraulic action
abrasion
solution
compressed air
31
describe hydraulic action erosion
the power of the wave itself carries away loose material (the impact of the wave on the rock)
32
describe abrasion erosion
the waves contain small particles (like sand) and use that material to break rock down into smaller fragments
33
describe solution erosion
the water dissolves soft rock
34
describe compressed air erosion
impacts of waves on rocks causes cracks to form which fill with air, the next wave to hit the cracks causes the air to compress and the rock cracks more
35
what do the erosion rates depend on
- rock type (softer rocks erode faster)
- degree of exposure (how much the rock is exposed to waves)
- amount of protective interference by man
- wave type
- slope of shoreline
36
how does the slope of the shoreline affect the rate of erosion
stepper slopes have more erosion
gentler slopes have less erosion and more deposition
37
what is the consequence of man made structures to protect beaches and shores
building to protect one beach decreases the rate of erosion on it HOWEVER it would increase the erosion at adjacent beaches
38
what is differential erosion
the idea that bands of hard rock and soft rock erode at different rates
39
what are the processes involved in the formation of bays and headlands
the same processes as erosion
(hydraulic action, abrasion, solution, compressed air)
40
what forms headlands
hard rock that resist erosion better than soft rock
41
what forms bay
soft rocks that have erode more and retreat inland
42
headlands
high steep faced cliff that protrudes into the sea
43
bay
a wide, inward curve of the coastline between headlands and are points of deposition
44
Bay
45
Headland
46
do headlands receive high or low energy waves
high energy waves
47
why do headlands receive high energy waves
as bays retreat inland, wave refraction occurs which has headlands receiving more high energy waves
48
do bays receive low or high energy waves
low energy
49
where is erosion concentrated (bays or headlands)
headlands
50
where do waves erode headlands
along lines of weakness (joints, faults...)
51
describe the process that happens to form bays and headlands
over time the less resistant rock to weathering begin to erode faster than the more resistant rock
the heavily eroded rock retreats inward while the more resistant rock DOES NOT
the eroded rock moved inward becomes bays that are sheltered by headlands
the headlands are left more vulnerable to erosion and wave energy is concentrated there
52
is the formation of heads and bays a negative or positive feedback
positive
(as more refracted waves hit the headlands, they begin to erode and bays would receive more wave action. Resulting in bays retreating further inland and headlands forming again)
53
describe the evolution of caves, arches and stacks
waves attack the weak areas of exposed rock which widens the cracks and begins the process of cave formation
waves cut further into the base of the cliff by abrasion which deepens the cave
when the water erodes through the cave to the other side WITHOUT collapsing an ARCH is formed
as erosion and gravity increases it causes the cave's roof to collapse, the arch falls apart and a stack forms
as the stack continues to erode top down a SEA STUMP forms
54
sea arch
55
sea stack and slumps
56
what is a cliff
a high, steep rock face along a coast
57
how do cliffs differ from headlands
the waves are directed right at the cliff and NOT hitting the land at an angle (refracted waves)
58
what wave type forms sea cliff
destructive waves
59
what are the erosional process to form sea cliffs
same 4 erosional forces
(hydraulic actions, solution, abrasion, compressed air
60
what is indicative of an inevitable sea cliff
a notch that is carved out and enlarged ALONG the cliff
61
describe the process of sea cliff formation
destructive waves attack the coast
the 4 erosional process work at eroding along the coast
a notch forms at the base of the coast and enlarges
the upper lope becomes unsupported through undermining, erosion, weathering and will collapse to form a steep face
62
what happens to a cliff as it retreats inland
it increases in height
63
what is the rock left at the base of a retreating cliff called
a wave cut platform
64
describe the relationship between a wave cut platform and erosion
as a sea cliff retreats (has fallen often), its wave cut platform increases = fewer waves can reach the sea cliff and erosion DECREASES
65
are wave cut platforms ever exposed
yes - during low tide
66
sea cliff with notch
67
why do cliffs retreat inward
due to constant erosion
68
what forms at the base of the cliff
a gently sloping surface (wave cut platform) with the cliff behind it
69
what are the 4 main shoreline features/zones
offshore zone
shoreface
beach (foreshore and backshore zones)
70
offshore zone
the area based on fair weather that is submerged AT ALL TIMES
71
shoreface
the shore that is exposed periodically based on high and low tides between the offshore and beach
72
what shoreline zone has the most sediment transport
the shoreface
73
when is the shoreface seen
at LOW tide
74
foreshore vs backshore zones of beach
foreshore
- area affected by swash and backwash of breaking waves and is seen at LOW TIDE and covered at HIGH TIDE
backshore
- a beach zone that is ABOVE the normal high tide (always exposed EXCEPT for storms)
75
what does feeling bottom refer to
when the waves height/depth allows them to come in contact with the sand bottom
76
when does feeling bottom usually occur
when the offshore zone and shoreface zone meet
77
1
offshore
78
2
shoreface
79
3
foreshore
80
4
backshore
81
what is longshore drift
a movement of material ALONG the coast in a zig-zag pattern
- where swash moves material UP the beach
- backwash moves sediment BACK into the sea
82
what direction does the coast move with the longshore drift
in the direction of the longshore current
83
is the longshore drift current based on destructive or constructive waves
constructive waves - based on deposition of material NOT removal of material
84
what wave type forms beaches
constructive waves
85
how are beaches formed
weak backwash allows material to BUILD UP HIGHER up the shore and FINER material is left closer to shoreline
86
what material usually makes up beaches and why
finer material (easier to move and requires less expansion of energy)
87
what are 3 shoreline features
spits
baymouth bar
tombolo
88
what are spits
elongated rides of sand extending from land INTO the mount of a bay (often end curves inward to the bay)
89
baymouth bar
when a sandbar (spit) completely crosses a bay
90
Tombolo
ridge of sand (stump) that connects an island to the mainland or another island
91
spit
92
baymouth bar
93
tombolo
94
how do sand spits form
through constructive waves and longshore drift
95
how do waves deposit material
waves travel with high energy initially but hitting an obstacle (slower energy water, solid rock...) causes the wave to lose power and deposit their material
96
why do sand spits sometimes curve inwards towards the bay
when wave refraction hits the spit and causes the sand to start building up on a curve
97
are baymouth bays completely solid
NO - they have an opening for water movement
98
what are baymouth bars often associated with
tidal deltas
99
what are tidal deltas
areas where high energy moving water comes in contact with slower moving water so the waves deposit material INSIDE and OUTSIDE of lagoons
100
two kinds of tidal deltas
flood tidal delta and ebb tidal delta
101
flood tidal delta
deposits of sand on the INSIDE of the baymouth bar (lagoon side)
102
ebb tidal deltas
deposits of sand on the OUTSIDE of the baymouth bar (ocean side)
103
how are flood tidal deltas initiated
during storm surges
104
how are flood tidal deltas maintained
by flood currents
105
how are flood tidal delats stabilized
when salt marshes establish ON them
106
why do salt marshes stabilize flood tidal deltas
their grasses cause the land to be built up to high-tide level and new land is added to the island
107
what do ebb tidal deltas form most commonly
high energy environments
108
how do ebb tidal deltas form
where they interact with waves and longshore current
109
what are the shoreline features
- spits
- baymouth bars
- tombolo
- tide deltas
- barrier islands
110
what are barrier islands
low ridges of land that PARALLEL the shore and are separated from the shore by lagoons
111
what are barrier islands similar to
baymouth bars
112
how are baymouth bars and barrier islands similar
a barrier island is what a baymouth bar becomes when it's more stable and permanent
113
what are barrier island composed of
sand, and other materials errored away and brought to that location
114
barrier island
115
how are tombolos formed
constructive waves and longshore drift
116
describe how tombolos have a buildup of sand
based on wave refraction at the island causing currents to converge and influence more deposition of materials
117
describe the entire evolution of a coastline
a) headlands and bays form through differential erosion with features like sea stacks and slumps
b) spits begin to form across the bays and tombolo form to connect stacks/slumps to the mainland. headlands also undergo evolution in forming caves and arches
c) the spit continues to grow across the bay, the headlands that formed caves and arches collapse to form stacks and stumps. the tombolo becomes submerged and wave-cut cliffs and their wave-cut platforms begin to form through high tidal erosion.
d) the longshore current continues to wig wag beach material where the once spit becomes a baymouth bar and a new spit forms down the beach. Wave-cut cliffs continue to form down the beach.
118
what will a shore become if it remains stable
a straighter, more regular coast where the headlands have been eroded and bays deposited
119
how to distinguish an old vs young coastline
young -
undulating shoreline of headlands and bays and other shoreline features
old-
straighter more regular coastline with bays filled in and headlands erorded
120
what are some factors that influence shoreline erosion
1. proximity to rivers with lots of sediments and materials
2. degree of tectonic activity (is land moving up or down)
3. topography and composition of land
4. wind and weather patterns
5. how coastlines are configured (young vs old)
6. human activities
7. sea level changes
121
how do gentle and steep nearshore slop affect wave feeling bottom
steep
- waves will feel bottom much later (closer to the beach) which means they will hit the beach with more energy
gently
- waves will feel bottom farther out in the ocean so when they reach the shore they have LESS energy
122
what are two methods of shoreline stability
hard and soft stability
123
what is hard stabilization for shoreline stability
any form of ARTIFICIAL structure built to protect a coast or prevent movement of sand along beach
124
what are examples of hard stabilization
- groins
- jetties
- seawalls
- breakwaters
125
jetties vs groins vs breakwaters vs seawalls
jetties
- built in pairs to extend into the ocean to disrupt the movement of sand
- the one of up current side has sand deposition while the other faces sand erosion
groins
- built at right angles to maintain or widen beaches
breakwaters
- updrift side has sand deposition
- downdrift side has erosion
breakwater
- barrier built OFFSHORE PARALLEL to the shoreline to deflect waves and break up destructive waves before reaching beach
seawalls
- built along beach ON SHORE to protect property by reflecting the force of breaking waves
126
are hard stabilization techniques effective
NO
127
soft stabilization alternatives
- beach nourishment
- relocation
128
what are drawbacks of hard stabilization
cost of structures
loss of sand on beach
129
relocation vs beach nourishment
relocation
- relocation of storm-damaged or at risk buildings and letting nature claim the beach
beach nourishment
- large amount of sand are added to the beach system to offset losses by wave erosion
130
what are drawbacks of beach nourishment
- not a permanent solution
(new sand to replace will eventually erode too)
- very expensive
- sand added to a new beach is NOT clean (can carry pollution and harmful organisms to that coastline)
131
2 coastal classifications based on changes in sea level
emergent coastlines
submerged coastlines
132
emergent vs submerged coastlines
emergent
- coastlines that emerge (rise) from the sea and develop because of uplift of land OR drop in sea level
submerged
- coastlines that drop into the sea because sea levels rise or land is dropping
133
which type of coastline is young and which is old
emergent coastlines are YOUNG
submerged coastlines are OLD
134
what coastline is an area of erosion
emergent coast
135
what shoreline features are on a emergent coast
headlands and bays features
136
what coast has newly exposed landscape
emergent coast
137
what coast has sunken land
submerged coast
138
what coast is an area of deposition
submerged coast
139
what features do submerged coast have
barrier islands and tombolos
140
what causes tides
imbalances between
gravitational force of moon, sun and earth
and centripetal force
141
what are tides
the daily changes in elevation of the ocean surface
142
how is gravitational force affected by increasing mass
increasing mass increases gravitational force
143
how is gravitational force affected by increased distance
increase distance GREATLY DECREASES the gravitational force
144
what do tidal bulges follow
the moon as it rotates around the earth (lunar day)
145
why are tides not the same every day
based on the lunar day and how it 50 min LONGER than a solar day (24hours)w
146
what's longer: lunar or solar daya
lunar day (by 50 mins)
147
how long is the MONTHLY tidal cycle
29 and half days
148
how often does earth alternate between the two tides
every 7 days
149
what are the two tides in monthly cycle
spring tide vs neap tide
150
spring tide vs neap tide
spring tide
- when earth-moon-sun are ALL ALIGNED there is CONSTRICTIVE inferences
neap tide
- earth-moon-sun system are NOT in line but at right angles where the lunar and solar bulges are DESTRUCTIVE INTERFERNECE
151
what tide has LARGER waves and what have SMALLER waves
larger waves = spring tide
neap tide = smaller tides
152
what has more impact of tide sizes moon or sun
moon does because despite small size its closer
153
what are three tidal patterns
diurnal
semidiurnal
mixed
154
describe the different tidal patterns
diurnal
- one high and one low tide each lunar day
semidiurnal
- two high and two low tide OF ABOUT SAME HEIGHT each lunar day
mixed
- both diurnal and semidiurnal tidal patterns with successive high and low tides have DIFFERENT HEIGHTS
155
what are tidal bores
at the mouth of an estuary where it widens because of tidal movement and the water becomes very intense
156
do most locations have one or two high and low tides per day
TWO high and TWO low
157
are two high and two low tides in the same day the same
NO - based on declination of moon and sun
