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Geomorphology > Waves > Flashcards

Waves Flashcards

1
Q

what is a shoreline

A

a dynamic interface between air, land and sea

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2
Q

are shorelines static

A

NO

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2
Q

how are shorelines being modified

A

by waves

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3
Q

are coastland landforms stable

A

NO - relatively fragile

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4
Q

are costal zones experiencing more or less human activity

A

MORE human activity

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5
Q

what determines the size and type of wave

A

fetch and wind speed

(how long and fast wind has travelled)

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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)

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7
Q

two types of waves

A

destructive and constructive waves

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8
Q

how are destructive waves formed

A

when the backwash is STRONGER than the swash

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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

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10
Q

what features do destructive waves form

A

erosion because they remove more material than bring o

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11
Q

how are constructive waves formed

A

when the swash is STRONGER than the backwash

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12
Q

what features do constructive waves form

A

depositional features because they bring more material than remove

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13
Q

describe the wavelength and frequency of destructive waves

A

they have SHORT wavelength = HIGH frequency

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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

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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

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16
Q

what is a visual indication of destructive wave

A

whitecaps

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17
Q
A

destructive wave

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18
Q
A

destructive wave

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19
Q

describe the frequency and wavelength of constructive waves

A

have a LONGER wavelength so have a LOWER frequency

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20
Q

do constructive waves travel far up a beach

A

yes

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21
Q

what type of wave has higher frequency

A

destructive wave

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22
Q

what type of wave has a longer wave length

A

constructive waves

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23
Q

which wave type travels farther up a beach

A

constructive waves

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24
Q
A

constructive waves

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25
Q
A

constructive waves

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26
Q

what kind of beach does a constructive waves form

A

wide sloping beach

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27
Q

what kind of beach does a destructive wave form

A

steep beach while scouring out the area in front

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28
Q

what wave type has higher energy

A

destructive waves

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29
Q

what wave type has lower energy

A

constructive waves

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30
Q

what are 4 erosional processes caused by waves

A

hydraulic action

abrasion

solution

compressed air

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31
Q

describe hydraulic action erosion

A

the power of the wave itself carries away loose material (the impact of the wave on the rock)

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32
Q

describe abrasion erosion

A

the waves contain small particles (like sand) and use that material to break rock down into smaller fragments

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33
Q

describe solution erosion

A

the water dissolves soft rock

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34
Q

describe compressed air erosion

A

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

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35
Q

what do the erosion rates depend on

A
  • 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
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36
Q

how does the slope of the shoreline affect the rate of erosion

A

stepper slopes have more erosion

gentler slopes have less erosion and more deposition

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37
Q

what is the consequence of man made structures to protect beaches and shores

A

building to protect one beach decreases the rate of erosion on it HOWEVER it would increase the erosion at adjacent beaches

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38
Q

what is differential erosion

A

the idea that bands of hard rock and soft rock erode at different rates

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39
Q

what are the processes involved in the formation of bays and headlands

A

the same processes as erosion

(hydraulic action, abrasion, solution, compressed air)

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40
Q

what forms headlands

A

hard rock that resist erosion better than soft rock

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41
Q

what forms bay

A

soft rocks that have erode more and retreat inland

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42
Q

headlands

A

high steep faced cliff that protrudes into the sea

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43
Q

bay

A

a wide, inward curve of the coastline between headlands and are points of deposition

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44
Q
A

Bay

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45
Q
A

Headland

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46
Q

do headlands receive high or low energy waves

A

high energy waves

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47
Q

why do headlands receive high energy waves

A

as bays retreat inland, wave refraction occurs which has headlands receiving more high energy waves

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48
Q

do bays receive low or high energy waves

A

low energy

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49
Q

where is erosion concentrated (bays or headlands)

A

headlands

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50
Q

where do waves erode headlands

A

along lines of weakness (joints, faults…)

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51
Q

describe the process that happens to form bays and headlands

A

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

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52
Q

is the formation of heads and bays a negative or positive feedback

A

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)

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53
Q

describe the evolution of caves, arches and stacks

A

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

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54
Q
A

sea arch

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55
Q
A

sea stack and slumps

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56
Q

what is a cliff

A

a high, steep rock face along a coast

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57
Q

how do cliffs differ from headlands

A

the waves are directed right at the cliff and NOT hitting the land at an angle (refracted waves)

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58
Q

what wave type forms sea cliff

A

destructive waves

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59
Q

what are the erosional process to form sea cliffs

A

same 4 erosional forces
(hydraulic actions, solution, abrasion, compressed air

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60
Q

what is indicative of an inevitable sea cliff

A

a notch that is carved out and enlarged ALONG the cliff

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61
Q

describe the process of sea cliff formation

A

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

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62
Q

what happens to a cliff as it retreats inland

A

it increases in height

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63
Q

what is the rock left at the base of a retreating cliff called

A

a wave cut platform

64
Q

describe the relationship between a wave cut platform and erosion

A

as a sea cliff retreats (has fallen often), its wave cut platform increases = fewer waves can reach the sea cliff and erosion DECREASES

65
Q

are wave cut platforms ever exposed

A

yes - during low tide

66
Q
A

sea cliff with notch

67
Q

why do cliffs retreat inward

A

due to constant erosion

68
Q

what forms at the base of the cliff

A

a gently sloping surface (wave cut platform) with the cliff behind it

69
Q

what are the 4 main shoreline features/zones

A

offshore zone

shoreface

beach (foreshore and backshore zones)

70
Q

offshore zone

A

the area based on fair weather that is submerged AT ALL TIMES

71
Q

shoreface

A

the shore that is exposed periodically based on high and low tides between the offshore and beach

72
Q

what shoreline zone has the most sediment transport

A

the shoreface

73
Q

when is the shoreface seen

A

at LOW tide

74
Q

foreshore vs backshore zones of beach

A

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
Q

what does feeling bottom refer to

A

when the waves height/depth allows them to come in contact with the sand bottom

76
Q

when does feeling bottom usually occur

A

when the offshore zone and shoreface zone meet

77
Q

1

A

offshore

78
Q

2

A

shoreface

79
Q

3

A

foreshore

80
Q

4

A

backshore

81
Q

what is longshore drift

A

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
Q

what direction does the coast move with the longshore drift

A

in the direction of the longshore current

83
Q

is the longshore drift current based on destructive or constructive waves

A

constructive waves - based on deposition of material NOT removal of material

84
Q

what wave type forms beaches

A

constructive waves

85
Q

how are beaches formed

A

weak backwash allows material to BUILD UP HIGHER up the shore and FINER material is left closer to shoreline

86
Q

what material usually makes up beaches and why

A

finer material (easier to move and requires less expansion of energy)

87
Q

what are 3 shoreline features

A

spits
baymouth bar
tombolo

88
Q

what are spits

A

elongated rides of sand extending from land INTO the mount of a bay (often end curves inward to the bay)

89
Q

baymouth bar

A

when a sandbar (spit) completely crosses a bay

90
Q

Tombolo

A

ridge of sand (stump) that connects an island to the mainland or another island

91
Q
A

spit

92
Q
A

baymouth bar

93
Q
A

tombolo

94
Q

how do sand spits form

A

through constructive waves and longshore drift

95
Q

how do waves deposit material

A

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
Q

why do sand spits sometimes curve inwards towards the bay

A

when wave refraction hits the spit and causes the sand to start building up on a curve

97
Q

are baymouth bays completely solid

A

NO - they have an opening for water movement

98
Q

what are baymouth bars often associated with

A

tidal deltas

99
Q

what are tidal deltas

A

areas where high energy moving water comes in contact with slower moving water so the waves deposit material INSIDE and OUTSIDE of lagoons

100
Q

two kinds of tidal deltas

A

flood tidal delta and ebb tidal delta

101
Q

flood tidal delta

A

deposits of sand on the INSIDE of the baymouth bar (lagoon side)

102
Q

ebb tidal deltas

A

deposits of sand on the OUTSIDE of the baymouth bar (ocean side)

103
Q

how are flood tidal deltas initiated

A

during storm surges

104
Q

how are flood tidal deltas maintained

A

by flood currents

105
Q

how are flood tidal delats stabilized

A

when salt marshes establish ON them

106
Q

why do salt marshes stabilize flood tidal deltas

A

their grasses cause the land to be built up to high-tide level and new land is added to the island

107
Q

what do ebb tidal deltas form most commonly

A

high energy environments

108
Q

how do ebb tidal deltas form

A

where they interact with waves and longshore current

109
Q

what are the shoreline features

A
  • spits
  • baymouth bars
  • tombolo
  • tide deltas
  • barrier islands
110
Q

what are barrier islands

A

low ridges of land that PARALLEL the shore and are separated from the shore by lagoons

111
Q

what are barrier islands similar to

A

baymouth bars

112
Q

how are baymouth bars and barrier islands similar

A

a barrier island is what a baymouth bar becomes when it’s more stable and permanent

113
Q

what are barrier island composed of

A

sand, and other materials errored away and brought to that location

114
Q
A

barrier island

115
Q

how are tombolos formed

A

constructive waves and longshore drift

116
Q

describe how tombolos have a buildup of sand

A

based on wave refraction at the island causing currents to converge and influence more deposition of materials

117
Q

describe the entire evolution of a coastline

A

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
Q

what will a shore become if it remains stable

A

a straighter, more regular coast where the headlands have been eroded and bays deposited

119
Q

how to distinguish an old vs young coastline

A

young -
undulating shoreline of headlands and bays and other shoreline features

old-
straighter more regular coastline with bays filled in and headlands erorded

120
Q

what are some factors that influence shoreline erosion

A
  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
Q

how do gentle and steep nearshore slop affect wave feeling bottom

A

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
Q

what are two methods of shoreline stability

A

hard and soft stability

123
Q

what is hard stabilization for shoreline stability

A

any form of ARTIFICIAL structure built to protect a coast or prevent movement of sand along beach

124
Q

what are examples of hard stabilization

A
  • groins
  • jetties
  • seawalls
  • breakwaters
125
Q

jetties vs groins vs breakwaters vs seawalls

A

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
Q

are hard stabilization techniques effective

A

NO

127
Q

soft stabilization alternatives

A
  • beach nourishment
  • relocation
128
Q

what are drawbacks of hard stabilization

A

cost of structures

loss of sand on beach

129
Q

relocation vs beach nourishment

A

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
Q

what are drawbacks of beach nourishment

A
  • 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
Q

2 coastal classifications based on changes in sea level

A

emergent coastlines

submerged coastlines

132
Q

emergent vs submerged coastlines

A

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
Q

which type of coastline is young and which is old

A

emergent coastlines are YOUNG

submerged coastlines are OLD

134
Q

what coastline is an area of erosion

A

emergent coast

135
Q

what shoreline features are on a emergent coast

A

headlands and bays features

136
Q

what coast has newly exposed landscape

A

emergent coast

137
Q

what coast has sunken land

A

submerged coast

138
Q

what coast is an area of deposition

A

submerged coast

139
Q

what features do submerged coast have

A

barrier islands and tombolos

140
Q

what causes tides

A

imbalances between

gravitational force of moon, sun and earth

and centripetal force

141
Q

what are tides

A

the daily changes in elevation of the ocean surface

142
Q

how is gravitational force affected by increasing mass

A

increasing mass increases gravitational force

143
Q

how is gravitational force affected by increased distance

A

increase distance GREATLY DECREASES the gravitational force

144
Q

what do tidal bulges follow

A

the moon as it rotates around the earth (lunar day)

145
Q

why are tides not the same every day

A

based on the lunar day and how it 50 min LONGER than a solar day (24hours)w

146
Q

what’s longer: lunar or solar daya

A

lunar day (by 50 mins)

147
Q

how long is the MONTHLY tidal cycle

A

29 and half days

148
Q

how often does earth alternate between the two tides

A

every 7 days

149
Q

what are the two tides in monthly cycle

A

spring tide vs neap tide

150
Q

spring tide vs neap tide

A

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
Q

what tide has LARGER waves and what have SMALLER waves

A

larger waves = spring tide

neap tide = smaller tides

152
Q

what has more impact of tide sizes moon or sun

A

moon does because despite small size its closer

153
Q

what are three tidal patterns

A

diurnal

semidiurnal

mixed

154
Q

describe the different tidal patterns

A

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
Q

what are tidal bores

A

at the mouth of an estuary where it widens because of tidal movement and the water becomes very intense

156
Q

do most locations have one or two high and low tides per day

A

TWO high and TWO low

157
Q

are two high and two low tides in the same day the same

A

NO - based on declination of moon and sun

Geomorphology (12 decks)

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