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Geohazard > Coastal Hazards - Depositional and Erosional Coastal Landforms > Flashcards

Coastal Hazards - Depositional and Erosional Coastal Landforms Flashcards

1
Q

Coastlines evolve over time due to the ________ and ________ from breaking waves

A

erosion and deposition ; breaking waves

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2
Q

This interaction between waves and a landmass can cause the shoreline to slowly move landward, a process referred to as _________

A

shoreline retreat

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3
Q

Landward migration of a shoreline can also occur when there is a ____________, or when the land itself becomes ____________

A

rise in sea level ; lower due to subsidence

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4
Q

Accumulations of sediment deposited by waves and longshore currents in the shoreline

A

Beaches

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5
Q

beaches are deposited by:

A

waves and longshore currents

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6
Q

t or f: sediments in beaches are well sorted

A

t

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7
Q

4 main sources for beach sediment:

A
  1. Local cliffs and promontories
  2. The offshore zone
  3. Calcareous sand and shell fragments from coral and mollusc debris
  4. Local river bedload material
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8
Q

are elongate deposits of sediment which parallel the
shore and are separated from the mainland by open water, lagoons, tidal mudflats, or saltwater marshes

A

barrier islands

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9
Q

barrier island are ________ which ________ the shore

A

deposits of sediments ; parallel

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10
Q

barrier islands are separated from the mainland by:

A

open water;
lagoons;
tidal mudflats;
saltwater marshes

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11
Q

are coastal wetlands that form in intertidal areas where sediments have been deposited by tides or rivers

A

tidal flats

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12
Q

is a shallow body of water protected from a larger body of water (usually the ocean) by sandbars, barrier islands, or coral reefs

A

lagoons

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13
Q

Barrier islands result from the complex interaction between _____, _________, and _________

A

waves, sea level change, and sediment supply

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14
Q

how does barrier islands form?

A

wave action causes deposition of sediments offshore forming sand bars, then eventually, enough sand accumulated to form a true island

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15
Q

shoreline retreat is caused by

A

sea level rise and high erosional processes

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16
Q

Tides move sand within inlets in an ________ manner, creating submerged ________ deltas.

A

oscillating manner ; ebb-tide

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17
Q

Long narrow ridges of sand
and shingle which project
from the coastline into the
sea.

A

spit

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18
Q

a beach that is tied to the
coast at one end and free
at the other

A

spit

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19
Q

spit forms ________ to the longshore sediment drift and ____________ to prevailing wind direction

A

parallel ; perpendicular

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20
Q

These are depositional
landforms by which an
island becomes attached to
the mainland by a spit or
bar.

A

tombolo

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21
Q

tombolos are also know as

A

sandy isthmus

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22
Q

how does tombolo form?

A
  1. longshore drift transport material along the coast until the direction changes abruptly or bends
  2. the materials are then deposited in the same direction seawards, forming a spit
  3. the spit continues to grow and joins a nearby offshore island, then a tombolo is formed
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23
Q

These are formed when
sand deposited off the
shore dries out and blown
out to the back of the
beach.

A

coastal dunes

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24
Q

formation of coastal dunes usually need:

A

large tidal range
broad intertidal zones
large supply of sand

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25
Q

Sites of mud and organic deposition, with quiet waters

A

lagoons, mudflats, marshes, and mangrove swamps

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26
Q

t or f: lagoons, mudflats, marshes, and mangrove swamps are enclosed by barriers and spits

A

t

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27
Q

lagoons, mudflats, marshes, and mangrove swamps are formed by combination of _________ and _______

A

river and coastal processes

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28
Q

are wetlands that form as rivers empty their water
and sediment into another body of water, such as an ocean, lake, or another river

A

deltas

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29
Q

t or f: deltas cannot empty into land

A

F (it can but very rare)

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30
Q

Deltas absorb runoff from both ________ and _______

A

floods (river) and storms (oceans, lake)

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31
Q

t or f: Deltas also filter water as it slowly makes its way
through the delta’s distributary network. This can reduce the impact of pollution flowing from upstream

A

t

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32
Q

two major ways to classify a delta:

A
  1. influences/processes
  2. shape
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33
Q

four main types of deltas classified by the processes that control the built-up of silt

A
  1. wave-dominated delta
  2. tide-dominated delta
  3. Gilbert deltas
  4. Estuarine delta
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34
Q

the movement of waves controls a delta’s size and shape

A

wave-dominated delta

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35
Q

usually form in areas with a large tidal range, or area between high tide and low tide.

A

tide-dominated delta

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36
Q

these deltas are formed as rivers deposit large, coarse sediments, are usually confined to rivers emptying into freshwater lakes.

A

Gilbert deltas

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37
Q

form as a river does not empty directly into the ocean, but instead forms a partly enclosed wetland that contains a brackish water habitat.

A

estuarine delta

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38
Q

Deltas with this triangular or fan shape are called ________

A

arcuate (arc-like) deltas

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39
Q

Stronger waves form a _________ , which is more pointed than the arcuate delta, and is tooth shaped.

A

cuspate delta

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40
Q

A _________ has few, widely spaced distributaries, making it look like a bird’s foot.

A

bird-foot delta

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41
Q

The distributary network of an ________ is inland, while a single stream reaches the ocean or other body of water.

A

inverted delta

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42
Q

a type of delta that emptied into a plain, and it extremely rare

A

inland deltas

43
Q

An __________ forms as a river develops a new channel, leaving the other to dry up or stagnate. This process is called _________

A

abandoned delta ; avulsion

44
Q

a natural process by which flow diverts out of an established river channel into a new permanent course on the adjacent floodplain abandoning the former channel.

A

avulsion

45
Q

a rock, sandbar, or other feature lying beneath the
surface of the water

A

reefs

46
Q

reef lie how deep below the surface of water?

A

six fathoms or less beneath low water

47
Q

a fathom is equal to how many feet?

A

6

48
Q

best-known reefs

A

coral reefs

49
Q

coral reefs are developed through _______ processes dominated by _______ and __________

A

biotic ; corals; calcareous algae

50
Q

underwater structures
made from calcium
carbonate secreted by
corals

A

coral reefs

51
Q

coral reefs are often called _____________

A

rainforests of the sea

52
Q

Reefs grow best in _____, ______, _______, _____and _______ waters.

A

shallow, clear, sunny, and agitated waters

53
Q

Most coral reefs were formed after the _________ when melting ice caused the sea level to rise and

A

last glacial period

54
Q

most coral reefs are ___________ years old

A

<10,000

55
Q

Coral reefs are found in the_____ away from
__________, ___________ and as
_________

A

deep sea ; continental shelves; around oceanic islands; atolls

56
Q

vast majority of oceanic islands that form coral reefs around are ________ in orgin

A

vocanic

57
Q

when did Charles Darwin set out his theory about the formation of atoll reefs

A

1842

58
Q

charles darwin theorized that ________ and _______ of the Earth’s crust under the oceans formed atolls

A

uplift and subsidence

59
Q

3 stages of Atoll Formation (Darwin)

A
  1. Fringing Reef
  2. Barrier Reef
  3. Atoll Reef
60
Q

how does atolls form?

A
61
Q

Darwin predicted that underneath each lagoons on atoll reefs would be

A

bed rock base (remains of the original volcano)

62
Q

Where the bottom is rising, fringing reefs can grow around the coast, but coral raised above sea level dies and becomes ________________.

A

white limestone

63
Q

t or f: Barrier reefs and atolls do not usually form complete circles, but are broken in places by storms.

A

t

64
Q

this type of reef is directly attached to a shore, or borders it with an intervening shallow channel or lagoon

A

fringing reef

65
Q

a reef separated from a mainland or island shore by a deep channel or lagoon

A

barrier reef

66
Q

this more or less circular or continuous barrier reef
extends all the way around a lagoon without a central island.

A

atoll reef

67
Q

Marine erosion takes place mainly during
________ and as a result of ________

A

storms ; wave action

68
Q

The repetitive _________ slowly breaks the rocks apart and forms a______________ within the cliff face.

A

hydraulic action ; notch or undercut

69
Q

t or f: As the notch deepens the overhanging cliff becomes less stable, eventually causing the slope to fail in a mass wasting event

A

t

70
Q

In some instances the hydraulic pressure from crashing waves will slowly bore a hole
through a cliff face, forming a____________

A

sea arch

71
Q

are points of land that jut seaward and areas where
waves first make contact with land. This causes waves to refract

A

headlands

72
Q

observed where a more resistant portion
of the rock remains in the surf, separated from the
retreating cliff

A

sea stacks

73
Q

Column of rock standing in the water off a
beach

A

chimney

74
Q

where wave erosion has hollowed out a
line of weakness in otherwise resistant promontory

A

sea arch

75
Q

are places where waves first
make contact with land and with the
greatest amount of energy

A

headlands

76
Q

t or f: in headlands, the energy is high and erosion rate is high

A

t

77
Q

As the waves refract around both sides of the
headlands, eroded material is
transported into ________ via ____________ where it is deposited, forming ___________

A

coves ; longshore current ; isolated beaches

78
Q

how does an active shoreline transitions into a passive shorelines?

A

Once tectonic activity ceases, irregular coastlines slowly evolve into passive shorelines with
more low lying terrain and broad, straight beaches. Initially waves break on headlands, forming
longshore current cells that transport eroded material into coves. As the headlands become
smaller, the beaches and longshore cells will eventually merge, forming relatively straight
sections of beach where sediment is transported parallel to shore.

79
Q

are gently sloping platform of rocks that extend seaward in to a steep drop off.

A

shore platforms

80
Q

what are the dominant influences on coastal landforms?

A
  1. type of continental margin
  2. relief, structure, and lithology
  3. climatic influences
  4. rates of erosion
  5. sea level
81
Q

Edges of actively diverging plates are _________ and ___________, and consequently tend
to be relatively straight with few __________

A

rifted ; block faulted ; embayments

82
Q

what type of continental boundaries forms passive margins with continental shelves?

A

Divergent boundaries

83
Q

t or f: passive continental margins have thicker sedimentary carapce

A

t

84
Q

active continental margin is also called

A

Pacific Type Boundary

85
Q

pacific type boundaries are characterized by islands such as

A

Philippines, Indonesia, and Japan

86
Q

t or f: pacific type boundaries exhibit continental shelves

A

F (absent and continental shelf)

87
Q

in pacific type boundary, structural trend_____________ to the line of convergence

A

parallel

88
Q

t or f: pacific type boundary have deep offshore trenches and a line of a mountainous arc

A

t

89
Q

passive continental margin is also called

A

Atlantic-type Margins

90
Q

atlantic-type margins may have _______ and ______ continental shelves

A

shallow and broad

91
Q

Resistant rocks and or tectonically uplifted
blocks form_________with ____________

A

uplands ; cliffed coastal margins

92
Q

competent rocks have _________ relief

A

high

93
Q

soft rocks exhibit ________ relief

A

low

94
Q

The energy available for coastal processes is partially controlled by

A
  1. wave height
  2. wind speed direction
  3. wind speed duration
95
Q

High energy coasts tend to have ____________, _____________

A

rocky beaches ; severely eroded upland coasts

96
Q

Low energy coasts tend to have _________, _______, or ______

A

deltas, salt marshes, mangrove swamps

97
Q

coasts between latitudes of ____________ and _______ facing coasts in the ______________ generally have high storm induced _________

A

45 to 60 degrees ; east; tradewind belts; swells

98
Q

energy along waves is influenced by

A

wind

99
Q

t or f: high winds = greater wave heights

A

t

100
Q

t or f: coastal zone is a rapid zone of change

A

t

101
Q

t or f: coasts may advance or retreat in a yearly basis

A

t

102
Q

Coastal positions have changed almost constantly through constant cycle of __________ and _____________

A

glaciation and melting

103
Q

Present day sea levels can be related into an environment of _______

A

warm period

Geohazard (25 decks)

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