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Chapter 20 Shorelines
Earth: An Introduction to Physical Geology 20.1
Multiple-Choice Questions1)
Fetch refers to ________. A)
a large expanse of open water over which the wind blows and generates waves B)
ocean currents moving parallel to the beach C)
the rotational movements of water particles beneath a passing, surface wave D)
the beachfront area where rapid erosion is taking place Answer :
A
2)
A deep-water wave exists when ________. A)
the wavelength exceeds one-half the water depth B)
the wavelength exceeds one-half the wave height C)
the water depth exceeds one-half the wavelength D)
the wave height exceeds the water depth Answer :
C
3)
Water movement and sand transport parallel to the beach are fundamentally caused by ________.
A)
strong, offshore winds creating a pileup of water along the beach front B)
deep-water waves breaking offshore C)
waves impinging obliquely onto a beach D)
a long fetch parallel to the beach Answer :
C
4)
Swash and backwash describe ________. A)
movements of water and sand as waves break along a beach B)
the oscillatory movement of water beneath a passing wave C)
the swirling action and sand movements produced when a shallow water wave impinges on the bottom
D)
the forward and backward water movements as storm waves reflect from a seawall or groin Answer :
A
5)
How does refraction affect the crest and trough orientations of incoming waves along a beach?
A)
as the waves move into shallower water, the angle between the wave crests (troughs) and the shoreline increases
B)
as the waves move into shallower water, the angle between the wave crests (troughs) and the shoreline decreases
Answer :
B
6)
________ are built more or less parallel to the beach. A)
Jetties B)
Seawalls C)
Groins D)
Breakers Answer :
B
7)
Over the past few thousand years, how, if at all, has sea level been changing? A)
It has fallen about 10 inches per century. B)
It has risen about 10 centimeters per century. C)
It has remained about the same. D)
none of the above Answer :
B
8)
How can crashing, collapsing, storm waves generate explosive forces and stresses on rocky outcrops and manmade structures?
A)
pressurized water and compressed air are driven into cracks and fissures B)
backwash breaks out blocks of rock or concrete and carries them out to deeper water C)
oscillating, refractive waves shake the hard materials into small fragments D)
all of the above Answer :
A
9)
Increasing quantities of ________ will eventually produce global warming. A)
carbon dioxide B)
ozone C)
water vapor D)
volcanic aerosols Answer :
A
10)
Erosional retreat of a ________ leads to enlargement and extension of a wave-cut platform in the inland direction.
A)
wave-cut cliff B)
wave-cut barrier beach C)
wave-cut tombolo D)
offshore, wave-cut, breakwater bar Answer :
A
11)
How are spits, hooks, and baymouth bars formed? A)
A headland is eroded and the sand is deposited in an offshore basin. B)
Wave erosion cuts away both sides of a long sand bar, leaving a sand ridge aligned parallel to the shore.
C)
Sand is deposited from longshore currents. D)
Sand eroded from a wave-cut diff is deposited around sea stacks and arches. Answer :
C
12)
Which one of the following coastlines would typically have wave-cut cliffs, sea stacks, sea arches, and wave-cut platforms?
A)
one where bedrock is vigorously eroded as sea level rises B)
one where a bedrock, wave-cut cliff is rapidly retreating inland as sea level falls C)
one where unconsolidated sediments are being eroded as sea level falls D)
one where unconsolidated sediments are being rapidly eroded as sea level rises Answer :
A
13)
Emergent coastlines of Scandinavia (Norway and Sweden) and the Hudson Bay region of Canada result from which one of the following combinations?
A)
the rate of glacial rebound exceeds the rate of sea level rise B)
the tectonic subsidence rate exceeds the rate of sea level rise C)
the rate of glacial rebound is less than the rate of sea level rise D)
the rate of tectonic uplift exceeds the rate of sea level fall Answer :
A
14)
Large estuaries are more common on a ________ coastline. A)
submergent B)
retreating C)
stable D)
emergent Answer :
A
15)
A ________ tide is an incoming or rising tide. A)
drift B)
flood C)
ebb D)
rip Answer :
B
16)
________ are the maximum-amplitude tides produced when the Sun, Earth, and Moon are aligned.
A)
Rip tides B)
Spring tides C)
Surf tides D)
Neap tides Answer :
B
17)
Which of the following is true regarding the gravitational forces affecting Earth? A)
The lunar force is about twice that of the Sun. B)
The solar and lunar gravitational forces are about the same magnitude. C)
The solar force is about twice that of the Moon. D)
The gravitational forces of each vary depending upon seasons on Earth. Answer :
A
18)
Which of the following statements concerning the Mississippi delta lands is not true? A)
Coastal erosion and loss of delta lands will continue as sea level continues to rise. B)
Artificial levees help spread river-borne sediment uniformly over the delta swamps and wetlands.
C)
The sediment supply has dropped since large reservoirs were constructed on the Missouri and Arkansas Rivers.
D)
The thick sediment pile is slowly compacting and the delta is slowly subsiding. Answer :
B
19)
________ refers to the broad dome of water moving with the eye and frontal portion of a hurricane.
A)
Cyclonic mound B)
Storm surge C)
Eyewall ridge D)
Sea dome Answer :
B
Match the policy options with expected costs and long-term effectiveness, assuming that sea level will continue to slowly rise in the future.
A. promote coastal development; build massive, hardened structures to stop all but the most powerful storm wavesB. prohibits coastal development; build nothing, declare victory over the sea and retreat from the coastlineC. allow coastal development; make a long-term commitment to beach nourishment
20)
________ low initial costs and modest maintenance costs; high potential for storm damages and low to moderate potential for negative environmental effects
Answer :
C
21)
________ high initial costs and eventually high maintenance costs; high potential for storm damage and negative environmental consequences
Answer :
A
22)
________ low initial costs and low maintenance costs; low potential for storm damages and for negative environmental consequences
Answer :
B
23)
________ is not a dynamic characteristic of a wave of oscillation. A)
Fetch B)
Velocity or speed C)
Wavelength D)
Period Answer :
A
24)
________ are currents that move sand and water parallel to the beach. A)
Reflected B)
Longshore C)
Translational D)
Ebb tide Answer :
B
25)
When does a deep-water wave change to a shallow water wave? A)
only when the wave period is greater than one-half the water depth B)
only when the wavelength is about twice the water depth C)
only when the wavelength is about one-half the water depth D)
only when the wave period is greater than twice the water depth Answer :
B
26)
Incoming waves slow down and rotate towards an orientation of being parallel to the shoreline. This process is known as ________.
A)
reflection B)
relaxing C)
refluxing D)
refraction Answer :
D
27)
Which one of the following would prove that a coastline was emergent? A)
elevated, wave-cut terraces B)
many small bedrock islands C)
extensive barrier islands D)
numerous large estuaries Answer :
A
28)
Which one of the following is an artificial coastal feature? A)
breakwater B)
sand spit C)
sea arch D)
barrier island Answer :
A
29)
________ refers to the movements of sand and water on a beach due to a breaking wave. A)
Swash and slosh B)
Backwash and swash C)
Slash and slosh D)
Wash and backslosh Answer :
B
30)
A ________ is an isolated remnant of bedrock standing above a wave-cut platform. A)
sea stack B)
sea span C)
sea rampart D)
sea spit Answer :
A
31)
A ________ extends partway across the mouth of a bay or estuary. A)
barrier island B)
spit C)
jetty D)
sand arch Answer :
B
32)
A baymouth bar is ________. A)
a sand deposit on the seaward side of a tidal inlet to a large estuary B)
a sand bar extending across the former inlet to a bay or estuary C)
a sand barrier extending partway across the entrance to a bay or estuary D)
a sand deposit on the estuary side of an inlet through a barrier island Answer :
B
33)
A ________ migrates inland as a wave-cut platform is extended. A)
wave-cut barrier dune B)
wave-cut barrier stack C)
wave-cut arch D)
wave-cut cliff Answer :
D
34)
Which one of the following would not be a likely effect of a breakwater? A)
increased, longshore current velocities between the breakwater and the beach B)
dissipation of storm wave energy on the seaward side of the breakwater C)
increased sand deposition between the beach and the breakwater D)
increased erosion of the beach on one side of the breakwater Answer :
A
35)
A natural sand bar or low, sand ridge that connects one island to another island or to the mainland is called a ________.
A)
sand groin B)
spit C)
jetty barrier D)
tombolo Answer :
D
36)
Which one of the following is not directly related to wave refraction? A)
Speeds decrease as waves enter shallow water. B)
Ebb tidal currents carry large quantities of sand from estuaries to the seacoast side of a barrier island system.
C)
Deposition is concentrated in bays and protected waters. D)
Erosional energy is focused on headland areas along the beach. Answer :
B
37)
________ not the direct result of longshore current action. A)
Building and extension of spits are B)
Closing off of small estuaries by baymouth bars is C)
Transport of sand along the beach is D)
Cracking and abrasion of rock at the base of a wave-cut cliff are Answer :
D
38)
A ________ tide is a tidal current flowing through an inlet into a bay or estuary. A)
forward B)
spring C)
flood D)
ebb Answer :
C
39)
________ are coastal structures designed to keep tidal inlets from shifting location or filling with sand.
A)
Breakwaters B)
Seawalls C)
Jetties D)
Groins Answer :
C
40)
Which one of the following statements concerning sea level is correct? A)
It has dropped since 900 A.D., but will probably rise for the next few hundred years. B)
It dropped during the past few centuries and that trend will continue. C)
It rose over past centuries but will probably drop in the next hundred years. D)
It rose for the past few centuries and will continue to rise. Answer :
D
Match the coastline type with the appropriate description or location.
A. emergent B. submergent
41)
________ Chesapeake and Delaware Bays and the North Carolina Sounds Answer :
B
42)
________ large areas of coastal swamplands, large estuaries, and barrier islands Answer :
B
43)
________ wave-cut (eroded) cliff, sea stacks, and elevated wave-cut terraces Answer :
A
44)
Which of the following correctly describes a fiord (fjord)? A)
deep stream-cut canyon flooded as the coastal lands subsided during the last one million years
B)
deep, glacier-cut valley flooded as the coastal lands subsided during the last one million years
C)
deep, glacier-cut valley flooded by rising sea level over the last 10,000 years D)
deep stream-cut canyon flooded by rising sea level over the last 10,000 years Answer :
C
Match the tide with the appropriate description.
A. neap tides B. spring tides
45)
________ Sun, Moon, and Earth form a right triangle in space Answer :
A
46)
________ lowest high tides and highest low tides of the month Answer :
A
47)
________ highest high tides and lowest low tides of the month Answer :
B
48)
________ Sun, Moon, and Earth lie on a straight line in space Answer :
B
20.2
Word Analysis QuestionsExamine the words and/or phrases for each question below and determine the relationship among the majority of words/phrases. Choose the option which does not fit the pattern.
1)
A) berm B) shoreline C) beach face D) beach Answer :
shoreline
2)
A) wave height B) wave period C) wave refraction D) fetch Answer :
wave refraction
3)
A) wave-cut cliff B) wave-cut platform C) sea arch D) spit Answer :
wave-cut platform
4)
A) sea stack B) bar C) tombolo D) barrier island Answer :
sea stack
5)
A) jetties B) groin C) seawall D) beach nourishment Answer :
jetties
20.3
True/False Questions1)
The wave period is the horizontal distance between neighboring crests or troughs of a wave.
Answer :
FALSE
2)
Tidal flats are mostly submerged during ebb tides. Answer :
FALSE
3)
As waves move into the beach area, they change to waves of translation. Answer :
TRUE
4)
Sea level has been slowly rising since the last Pleistocene ice sheets melted away. Answer :
TRUE
5)
A baymouth bar is a manmade feature designed to stop incoming storm waves before they impact on the beach.
Answer :
FALSE
6)
The effect of the Sun on tides is about one-half that of the Moon. Answer :
TRUE
7)
Because the land is rising faster than sea level, storm damage and erosion along emergent coastlines are relatively unimportant.
Answer :
FALSE
8)
Massive seawalls and groins, financed by the average taxpayer, are very cost-effective methods for protecting expensive, privately owned, beach front properties.
Answer :
FALSE
9)
Deep water waves in the open sea are waves of oscillation. Answer :
TRUE
10)
Elevated, wave-cut platforms are good evidence for an emergent coastline. Answer :
TRUE
11)
Barrier islands are quite rare along the Gulf of Mexico coastline. Answer :
FALSE
12)
The rocky Maine coastline is emergent because the land is rising faster than sea level. Answer :
FALSE
13)
Groins are constructed perpendicular to the beach; they are designed to trap sand that might otherwise keep moving along the beach.
Answer :
TRUE
14)
Barrier islands are more common along the Pacific coast of the United States than along the Atlantic coast.
Answer :
FALSE
15)
Over the past few centuries, sea level has been gradually falling. Answer :
FALSE
16)
Spring tides refer to the largest, daily, astronomical tidal range during any month. Answer :
TRUE
17)
Neap tides are produced when the Earth, Sun, and Moon are positioned to form a right triangle in space.
Answer :
TRUE
18)
Water flows into bays, sounds, and estuaries on a flood tide. Answer :
TRUE
19)
Carbon dioxide is the main atmospheric gas associated with the greenhouse effect. Answer :
TRUE
20)
Longshore sand transport and longshore currents depend on waves impinging parallel to a shoreline.
Answer :
FALSE
21)
On submergent coasts with large estuaries and coastal swamps, rivers and streams carry large quantities of sand directly to the beaches and barrier islands.
Answer :
FALSE
22)
Fjords are broad, shallow, coastal stream valleys that emerged from the sea as the coastal bedrock rebounded after the ice melted away.
Answer :
FALSE
23)
Delta lands will decrease in area if upstream dams trap sediment, preventing it from reaching the delta and channelized distributaries which carry sediments directly to deeper offshore waters.
Answer :
TRUE
20.4
Short Answer Questions1)
As a deep-water wave enters shallow water, the wave slows down and rotates toward being parallel with the shoreline. This process is known as ________.
Answer :
refraction
2)
________ currents refer to water moving parallel to a shoreline. Answer :
Longshore
3)
________ are long, narrow, offshore, sand ridges between an estuary and the open ocean are common along the Atlantic and Gulf of Mexico coasts.
Answer :
Barrier islands
4)
A ________ is a low, sand ridge connecting an offshore island with the mainland or with another island nearer to the mainland.
Answer :
tombolo
5)
A ________ is a structure, built parallel to the shoreline to dissipate much of the energy from incoming waves.
Answer :
breakwater
6)
A ________ is a manmade structure, extending at right angles to the beach, built to trap sand moving parallel to the beach.
Answer :
groin
7)
What two terms denote the complex water and sand movements associated with a wave breaking on a beach?
Answer :
swash, backwash
8)
What term denotes a sand bar built across the former mouth of an estuary, separating it from the open sea?
Answer :
baymouth bar
9)
Falling tides and tidal currents flowing from an estuary to the open sea are known as ________.
Answer :
ebb tides
10)
A ________ is a high rocky pinnacle that rises from a wave-cut platform. Answer :
sea stack
20.5
Critical Thinking QuestionsUse complete sentences, correct spelling, and the information presented in Chapter 20 to answer the questions below.
1)
Shorelines are temporary geologic and topographic features. Explain this statement.
2)
Briefly discuss the movement of sand on a beach environment. Include those factors, both natural and human-induced, that affect sand movement.
3)
A variety of techniques and efforts are used to stabilize shorelines throughout the world. Are all of these efforts only temporary measures or are any of them permanent? Also, does urbanization and development of coastal areas always contribute to shoreline erosion? Explain.
20.6
Visualization Questions1)
Label the basic parts of a wave on the diagram below.
Answer :
See figure 20.3 in chapter 20 of Earth, 9e
2)
What type of current is illustrated in the diagram below?
Answer :
See figure 20.10 in chapter 20 of Earth, 9e
3)
Match the features on the illustration below with the correct answer for each one.
A) tombolo B) wave-cut cliff C) spit D) baymouth bar
Answer :
a) D b) B c) A d) C
4)
Carefully examine the illustration below.
What name is given to walls like the wall above that is labeled A? a) ________What name is given to walls like the wall above that is labeled B? b) ________What name is given to walls like the wall above that is labeled C? c) ________In the future, what will eventually happen to the beach at the following locations?Location G d) ________ Location F e) ________Location E f) ________ Location D g) ________
Answer :
a) groins b) breakwaters c) jettiesd) It will widen as more sand accumulatese) It will widen as more sand accumulatesf) It will narrow as sand is removedg) It will widen as more sand accumulates
5)
Label the tidal flat, tidal delta, and barrier island on the diagram below.
Answer :
See figure 20.30 in chapter 20 of Earth, 9e