Deck 10: Coasts, Beaches, and Estuaries

Question 1

A low-tide terrace is most likely exposed on a neap tide.

Answer 1

False

Question 2

The net seaward flow of water in a partially mixed estuary is nearly uniform over depth.

Answer 2

False

Question 3

The beach face can have a low region that remains flooded at low tide. This is called a ________.

Answer 3

runnel

Question 4

Tidal currents in an estuary are primarily responsible for mixing.

Question 5

The coastal zone includes both water areas and land areas.

Question 6

A partially mixed estuary generally has a two-layered flow that moves inward at depth and seaward at the surface.

Question 7

Transport of dissolved materials out of an estuary can be estimated from the net T₀ transport and its concentration of dissolves materials.

Question 8

If sea level is to remain constant, the water budget of an estuary requires that all inputs of water equal T_o.

Question 9

An abrupt change in the beach slope caused by the cutting action of waves at normal high tide is known as a beach ________.

Question 10

A drowned river valley is also known as a ________ coast.

Question 11

The beach is the portion of the coastal zone that extends from the low water line to the coastline.

Question 12

Rip currents move water toward the beach.

Question 13

A semienclosed sea at 30°N is most likely resupplied with seawater at depth.

Question 14

Beaches gain sand under severe, high-energy winter waves and lose sand under the milder, low-energy summer waves.

Question 15

Accumulated lag deposits protect a beach from continuing erosion.

Question 16

A coast made regular and linear by wave erosion is a secondary coast.

Question 17

Climate change can result in a worldwide ________ change in sea level.

Question 18

At present, sea level is decreasing around the world's coasts.

Question 19

Primary coasts are coasts that have features created by marine processes.

Question 20

Waves that approach the shore at an angle produce a longshore current that flows parallel to the beach.

Question 21

A beach in dynamic equilibrium

A) loses sand to the offshore area.
B) gains sand.
C) gains and loses sand in equal quantities.
D) builds sand spits and tombolos.
E) gains sand in the low tide terrace.

Question 22

During the last glacial period, sea level was approximately 100 feet lower than today.

Question 23

A beach that is fed by mixed sizes of rocks and particles but shows only large rocks on its surface is ________.

A) an erosional beach
B) subjected to high waves and strong currents
C) an armored beach
D) All of these are correct.
E) None of these is correct.

Question 24

A coast with fjords is classified as a(n) ________.

A) primary coast
B) secondary coast
C) sinking coast
D) rising coast
E) equilibrium coast

Question 25

In an estuary, T_o is always larger than T_i.

Question 26

A sea stack is formed from the deposition of sediment.

Question 27

A coral reef coast is a product of ________.

A) volcanism
B) erosion
C) a change in current direction
D) living organisms
E) wave action

Question 28

A sand spit formed between an offshore island or rock and the mainland is called a(n) ________.

A) offshore spit
B) inshore spit
C) barrier spit
D) sandbar
E) tombolo

Question 29

Sand dunes are found along coasts in which the sand is transported ________.

A) from the beach toward the sea
B) from the beach toward inland areas
C) from inland areas toward the sea
D) from the beach toward inland areas and from inland areas toward the sea
E) from the beach toward the sea, from the beach toward inland areas, and from inland areas toward the sea

Question 30

Pollutants that adhere to suspended particles in an estuary are usually flushed from the estuary by the net circulation.

Question 31

Beaches tend to be wider in winter and narrower in summer.

Question 32

A winter berm tends to be farther inland than a summer berm.

Question 33

A coastal circulation cell includes ________.

A) longshore transport
B) rip currents
C) onshore transport
D) All of these are correct.
E) None of these is correct.

Question 34

An estuary with a short-flushing time will usually have less carrying capacity for pollutants than an estuary with a long-flushing time.

Question 35

Chesapeake Bay is a ________.

A) shallow, well-mixed estuary
B) deep, well-mixed estuary
C) shallow, fjord-type estuary
D) deep, partially mixed estuary
E) salt wedge estuary

Question 36

An example of a ria coast is ________.

A) the mouth of the Mississippi River
B) San Francisco Bay
C) Delaware Bay
D) the Gulf of Mexico
E) southeast Alaska

Question 37

The higher berm found on a beach is formed ________.

A) when large waves occur at low tide
B) during winter storm conditions
C) from the slumping of cliffs in the backshore
D) during periods of low-energy waves in the summer
E) when neap tides occur during the spring and summer

Question 38

High-energy waves of winter storms ________.

A) move sand from bars onto the beach
B) move sand from the beach out to bars
C) build sand spits and tombolos
D) hold sand on the beach and keep the beach stable
E) All of these are correct.

Question 39

A low-tide terrace forms ________.

A) seaward of the offshore bar
B) below the beach face
C) between high and low water
D) along the trough
E) next to the lower beach scarp

Question 40

Barrier Islands are common features along the coasts of the southeast United States.

Question 41

An estuary with strong tidal mixing and low river input is ________.

A) a fjord
B) partially mixed
C) well mixed
D) a salt wedge
E) All of these are correct.

Question 42

The influx of seawater at depth in an estuary ________.

A) supplies water to make up for net surface water outflow
B) supplies salt to compensate for dilution by river water
C) supplies water to maintain the estuary's water level
D) All of these are correct.
E) None of these is correct.

Question 43

If tidal currents are slight in an estuary but river flow is very large, which type of estuary is most likely to occur?

A) a partially mixed estuary
B) a salt wedge estuary
C) a fjord
D) a well-mixed estuary
E) None of these are correct; it is impossible to tell from the information given.

Question 44

In a shallow, well-mixed estuary such as Delaware Bay, the inward transport of salt is controlled by ________.

A) density
B) diffusion
C) advection
D) waves
E) tides

Question 45

An estuary that is found within the mouth of a river where freshwater flows out to sea at the surface while seawater flows upstream along the bottom is ________.

A) a fjord
B) partially mixed
C) well mixed
D) a salt wedge
E) All of these are correct.

Question 46

If the salinity of ocean water at the entrance to an estuary is 30 percent and the average salinity of the estuary is 20 percent, what fraction of the volume of water in the estuary is fresh water?

A) 1/2
B) 1/3
C) 1/4
D) 16
E) 1/8

Question 47

The salt wedge in a river estuary is steeper and more sharply defined during ________.

A) ebb tides
B) flood tides
C) low water
D) high water
E) slack water

Question 48

In a deep fjord with a shallow entrance sill, the deep-basin water is probably ________.

A) low in oxygen and high in nutrients
B) low in salinity and high in oxygen
C) high in oxygen and low in nutrients
D) high in salinity and high in oxygen
E) high in salinity and low in nutrients

Question 49

In a temperate latitude, estuary ________.

A) evaporation exceeds precipitation
B) precipitation exceeds evaporation
C) precipitation equals evaporation
D) winds and tides control the estuary circulation
E) tides only control the estuary circulation

Question 50

The beach face ________.

A) is the same as the low-tide terrace
B) lies under the surf zone
C) is found between high-tide and low-tide levels
D) appears between an offshore bar and a low-tide terrace
E) is found between the summer and the winter berm

Question 51

If S_i is the average salt content of the incoming seawater and S_o is the average salt content of the exiting surface water in an estuary, the fresh water in the exiting mixed water is ________.

A) S_o/(S_i - S_o)
B) S_i/(S_i - S_o)
C) (S_i - S_o)/S_i
D) (S_i - S_o)/S_o
E) (S_o - S_i)(S_i - S_o)

Question 52

If T_o equals the net flow rate of mixed surface water out of an estuary, the estuary volume divided by T_o yields the ________.

A) salt flow
B) water flow
C) flushing time
D) salt residence time
E) freshwater flow

Question 53

If the seawater available to an estuary has a salinity of 30 percent and the seaward-flowing mixed water has a salinity of 20 percent at the estuary entrance, the net volume transport seaward is ________ units per day if the river input is 10 units per day.

A) 5
B) 10
C) 20
D) 30
E) 50

Question 54

A scarp is ________.

A) an underwater sandbar
B) an abrupt change in beach slope
C) a beach fault line
D) the high-water mark on a beach
E) another name for a berm

Question 55

Which combination holds true in a partially mixed estuary?

A) Evaporation - precipitation + runoff = transport in
B) Evaporation - precipitation + runoff = transport in - transport out
C) Transport in - evaporation + precipitation + river runoff = transport out
D) Evaporation - precipitation + runoff = transport in and Evaporation - precipitation + runoff = transport in - transport out
E) Evaporation - precipitation + runoff = transport in - transport out and Transport in - evaporation + precipitation + river runoff = transport out

Question 56

Which of the following coastal engineering structures is built parallel to the shoreline?

A) Jetty
B) Breakwater
C) Groin
D) Seawall
E) None of these is correct.

Question 57

Calculations of flushing times assume that none of the outflowing water is recycled into the estuary. If this assumption is not correct, the actual flushing time is ________ the calculated flushing time.

A) less than
B) greater than
C) the same as
D) not related to
E) None of these is correct.

Question 58

In a well-mixed shallow estuary, the net seaward flow occurs at ________.

A) the surface only
B) depth only
C) middle depths
D) all depths
E) slack water only

Question 59

In a fjord with a shallow entrance sill, the outgoing flow (T_o) is approximately equal to ________.

A) inflow (T_i)
B) freshwater inflow (R)
C) tidal flow
D) estuary volume
E) All of these are correct.

Question 60

In order for an embayment to qualify as an estuary, it must have both ________ and ________.

A) high evaporation; circulation
B) dilution; no physical isolation from the oceans
C) high evaporation; some degree of isolation
D) dilution; some degree of isolation
E) equal evaporation and dilution; no isolation

Question 61

The circulation of water in an inverse estuary is characterized by ________.

A) bottom water flowing in at the surface and seawater flowing out to the sea
B) water flowing into the inverse estuary at all depths
C) bottom water flowing out to the sea and seawater flowing in at the surface
D) water flowing out of the inverse estuary at all depths
E) None of these is correct

Question 62

The backshore ________.

A) is the same as the low-tide terrace
B) lies under the surf zone
C) is found between high- and low-tide levels
D) is part of the foreshore
E) is the high and dry part of the beach

Question 63

In a partially mixed shallow estuary, the net seaward flow occurs at ________.

A) the surface only
B) depth only
C) middle depths
D) all depths
E) slack water only

Question 64

Which type of estuary is characterized by the least variation in salinity with depth at any given point along its axis?

A) a partially mixed estuary
B) a salt wedge estuary
C) a fjord
D) a well-mixed estuary
E) None of these is correct; it is impossible to tell from the information given.

Question 65

Which part of the beach includes the area between the high- and low-tide shorelines?

A) Foreshore
B) Backshore
C) Offshore
D) Coastline
E) Berm

Question 66

Which of the following coastal engineering structures is built perpendicular to the shoreline?

A) artificial dune
B) breakwater
C) groin
D) seawall
E) None of these is correct.

Question 67

If the volume of an estuary is 2.1 km³, and the net flow rate of mixed surface water out of the estuary is 7.5 million m³ per day, the flushing time of the estuary is ________.

A) 1 day
B) 3.5 days
C) 35 days
D) 280 days
E) 350 days

Question 68

If the salinity of ocean water at the entrance to an estuary is 35 and 63 percent of the volume of water in the estuary is ocean water, what is the average salinity of the estuary?

A) 0 percent
B) 13 percent
C) 22 percent
D) 35 percent
E) 63 percent

Question 69

An example of a fault coast is ________.

A) the mouth of the Mississippi River
B) Hanauma Bay, Oahu, Hawaii
C) Delaware Bay
D) the Gulf of Mexico
E) southeast Alaska

Question 70

The low-tide terrace ________.

A) is the same as the backshore
B) lies above the surf zone
C) is found between high- and low-tide levels
D) is part of the foreshore
E) is the high and dry part of the beach

Question 71

Inverse estuaries are generally found between ________.

A) 30°N and 30°S
B) 10°N and 10°S
C) 50°N and 50°S
D) 70°N and 70°S
E) 5°N and 5°S

Question 72

If, in an inverse estuary, the inflow of seawater of 35-percent salinity is 21 units per year and the outflow is 18 units per year, the salinity of outflowing water is ________.

A) 30 percent
B) 35 percent
C) 38 percent
D) 41 percent
E) 65 percent

Question 73

If, in a partially mixed estuary, the seaward flow is 15 units per day and the river input is 11 units per day the net saltwater flow is ________ units per day.

A) 4
B) 8
C) 11
D) 15
E) 26