OCE1001 chapter 10

Which way would sediment move if NO beach drift existed?

at an angle to shore

How do rip currents form?

Water builds up at the beach face and then moves away from shore in narrow currents.

The Columbia River estuary received its most significant ecological damage from which of the following sources?

hydroelectric dams

In the figure above, showing a hypothetical groin along a coastline. The triangle extending between the groin and the land represents sediment deposited by the longshore current. In what direction is the longshore current moving? Assume up is north.

north

What are submarine canyons?

steep-sided valleys cut into the continental slope

The water level of the eastern Mediterranean Sea is lower than the level at the Strait of Gibraltar due to which of the following?

High evaporation

About what percent of the world fishery is obtained within 320 kilometers (200 miles) of shore?

95%

Sediment is supplied to the coastal zone by:

All of the above are sources of sediment in the coastal zone.

Which of the following can help prevent beach starvation?

Beach replenishment

Which of the following is the largest estuary in the United States?

Chesapeake Bay

An example of a coastal plain estuary is the:

Chesapeake Bay.

Why does the crust subside slightly on either side of a melting glacier?

Crust under the glacier rises as the ice melts. This allows mantle on either side of the glacier to move to areas under the glacier.

Which of the following beach compartment-to-submarine canyon affiliations is incorrect?

Redondo: Mugu

Which of the following statements about wetlands is incorrect?

Wetlands are inefficient at cleansing polluted water.

The coastal wetlands of Louisiana are being lost primarily because of __________.

a combination of subsidence and rising sea level

A beach is:

a deposit of the shore area

How long does it take berms to become narrow and rocky after summer has passed?

a few weeks

In the figure above, which shows an image of waves approaching a shoreline. If you were to go swimming in this location, in which direction would the longshore current push you?

east

An estuary formed from a flooded glacial valley is called a:

fjord

An isothermal temperature profile from surface to seafloor may exist in coastal ocean waters __________.

in either low-latitude waters or high-latitude waters

Eustatic changes in sea level might include:

increased glacial melting due to the global warming.

The particle size on a beach:

is related to whatever material is locally available.

What are groins typically composed of?

large blocks of rock and concrete

An estuary produced by faulting or folding of rocks that creates a dropped-down section into which a river flows is called a:

tectonic estuary.

The part of the shore beyond the low tide breaker line and is deep enough that waves rarely affect the bottom is known as the ________.

offshore

Where does sand accumulate during heavy wave activity?

offshore sand bars

What is longshore transport?

the transport of sand and other sediment in a zigzag pattern down the beach

Geologic evidence suggests that eustatic (global) sea level rises have been caused by __________.

rapid seafloor spreading at divergent plate boundaries

Estuarine circulation associated with a deep, high river volume system where no horizontal salinity gradient exists at the surface is called a:

salt wedge estuary.

Coastal wetlands are characterized by:

high levels of organic matter in the tidal zone and anoxic muds.

Which of the following is designed to prevent or retard shoreline erosion?

All of these are used to try to prevent or retard shoreline erosion.

How is an arch formed along a sea coast?

An arch forms when a sea cave breaks through a headland or where two sea caves coalesce as they erode back due to wave action.

In which area(s) of a barrier island is peat formed?

-low salt marsh -high salt marsh

Which of the following is/are part of a beach compartment?

-submarine canyon -river -beach

Where are barrier islands common?

-Gulf coast of the United States -east coast of the United States

Which of the following statements regarding a highly stratified estuary is/are true?

-Highly stratified estuaries are characterized by a strong halocline. -Highly stratified estuaries are characterized by estuarine circulation, in which river water flows toward the ocean and ocean water flows toward the head of the estuary. -Highly stratified estuaries are common along glaciated or previously glaciated coastlines.

What is the movement of sand down the beach called?

-river -longshore drift -longshore transport

The approximate boundary between salt marshes and mangrove swamps is ________ latitude.

30

About what percent of the world fishery is obtained beyond 320 kilometers (200 miles) of shore?

5%

An estimated ________ of wetlands worldwide have been destroyed in the past century.

50%

The percentage of the original area of wetlands currently left in the United States is approximately:

50%

Of the following statements about coastal wetlands, which is/are true?

ALL, but Salt marshes are a type of coastal wetland found only in the tropics.

How does a sea stack form?

A stack forms when a sea arch collapses, leaving a vertical column of rock offshore.

When less saline water enters a marginal sea above a return flow of saltier water, the circulation pattern is called:

Mediterranean circulation.

Which of the following best describes the coastal ocean environment that results in the temperature versus depth graph shown above?

Middle latitude in winter

In the long term, what do beach drift and longshore current do?

Move sediment parallel to the shoreline

Which of the following occurs during light wave activity?

Much of the swash soaks into the beach

Which of the following statements best describes the seafloor surface in this area?

The seafloor is relatively smooth, and the water is not deep at all.

How does the tide cycle affect erosion along a sea coast?

The tide cycle causes erosion to occur at different elevations along a sea coast.

How is a cave created in a cliff face along a sea coast?

Wave action erodes areas of weakness in rock in a sea cliff.

Reasons for the loss of coastal wetlands include:

all of the above

One major problem associated with the Chesapeake Bay due to increased human pressure is:

an increase in nutrients resulting in more frequent kills of bottom-dwelling or benthic animals.

Important plants in a coastal wetland at 45°N latitude are most likely to be __________.

halophytic grasses and pickleweed

Which of the following processes is responsible for the movement of sand down the beach?

longshore transport

Estuarine circulation associated with a shallow, low-volume estuary in which river water mixes evenly at all depths with ocean water would be called a:

vertically mixed estuary

What is the longshore current?

water forced by waves to move along the shore

The California coast in this region displays a variety of landforms formed by both erosion and sediment deposition. Which term best describes the seafloor structure around placemarks A and B?

wave-cut bench

By looking at the degree of erosion of the platforms, arrange the three platforms (B, D, and F) in order from oldest (formed longest ago) to youngest (formed most recently).

F, D, B

Each of the platforms and the ridges at the placemarks labeled C and E were formed by wave action—the platform at placemark B is currently "under construction," and those at the placemarks labeled D and F are older. What must have happened to produce the three platforms you see here?

The land rose (or sea level dropped) in at least two episodes. First, after the platform (a wave-cut bench) at placemark F was formed, the land rose approximately 130 meters, and the platform at the placemarks labeled D and sea stacks at placemark E were formed. A second uplift of approximately 30 meters left the platform at the placemarks labeled D 30 meters above sea level. The construction of the platform at placemark B began then and continues today.

Features of a depositional coast may include spits, barrier islands, tombolos, and __________.

deltas

Large deposits of sediment at the mouths of rivers are called:

deltas

In the figure above, which shows an image of waves approaching a shoreline. In which overall direction is longshore drift moving the sand along this shoreline?

east

The part of the shore that is exposed at low tide and submerged at high tide is known as the ________.

foreshore

You own a beachfront lot that has been experiencing erosion due to beach starvation. Your neighbor to the north (up-current) has the same problem, so he gets permission to build a groin just north of your property line. Your response would probably be to __________.

get permission to build a groin of your own near the southern boundary of your property

Which of the following describes an estuary located at the mouth of a high-volume river where freshwater flows to the ocean over a layer of dense saline water? Select only one answer.

salt wedge estuary

Which term best describes the landforms at the placemarks labeled C?

sea stacks

Which of the following is an example of hard stabilization?

seawalls

The extent of a continent's coastal waters depends on the size and relief of its continental ________.

shelf

What causes longshore transport?

wave refraction

Which of the following processes is responsible for the graph of salinity versus depth for a coastal ocean?

Fresh water runoff

The part of the shore that extends seaward from the low tide shoreline to the low tide breaker line is known as the ________.

nearshore

Which of the following has caused an increase in the mortality of blue crab, oysters, and other bottom-dwelling animals in Chesapeake Bay since the early 1950s?

Increased discharge of sewage and fertilizers

The Pacific coast, excluding Alaska, has the lowest average erosion rate in the U.S., despite significant beach starvation and localized erosion. Which of the following factors accounts for this low average?

Tectonic emergence

What will happen to the crust as a glacier grows?

The crust under the glacier will sink into the mantle.

How would a beach be affected if a wide berm were protected from erosion during winter months?

The wintertime beach would look similar to the summertime beach.

Which of the following is found at a depositional shore?

deltas

What type of feature is a barrier island?

depositional

In terms of erosion protection from wave action, seawalls:

lead to erosion of sediment on their seaward sides.

The speed of longshore currents decreases as which of the following increases?

wave period

Coastal geostrophic currents are variable because they depend on the ________ and the amount of runoff for their strength.

wind

How are winter beaches different from summer beaches?

Winter waves are short and high, whereas summer waves are long and shallower.

Which of the following statements regarding a salt wedge estuary is/are true?

-Salt wedge estuaries are characterized by a strong halocline. -Salt wedge estuaries are characterized by estuarine circulation, in which river water flows toward the ocean and ocean water flows toward the head of the estuary. -Salt wedge estuaries are common at the mouths of deep, high-volume rivers.

Of the following characteristics or features, which is/are associated with erosional shores?

-Tectonic activity -A coastline with lots of rugged headlands -Wave-cut benches and marine terraces -Rocky coasts

Most waves approach shore at an angle. Why do they break almost parallel to shore?

-The wave bends due to wave refraction. -The part of the wave in shallow water slows down, while the part of the wave in deeper water moves at the same speed. -Waves transition from deep-water waves to shallow-water waves as they approach the shore.

Which of the following estuaries forms when sea level rises and floods an existing river valley?

Coastal Plain Estuary

Of the following characteristics or features, which is/are associated with depositional shores?

ALL, but active tectonic uplift

Which of the following estuaries forms when wave action creates a barrier island that separates the estuary from the ocean?

Bar-Built Estuary

In general, what do beaches look like at the end of winter?

Beaches tend to have a narrow berm and a prominent longshore bar.

What is one of the best ways to recognize a rip current as viewed from above?

Look for turbid water caused by suspended sediment within the rip current.

Why does the crust uplift slightly on either side of a growing glacier?

Mantle under the glacier is pushed aside by sinking crust. This mantle pushes up the crust on either side of the glacier.

Which of the following features is characteristic of an emerging shoreline?

Marine terrace

What process formed the submarine canyons off the Southern California coast?

Some were carved out by rivers when sea level was lower than it is at present, but most form from the erosive action of turbidity currents.

Most marginal seas result from which of the following?

Tectonic events

Let's compare the morphology of the land adjacent to the coastline to what we've observed along the seafloor. Which of the following statements best describes the topography/appearance of the land surface at the placemarks labeled D?

The landscape at the placemarks labeled D is a broad plain, similar to the topography of the seafloor at placemarks A and B.

Which of the following best describes littoral drift?

The movement of sediment in a zigzag fashion caused by the longshore current.

Why does glacial subsidence NOT occur at the exact moment that a glacier forms?

The rate of subsidence is controlled by the rate at which mantle can flow.

Evaluate the ridges at placemark E in the context of what we have explored thus far. Which of the following statements best describes the nature of those ridges?

These small ridges above a plain are similar to the sea stacks present offshore.

How do engineers decrease the amount of erosion caused by a groin?

They build more groins and place them parallel to each other along the beach.

What is an estuary?

a body of water where freshwater and saltwater mix

Of the following types of estuaries, which one has a relatively shallow mouth but is often narrow, long, and extremely deep? Select only one answer.

a drowned glacial valley called a fjord

The section of the coast that extends from normal high tide level to the highest elevation on land that is affected by storm waves is called the:

backshore

In which area of a barrier island would you expect to find a woodland or forest?

barrier flat

If one were to walk from the ocean landward across a barrier island complex, in which order would one encounter the following environments?

beach, dune, barrier flat, high marsh, low marsh

The boundary between the shore and the coast is known as the ________.

coastline

Prevailing offshore winds produce coastal waters that:

have higher salinities.

Southern California beaches in winter typically are narrow and rocky. That is because __________.

heavy winter wave activity moves the sand out to the longshore bar and uncovers the rocks underneath the sand

Which of the following best describes the coastal ocean environment that results in the temperature versus depth graph shown above?

high latitude

Imagine that you are caught in a rip current in the ocean. The best thing for you to do so that you won't drown is to __________.

swim sideways to the current before attempting to come ashore

What is isostasy?

the rising and sinking of Earth's crust relative to the mantle in response to the redistribution of mass on the surface

When seafloor spreading rates increase:

there is a rise in sea level.

For how long will land rebound after a glacier melts?

thousands of years

Which of the following statements is/are true regarding groins?

-Groins are hard-stabilization structures that are always built perpendicular to shore. -Groins slow the movement of sand along the beach. -Groins increase erosion on the downcurrent side.

What happens to a barrier island as sea level rises?

-Peat deposits are exposed on the ocean beach side of the barrier island. -Structures on the island are at risk due to increased erosion.

Which of the following statements regarding a slightly stratified estuary is/are true?

-Salinity lines curve due to the Coriolis effect in a stratified estuary. -Salinity increases from the head to the mouth in a stratified estuary. -Stratified estuaries have a mixed zone.

Which of the following statements regarding a vertically mixed estuary is/are true?

-Salinity lines curve due to the Coriolis effect in a vertically mixed estuary. -River water mixes evenly with ocean water at all depths in a vertically mixed estuary. -Salinity is uniform from the top of the water column to the bottom in a vertically mixed estuary.

In general, what do beaches look like at the end of summer?

Beaches tend to have a wide berm and no longshore bar.