OCE ch 10

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.

True or False: Erosional coasts are characterized by features of accumulated sand/pebble/rock that are eroded elsewhere and deposited on shore where longshore currents slow.

False

True or False: Longshore drift is a current that transports sand in a circular motion in the water column.

False

True or False: The nearshore is equivalent to the intertidal zone.

False

Which U.S. coastline has the greatest average loss due to erosion?

Gulf coast

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.

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

Move sediment parallel to the shoreline

What would you do to both grow a large beach and protect a harbor mouth?

Place two jetties on either side of the harbor mouth, and build a breakwater upcurrent from the harbor mouth.

How are changes in sea level recorded in rock?

Rock type changes vertically.

How did sea level change to produce this sequence of rocks? [TOP: Limestone, MID1: Mud, MID2: Sand, BOTTOM: Mud]

Sea level fell and then rose.

How did sea level change to produce this sequence of rocks? [TOP: Mud, MID1: Limestone, MID2: Mud, BOTTOM: Limestone]

Sea level fell, then rose, and then fell again.

How did sea level change to produce this sequence of rocks? [TOP: Sand, MID: Mud, BOTTOM: Limestone]

Sea level fell.

How did sea level change to produce this sequence of rocks? [TOP: Limestone, MID: Mud, BOTTOM: Sand]

Sea level rose.

What would you expect to happen to sea level along the Antarctic coastline if the ice cap covering the continent melted?

Sea level would decrease due to isostatic adjustment.

How would you expect sediment to change as you walk from shore into the ocean?

Sediment generally changes from sand to mud to limestone.

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.

True or False: Barrier islands are offshore islands made of sand deposited parallel to the shoreline creating a protective barrier for the coastline.

True

True or False: Elevated wave-cut platforms in southern California are evidence that this coastal area is an emerging shoreline.

True

True or False: Groins are constructed for the purpose of maintaining or widening beaches that are losing sand.

True

True or False: The backshore is found between the normal high tide mark and the coastline.

True

Which feature of barrier islands provides evidence for a rise in sea level?

a peat outcrop

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

deltas

All the following are characteristic of erosional shores except:

deltas.

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

deltas.

The rate of wave erosion along a coastline is determined by all the following except the:

direction of the longshore current.

Emerging shorelines might have all of the following characteristics except:

drowned beaches.

Which of the following pairs does not belong together?

emerging shorelines: drowned beaches

foreshore

exposed at low tide and covered at high tide

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 rock types would you expect to be deposited on top of limestone if sea level rises and then falls?

limestone followed by mud

The "river of sand" described in our text refers to __________.

longshore transport between the beach and the breaker line

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 correct order of beach features as you move from the coast toward offshore is:

berm, beach face, longshore trough, longshore bar

offshore

beyond the low-tide breakers

How do jetties protect harbor entrances?

by inhibiting the deposition of sand in the harbor mouth

All the following are characteristic of depositional shores except :

marine terraces.

Submerging shorelines might have all of the following characteristics except:

marine terraces.

Which rock types would you expect to be deposited on top of limestone if sea level falls and then rises?

mud followed by limestone

In which direction does the longshore current move?

parallel to shore

Which rock types would you expect to see deposited if sea level rises and then falls?

sand covered by mud covered by sand

All the following are alternatives to hard stabilization except :

seawalls.

Isostatic movement of a coastline might occur due to:

the removal of a large glacier that rested in that area.

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

What is the longshore current?

water forced by waves to move along the shore

Of the following statements about beach replenishment, which is/are true?

-Beach replenishment is also known as beach nourishment. -Beach nourishment involves dumping sand on the beach to replace lost sand. -Beach replenishment is expensive because of the huge volume of sand that is necessary to replenish a beach.

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

-High sediment supply -A location near a large delta -Bay-mouth bars -A large sand spit -The formation of barrier islands

Of the following statements about longshore transport (longshore drift), which is/are true?

-Longshore transport moves sediment upcoast or downcoast along the beach. -Longshore transport moves sediment in a zigzag path. -Longshore transport can change direction depending on which direction the waves approach the beach.

Of the following features or conditions, which is/are related to emerging shorelines?

-Lowering of sea level -Tectonic uplift -U.S. West Coast -Marine terraces

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.

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

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

Of the following conditions, which help(s) form a well-developed delta?

-Small wave energy -A large-volume river -High rates of deposition -Low rates of erosion -High sediment load

Which of the following structures are types of coastal stabilization structures?

-breakwaters -jetties -groins

Why are coastal stabilization structures built along coastlines?

-to protect coastal property from wave erosion -to stop beach sand erosion

How does a sea stack form?

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

Of the following statements about coastal regions and landforms, which is/are true?

ALL except: The nearshore is exposed during low tide each day.

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. -seawall -beach nourishment -groin

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

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

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

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

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.

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.

How are winter beaches different from summer beaches?

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

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

What condition would create a weak longshore current?

a wave set approaching parallel to the shore head-on

Which of the following would you expect to find on a summertime beach?

a wide, sandy berm

Winter beaches:

are narrower than summer beaches due to high-energy waves during the winter.

Which way would sediment move if NO beach drift existed?

at an angle to shore

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.