Deck 11: The Ocean Floor

Question 1

With respect to constructing seashore buildings or foreshore engineering works, the best advice should be: .

A) Fight for publicly funded maintenance and insurance programs to protect your private investments.
B) Don't worry mon, be happy.
C) Don't build resorts or houses but seawalls and port facilities can be made strong enough.
D) Builder beware; if you treat this as an unchanging setting, you will put yourself and your resources in conflict with awesome forces of nature.

Answer 1

D

Question 2

Which one of the following is not directly related to wave refraction?

A) Deposition is concentrated in bays and protected estuaries.
B) Ebb tidal currents carry large quantities of sand from estuaries to the seaward side of a barrier island system.
C) Erosional energy is focused on headland areas protruding from the beach.
D) Wave speeds decrease as waves enter shallow water.

Answer 2

B

Question 3

is not a dynamic characteristic of a wave.

A) Velocity or speed
B) Period
C) Wavelength
D) Fetch

Answer 3

D

Question 4

Erosional retreat of a(n) leads to enlargement and inland extension of a wave- cut platform.

A) wave- cut tombolo
B) offshore, wave- cut, breakwater bar
C) wave- cut barrier beach
D) wave- cut cliff

Question 5

How much pressure can be exerted by those "perfect waves" that characterize the North Atlantic winter storms?

A) 1,000,000 kg/m2
B) 1 kg/m2
C) 10,000 kg/m2
D) 100 kg/m2

Question 6

The shorelines are .

A) dynamic landscape features balanced between erosion and deposition, by wind and waves
B) principally molded by intermittent geologic cataclysms like earthquakes, landslides, tsunamis, and volcanic eruptions
C) ancient geologic oddities, shaped long ago by continent and ocean geometries
D) constant features determined only by sea level and elevation

Question 7

Relative to shoreline, provided sea level , irregularities along a coast can be gradually smoothed out by the combined processes of erosion and deposition.

A) gradually rises
B) remains stable
C) gradually falls
D) rapidly falls

Question 8

Incoming waves slow down and rotate toward an orientation of being parallel to the shoreline. This process is known as .

A) refluxing
B) reflection
C) relaxing
D) refraction

Question 9

Much of the sediment deposited in the underwater portion of the coastal profile is caused by

A) longshore currents
B) storms
C) rip currents
D) tidal deltas

Question 10

What is the seaward limit of the offshore zone?

A) fair weather wave base
B) the sea arch
C) the barrier island
D) the beach berm

Question 11

are constructed parallel to the shoreline and designed to reflect wave energy out to sea.

A) Seawalls and breakwaters
B) Tidal deltas
C) Barrier islands
D) Groins and jetties

Question 12

When does a deep- water wave change to a shallow water wave?

A) only when the wave period is greater than twice the water depth
B) only when the wavelength is about one- half the water depth
C) only when the wave period is greater than one- half the water depth
D) only when the wavelength is about twice the water depth

Question 13

The net longshore movement of water, and transport of sand parallel to the beach, are fundamentally caused by .

A) deep- water waves breaking in the nearby offshore region creating rips
B) offshore winds creating a pileup of water and a stronger backwash than swash
C) a long fetch parallel to the beach
D) waves refracting and breaking obliquely onto a beach

Question 14

Increasing quantities of in the atmosphere correlated to 0.6° C increase in mean annual temperature during the 20th century and could produce considerably greater global warming.

A) volcanic aerosols
B) carbon dioxide
C) nitrous and sulphur oxides
D) ozone

Question 15

Where is wave attack the strongest?

A) on the crest of the beach berm
B) in mid ocean before waves shoal and slow down
C) in the unprotected middle of bays and estuaries
D) against the sides and ends of headlands

Question 16

Which one of the following coastlines would typically have bedrock features such as wave- cut cliffs, sea stacks, sea arches, and wave- cut platforms?

A) one where a bedrock wave- cut cliff is rapidly retreating inland as sea level falls
B) one where unconsolidated sediments are being eroded as sea level falls
C) one where unconsolidated sediments are being rapidly deposited as sea level rises
D) one where bedrock is vigorously eroded in the surf zone as sea level rises

Question 17

A(n) current forms during an incoming or rising tide.

A) ebb
B) flood
C) rip
D) drift

Question 18

Which of the following is true regarding the gravitational forces affecting Earth?

A) The solar attraction is about twice that of the Moon.
B) The solar and lunar gravitational attractive forces are about the same magnitude.
C) The gravitational forces of each vary depending upon seasons on Earth.
D) The lunar attraction is slightly more than twice that of the Sun.

Question 19

Where is the world's greatest tidal range?

A) The Coast of Brittany in France
B) Belize in the tropics
C) Greenland's north coast
D) Minas Basin, Bay of Fundy, Nova Scotia

Question 20

How great can the speed of tidal currents be, such as during spring tides off the coast of Brittany in France?

A) 100 km/hr
B) 20 km/hr
C) 10 km/hr
D) 2 km/hr

Question 21

A natural sand bar or sand/gravel ridge exposed at low tide that connects one island to another island, or an island to the mainland, is called a .

A) jetty barrier
B) sand groin
C) spit
D) tombolo

Question 22

High initial costs and eventually high maintenance costs, high potential for storm damage and negative environmental impact are consequences of policies to .

A) allow coastal development, make a long- term commitment to beach nourishment
B) prohibit coastal development, build nothing but grass shacks, put a moratorium on insurance, declare victory over the sea, and retreat from the coastline
C) promote coastal development, build massive, hardened structures to stop all but the most powerful storm waves
D) get wasted in Margaritaville!

Question 23

Low initial costs and low maintenance costs, low potential for storm damages, and low negative environmental impact are consequences of policies to .

A) prohibit coastal development, build nothing but grass shacks, put a moratorium on insurance, declare victory over the sea, and retreat from the coastline
B) fly to Tahiti
C) allow coastal development, make a long- term commitment to beach nourishment
D) promote coastal development, build massive, hardened structures to stop all but the most powerful storm waves

Question 24

How, if at all, did sea level change at the end of the Pleistocene Epoch?

A) It rose about 100 metres during the recession of the last ice sheets.
B) It has fallen about 10 cm per century due to human use of water for irrigation.
C) It has remained about the same.
D) It rose and drowned the ancient city of Atlantis.

Question 25

How much has global sea level risen in the past century from global warming and melting of ice caps?

A) up to 25 cm
B) 2.5 cm
C) 25 m
D) 2.5 m

Question 26

What causes the pair of tidal bulges?

A) The larger one closest to the Moon is gravitational; 180° away it is inertial.
B) The east and west shores of the Americas pushing the water out of the way like giant mixer blades.
C) One is caused by the pull of the moon, the other by the sun.
D) The shape of the whole Earth gets deformed into a flattened ellipsoid by the Moon's gravity; the other bulge is due to centrifugal force bending the rocks back but delayed by a quarter revolution.

Question 27

currents move sand and water parallel to the beach.

A) Reflected
B) Longshore
C) Ebb tide
D) Translational

Question 28

A extends partway across the mouth of a bay or estuary.

A) sand tongue
B) jetty
C) spit
D) barrier island

Question 29

Where is Canada's greatest tidal range?

A) The Gulf of St. Lawrence along the eastern townships of Quebec
B) Minas Basin, Bay of Fundy, Nova Scotia
C) Hudson Bay near Moose Factory Ontario
D) Richards Island, NWT along the western Arctic shore

Question 30

Associated with gaps in a barrier island, a tidal delta is deposited .

A) by major sand movements during neap tides
B) on the seaward side of a tidal inlet
C) on the estuarine side of a tidal inlet
D) in the water gap following stream piracy

Question 31

What does the following sequence signify? Mud overlain by hummocky, crossbedded sand overlain by swaley, crossbedded sand overlain by parallel, tabular bedded, laminated sand overlain by sand with large scale crossbedding.

A) rising sea level with a nearby glacial advance
B) erosional or retreating shoreline at constant sea level
C) rising sea level or migration of a delta away from the area
D) falling sea level or buildup of a sandy shore into deeper water

Question 32

not the direct result of prevailing longshore current action.

A) Fracturing, shattering, and abrasion of rock at the base of a wave- cut cliff are
B) Transport of sand along the beach is
C) Building and extension of spits are
D) Closing off of small estuaries by baymouth bars is

Question 33

Which one of the following is an artificial (manmade) feature constructed parallel to the shore?

A) sand spit
B) sea arch
C) breakwater
D) barrier island

Question 34

A(n) current is a tidal current advancing into a shallow coastal zone, as it flows through a strait or inlet into a bay or estuary.

A) ebb
B) flood
C) forward
D) spring

Question 35

How thick are the storm- deposited, swaley, cross- stratified sand deposits that tend to be preserved in the lower shoreface?

A) 20- 35 m
B) 50- 125 m
C) <2 m
D) 2- 15 m

Question 36

The foreshore zone is .

A) found in estuaries behind barrier islands
B) landward of stabilized dunes with permanent vegetation
C) where the swash and backwash dominate between the low- tide and high- tide zones
D) the stable part of the beach above the high- tide zone

Question 37

are generally built in pairs to preserve the location of a river mouth or harbour entrance.

A) Caissons
B) Jetties
C) Groins
D) Seawalls

Question 38

How does refraction affect the shape of incoming waves along a beach?

A) As the waves move into shallower water, the wave loses energy to the seabed, decreasing the wave height.
B) As the waves move into shallower water, the angle between the wave crests (troughs) and the shoreline increases.
C) As the waves move into shallower water, the wave slows down and the crests spread farther apart.
D) As the waves move into shallower water, the angle between the wave crests (troughs) and the shoreline decreases.

Question 39

What is the path followed by a sand grain from a succession of waves impinging obliquely onto a beach?

A) A sawtooth path, driven obliquely up the beach face with the swash then straight down the beach face with the backwash.
B) Perpendicular to the wave front, obliquely up the beach on the swash, then reflected out at an opposite but equal angle with the backwash.
C) A path parallel to the beach, but well offshore as sand is only moved by longshore currents not by breaking waves.
D) A straight path, right at the shoreface, pushed along parallel to the beach by the breaking wave.

Question 40

Where does most active sediment transport occur?

A) in the longshoreman's zone by stevedores
B) on the beach face by winds
C) in the shoreface zone by breaking waves and longshore currents
D) the offshore zone by pelagic currents

Question 41

The backshore zone is .

A) landward of stabilized dunes with permanent vegetation
B) where the swash and backwash dominate between the low- tide and high- tide zones
C) found in estuaries behind barrier islands
D) the stable part of the beach above the high- tide zone

Question 42

What facies of sand deposits typically display millimetre- scale beds with gentle seaward dips and parallel lamination defined by alternating layers of clean white quartz and darker heavy mineral concentrates?

A) lagoon deposits
B) swaley, lower shoreface deposits
C) alternating bedded offshore deposits
D) lower beachface/foreshore deposits

Question 43

is an economically viable long- range solution to beach preservation only where there is dense development, large supplies of sand, low wave energy, and reconcilable environmental issues.

A) Beach nourishment
B) Abandonment and relocation
C) Foreshore garbage dumping
D) Breakwater and seawall construction

Question 44

Low initial costs and modest maintenance costs, high potential for storm damage and low to moderate potential for negative environmental effects are consequences of policies to .

A) promote coastal development, build massive, hardened structures to stop all but the most powerful storm waves
B) prohibit coastal development, build nothing but grass shacks, put a moratorium on insurance, declare victory over the sea, and retreat from the coastline
C) allow coastal development, make a long- term commitment to beach nourishment
D) don't worry mon, be happy!

Question 45

How can crashing, collapsing, storm waves generate explosive forces and stresses on rocky outcrops and manmade structures?

A) Oscillating, refractive waves shake the hard materials into small fragments.
B) Storm waves hurl big rocks up into the suspended load, hammering the shore.
C) Backwash breaks out blocks of rock or concrete and carries them to deeper water.
D) The weight, momentum, and pressure of storm waves compresses air into cracks, shattering rock.

Question 46

are built more or less parallel to the beach.

A) Jetties
B) Seawalls
C) Groins
D) Caissons

Question 47

How are spits and baymouth bars formed?

A) Sand is transported by longshore currents and deposited where energy decreases.
B) A headland is eroded and the sand is deposited in an offshore basin.
C) Wave erosion cuts away both sides of a long sand bar, leaving a sand ridge aligned parallel to the shore.
D) Sand eroded from a wave- cut cliff is deposited around sea stacks and arches.

Question 48

Which active landform is most common along the Texas- Gulf of Mexico coast?

A) sombreros
B) barrier islands
C) sea stacks
D) deltas

Question 49

directly generates the major surface currents in the world's oceans.

A) Wind
B) Longshore drift
C) Seafloor spreading
D) Gravity of the Sun and Moon

Question 50

What is the cause for the present day rise in sea level of 2.0- 2.5 mm/year?

A) Global warming, due to the combustion of fossil fuel, is melting the ice caps and expanding the ocean volume.
B) Increasing mid- ocean ridge volume is accelerating seafloor spreading.
C) Tectonic forces are buckling the seafloor all around the Pacific.
D) Increased flatulence by cattle that are being bred in record numbers for hamburgers.

Question 51

What current geologic processes ultimately doom any attempts to stabilize and preserve shorelines within a century or so?

A) global plate motions and tectonic shifts
B) gradual sea level rise of 1- 2 mm/year related to global warming
C) loss of river discharge from dams and water use on most major rivers
D) increasing storm severity

Question 52

Swash and backwash describe .

A) the onshore and offshore movement of water relative to the beach by turbulent surf
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 an shallow offshore bar
D) the forward and backward water movements as storm waves reflect from a seawall or groin

Question 53

Longshore currents and sediment transport result from which situation?

A) Incoming wave crests are perpendicular to the shoreline.
B) Incoming wave crests are slightly oblique to the shoreline.
C) Incoming wave crests are non- existent.
D) Incoming wave crests are parallel to the shoreline.

Question 54

Which one of the following would not be a likely effect of a breakwater?

A) increased erosion of the beach on one side of the breakwater
B) increased longshore current velocities between the breakwater and the beach
C) deflect and dissipate storm wave energy on the seaward side of the breakwater
D) increased sand deposition between the beach and the breakwater

Question 55

are constructed perpendicular to the shoreline and designed to interrupt beach drift and longshore currents that "change" shorelines irrespective of human plans and foreshore engineering works.

A) Seawalls and breakwaters
B) Barrier islands
C) Tidal deltas
D) Groins and jetties

Question 56

A migrates inland as a wave- cut platform is extended.

A) sea arch
B) wave- cut barrier dune
C) wave- cut cliff
D) sea stack

Question 57

What is the landward limit of the shoreface zone?

A) stabilized dunes
B) the low tide line
C) the beach berm
D) the backshore

Question 58

All waves represent .

A) rambunctious gods playing at the edge of the world
B) an interference pattern of crests caused by high tide and troughs caused by low tide
C) energy travel through water, usually caused by wind stress
D) the inertial sloshing of ocean waters caused by Earth's rotation

Question 59

A baymouth bar is .

A) a sand deposit on the seaward side of a tidal inlet to a large estuary
B) a sand deposit extending from a headland partway across the entrance to a bay
C) a sand deposit on the estuary side of gap in a barrier island
D) a sand bar extending across the mouth blocking a former inlet to a bay or estuary

Question 60

are structures built perpendicular to the coast along the entrance to navigable tidal inlets, river mouths, or harbours, to stop them from shifting location or filling with sand from beach drift or longshore currents.

A) Groins
B) Jetties
C) Seawalls
D) Breakwaters

Question 61

The leeward side of a groin is .

A) the site of massive infections by sand- fleas
B) sand starved and particularly prone to erosion
C) a quiet back- water location that fills up with finely laminated muds
D) prone to receive the greatest amount of sand deposition

Question 62

How big are most barrier islands?

A) 1- 5 km wide by 15- 30 km long
B) 1- 5 m wide by 15- 30 m long
C) >100 km wide by > 350 km long
D) 10- 25 km wide by 75- 100 km long

Question 63

Fetch refers to .

A) the distance across open water, over which the wind can blow and generate waves
B) the beachfront area where rapid erosion is taking place
C) the rotational movements of water particles beneath a passing, surface wave
D) the magical creature who secretly moves sediment about when nobody is looking

Question 64

A is a structure built parallel to the shoreline to dissipate much of the energy from incoming waves.

Question 65

are rough rock or reinforced concrete structures built parallel to the coast to protect boats and harbours from the force of large breaking waves.

A) Groins
B) Seawalls
C) Jetties
D) Breakwaters

Question 66

Name two manmade factors that contribute to changes of coastal shoreline environments.

Question 67

refers to the movements of sand and water on a beach face due to a breaking wave.

A) Wash and backslosh
B) Pish and tosh
C) Slash and slosh
D) Backwash and swash

Question 68

How much do moonrise and the time of highest tide change each day?

A) 5 minutes later
B) 50 minutes later
C) 29 minutes earlier
D) 5 hours later

Question 69

A is an isolated remnant of bedrock standing above a wave- cut platform.

A) hoodoo
B) sea spit
C) sea stack
D) sea rampart

Question 70

Briefly give two reasons why, among all geologic environments, the coastal ones are the most fragile in relation to human activity and most prone to sudden change.

Question 71

During the 1960s, a Pacific winter storm hit Queen Charlotte Sound causing waves to break that brushed the underside of the welldeck on one of Shell's exploration wells. Assuming the local water depth was 50 m and the base of the well deck was 20 m above sea level, what was the approximate wavelength for those Pacific storm swells?

Question 72

Which one of the following statements concerning global sea level is correct?

A) It dropped during the past few centuries and that trend will continue because of all the new deep ocean trenches at the subduction zones.
B) It rose over past centuries but will probably drop in the next hundred years because things always average out in the long run.
C) It fluctuates up or down by several centimetres a year but lacks any long term trend.
D) It rose quickly at the end of the last Ice Age but continues to rise slowly due to global warming.

Question 73

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) waves impinging obliquely onto a beach
C) a long fetch parallel to the beach
D) deep- water waves breaking offshore