The World Ocean Exam #2

What are beaches made of?

Whatever type of sediments are locally available

Which beach zone would you find turbulent water with crashing waves?

Surf zone

What type of sediment would be most common on beaches near mouths of rivers?

Fine-grained silt and clay

Which of the following is NOT a characteristic of a summer-time beach?

Large boulders exposed, sand store in offshore sandbar

Where is beach sand 'stored' during the winter-time?

Offshore sand-bars

Longshore drift of sediment occurs how?

Swash transports sand up the beach face at angle, and backwash transports sand straight down the beach face

A coastal cell is composed of ____ that transport sand to shore, -____that distribute the sand along the shoreline, and _____ that transport the sand to the deep-sea.

Rivers/ longshore currents/ submarine canyon

At a beach, the annual input of sand is 5,000 m° and the annual output of sand is 4,500 m3. What would you expect will happen to this beach over time and why?

It will accrete because more sand is gained than lost

Why is Assateague Island, VA disapearing?

Jetties and groins built in Ocean City MD are causing sediment starvation

Why are groins only partly successful in preventing coastal erosion?

They increase the net deposition of sand on the side facing the waves (upstream), but cause net erosion on the side opposite (downstream).

In the longshore drift of sand and water, the upward surge onto the beach face is the ____ and the downward flow is called the ____.

swash/backwash

Which one below is a 'service' provided by dune plants?

They help stabilize the dune by slowing erosion.

Which of the following process would likely happen on a stretch of beach located on the downstream side of a groin?

erosion

A coastal cell is composed of what following features?

river, longshore current, and submarine canyon

The proximal cause for longshore drift of sand is what?

waves hitting beach at an angle

You are constructing a sand budget for the area of the coastline for your town's beach. Which process should you consider as contributing to sand inputs?

longshore transport towards your beach

What should you do if you are caught in a rip current?

drift and wait until you're out of the rip current and then swim ashore

Which one example below is an example of sediment movement perpendicular to the shoreline?

Summertime build-up beach face into a ‘swell profile’

The highest point of a coastal dune are what?

Dune field

Which type of hard stabilization is useful for preventing loss of sand from longshore drift?

Groin

What would happen to a river delta if damming reduced the amount of sediment in the river

The delta would erode and subside below sea level

Which of the following mechanisms of sea level change is NOT eustatic?

Glacial isostatic subsidence and rebound

What would happen to longshore transport along the coast if rivers on the coast were dammed, trapping sand behind the dams

the longshore transport would become less

The crest of an ocean wave is analogous to what part of a tide?

High tide

The wave height, H, of an ocean wave is analogous to what part of a tide?

Tidal range

In the Equilibrium Tide Model predicts two tidal bulges. The tidal bulge on the side of the earth facing the moon is caused by what?

gravity

In the Equilibrium Tide Model predicts two tidal bulges. The tidal bulge on the side of the earth opposite the moon is caused by what?

Centrifugal force

The lunar day is 24 hr 50 min, but the solar day is 24hr. Why the difference?

The Moon (and the lunar bulge) moves around the Earth

Suppose you are a Superhero. With what super-human feat could you increase the length of a tidal day?

Speed-up the rotation of the moon around the earth

A semi-diurnal tidal pattern has ____ high tides and _____ low tides per lunar day.

2, 2

During the ____ and _____ moon phases you experience _____ tides.

1st & 3rd / neap

During the _____ moon phase we observe a ____ tidal range.

New & full / maximum

A maximal tidal range is observed when what?

Earth, moon and sun are lined-up

Why are spring tides highest when the Moon is near perigee?

The Moon is closer to the Earth, so gravitational force is greater

Why does doubling the distance between the Earth and moon have a disproportionally large effect on gravitational attraction than doubling the moon's mass?

because distance is raised to the power of 2

The current that is created from an out-going tide is a _____ current.

Ebb

What are the two moon phases associated with a spring tide during a typical lunar month?

new and full moons

During a neap tide, the tidal range is very small, because of the opposing gravitational attractions of the sun and moon. This is similar to what phenomenon you learned about in the waves chapter?

destructive interference

What the two most common periods for the tides?

diurnal and semidiurnal

During what moon phase are you most likely to experience a spring tide?

full moon

Which ONE of the following below describes a typical semidiurnal tide pattern?

two low tides and two high tides per day

The equlibrium model of the tides predicts what type of tide?

semidiurnal

Why does the distance between two astronomical bodies such as the Moon and Sun have a larger impact on Earth's tides than the masses of the two bodies?

Because distance is raised to the power of 2 and mass is to the power of one.

At what position in an amphidromic system is the tidal range equal to zero?

At the node, or amphidromic point

High tide corresponds to what part or characteristic of a wind-generated wave?

crest

Which parameter in Newton’s equation does the elliptical shape of the moon’s orbit have a direct effect upon?

r - the distance between Earth and moon

In the ideal (equilibrium) tidal model, where would the maximum lunar tidal range occur ?

At two points, directly beneath and opposite the Moon.

The sun’s gravitational force (Fg) on earth’s oceans is maximal when the earth and sun are in what orientation?

perihelion

The maximal tidal range is associated with the ________tides and the minimal tidal range with the ___________ tides.

Spring, neap

The Dynamic Model of the tides assumes what?

Real bottom bathymetry

In an amphidromic system the maximum tidal range is found_________ and the minimum tidal range is found_________

Along the outer edges/ at the node

In an amphidromic system the co-tidal lines are bent (refracted) because of what?

The ocean depth varies, so tide speed varies

The outgoing tide is called a _____ tide and the incoming tide is called the _________ tide

Ebb/flood

Maximum tidal current speed is found when?

Half-way between high and low tide

In the diagram above, what letter is the wave height?

A

In the diagram above, what letter is the wavelength?

C

The wave base depth is:

One-half the wavelength

A wave has a period (T) of 10 seconds. It's frequency (f) is _____ per second:

0.1

When a wave enters shallow water, it first begins to slow down when the water depth is:

equal to ½ the wavelength

When waves enter shallow water, their characteristics change how?

They slow down, get closer together, and get taller

Wave dispersion occurs when:

Longer wavelength waves move out ahead of shorter wavelength waves because of their faster speed

When a wave approaches the shoreline at an angle, the part of the wave in shallower water moves slower than the part in deeper water, causing the wave to have a bend in it. This is called:

Refraction

Surfers love to catch ____ breakers, so they will work a beach with a ____ sloped seafloor:

Plunging/moderately

A standing wave or a seiche can form where?:

In an estuary or semi-enclosed bay & in a lake

The speed of a deep-water wave is determined by its ______.

wavelength

A ______ breaker is the wave favored by surfers.

Plunging

The three factors that affect the energy in an ocean wave are:

wind speed, fetch, and duration of wind

The speed of a shallow water wave is determined by what?

Water depth

The depth to which the circular motion of a passing surface ocean wave is felt is called what?

wave base

If you stood at the end of a pier with a stop-watch, and you counted the number of waves that hit the pier piling in one minute, and calculated the #waves per minute, this is called what?

frequency

An ocean wave requires which one of the following to form?

a disturbing force, such as wind, or earthquake

A surface ocean wave is _______.

energy in motion

The area over which the wind blows and creates a wave is called the _____.

fetch

What is the best definition for a deep-water wave?

A wave whose wave base is shallower than the depth to the seafloor

A wave has a wavelength (L) of 100 meters and a period (T) of 50 seconds. Its wave speed is ________ meters per second:

2

If a wave has a wavelength of 140 meters, what is the depth to its wave base?

70

The speed of deep-water waves is determined by what ONE factor?

Wavelength

A fully-developed sea occurs when the ocean waves are in balance with _____________.

wind speed

Wave dispersion is not seen in shallow-water waves because

Their speed is controlled only by water depth and not by wavelength

If the first part of a tsunami wave to strike the shore is the wave’s trough, this would appear to observers on the shoreline as:

A sudden out-going low tide

If you were a submarine commander and wanted to go deep enough that your sub would not feel the effect of 300-foot (91-m) wavelength storm waves, how deep would you have to dive?

At least 150 feet

In order to achieve constructive interference of two waves, what conditions must be met?

The wave crests of both wave sets must be in-phase

When two wave sets combine, and the resulting wave crests and troughs don’t perfectly align, this type of interference is called:

mixed interference

Why does a wave crest refract (bend) when approaching the shoreline?

The end of the wave nearer shore “feels the bottom” first and is slowed before the other end of the wave

What conditions must be met in order for an air mass to create a high-pressure zone at ground level?

The air mass must be more dense than the air around it.

Ground level air movement (wind) always travels from a zone of _____ pressure to a zone of ____ pressure.

High, low

The movement of air from the ground level to the top of the atmosphere, and back again is called what?

A circulation cell

The three atmospheric circulation cells, from the poles to the equator, are the:

Polar, Ferrel, Hadley

Which of the boundary regions is located near the equator, and has warm, moist air that is rising?

Doldrums

Which one of the following is the best descriptor for the horse latitudes boundary region?

Warm, dry air, sinking

Which one of the following wind belts is located just north and south of the equator?

Trade Winds

Which one of the following statements is correct?

Warm, moist air rises and forms a low-pressure zone at ground level

The circulation cell situated between the horse latitudes and the polar front is called the:

Ferrel Cell

As a result of the Coriolis effect in the northern hemisphere, winds are deflected:

to the right of the original direction.

Westerlies is to Ferrel cell as _____ is to Hadley cell.

trade winds

Which northern hemisphere wind belt is located between the doldrums and horse latitudes?

northeast trade winds

The movement of air parallel or nearly parallel to lines of latitude is called:

zonal wind flow

The area of the globe (latitude) that is characterized by falling air masses and little precipitation is:

30 degrees latitude

In the southern hemisphere if the wind is blowing steadily to the east, the resulting Ekman transport in the ocean's Ekman layer is in which direction?

north

The wind belt in Lancaster county is:

westerlies