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Oceanography Chapter 8
Oceanography questions
59
Environmental Studies
Undergraduate 4
02/27/2016

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Term
Why are these types of waves called internal waves?
Definition
Because they are internal to the ocean
Term
Why are internal waves usually associated with a pycnocline?
Definition
Because a pycnocline is a boundary between two different water masses with different densities.
Term
Besides where each type of wave is located, what is one of the most obvious physical differences between internal waves and surface waves?
Definition
Internal waves have a much longer wavelength as compared to the shorter wavelength surface waves.
Term
Ocean waves in motion are classified as ______waves.
Definition
orbital
Term
Of the following events, which is/are capable of generating waves?
Definition
Uplift or downdropping of the ocean floor
A storm moving over the ocean surface
A rock falling into a still pond
An underwater landslide
Human activities, such as a ship traveling across the ocean
Term
Of the following statements about ocean waves, which is/are true?
Definition
Ocean waves can be described by their period, wavelength, and height.

Ocean waves can be classified by the way in which they form.

Ocean waves can be classified by the depth of water in which they move.
Term
What is the crest of a wave?
Definition
the highest part of the wave
Term
What is the trough of a wave?
Definition
the lowest part of the wave
Term
What is the wave height?
Definition
the distance between the highest and lowest part of the wave
Term
What is the wavelength?
Definition
the distance between consecutive crests or troughs
Term
What is the wave period?
Definition
the time it takes for one wavelength of a wave to pass a particular point
Term
How are wave period and wavelength related?
Definition
waves with shorter periods have shorter wavelengths
Term
Which of the following statements about wave period is most accurate?
Definition
Wave period is the inverse of wave frequency.
Term
Submarines sometimes ride out heavy storms in deep water by submerging. That is a practical application of utilizing the ____________________.
Definition
principle of decreasing orbital motion with depth
Term
The celerity (speed) of a deep-water wave with a wavelength of 9 meters, relative to that of a deep-water wave with a wavelength of 1 meter, will be ______________.
Definition
faster
Term
You live on an island in the Pacific. An earthquake of magnitude 8.5 off the coast of Japan, 8000 km away, generates a tsunami with a wavelength of 200 km. The average water depth between your island and Japan is 4900 m. If a tsunami warning is issued for your island, how many hours will you have before the waves arrive?
Definition
10.14 hours
Term
What is an interference pattern?
Definition
The wave pattern produced when two or more waves interact.
Term
What results when two waves, in phase and with the same wavelength, interact?
Definition
A wave with an amplitude that is the SUM of the amplitudes of the initial two waves
Term
What does the term "in phase" refer to?
Definition
Waves in phase have identical wavelengths and are aligned peak-to-peak and trough-to-trough
Term
When will perfect constructive interference occur for waves that are in phase and moving at the same velocity?
Definition
When waves with identical wavelengths interfere
Term
When will perfect destructive interference occur?
Definition
When two waves that are 180 degrees out-of-phase interfere.
Term
What occurs more often, pure destructive, pure constructive, or mixed interference?
Definition
mixed interference
Term
Which of the following are names for large ocean waves that can be created by constructive interference?
Definition
Rogue Waves
Superwaves
Freak waves
Term
"Whitecaps" form when _____________________.
Definition
wave steepness reaches a ratio of 1:7
Term
Destructive wave interference results in ___________.
Definition
reduced wave height
Term
Of the following statements about ocean waves, which one(s) describe wave steepness?
Definition
Wave steepness is defined as wave height divided by wavelength.

If wave steepness ever exceeds a 1:7 ratio, then the wave breaks.
Term
Of the following statements about ocean waves, which one(s) describe wave period?
Definition
the inverse of wave frequency

the time it takes for one full wavelength to pass a given point
Term
Of the following waves, which one has the deepest wave base? Select only one answer.

A wave with a 1-meter wave height and a wavelength of 10 meters
A wave with a 2-meter wave height and a wavelength of 1000 meters
A wave with a 3-meter wave height and a wavelength of 100 meters
A wave with a 5-meter wave height and a wavelength of 100 meters
A wave with a 7-meter wave height and a wavelength of 100 meters
Definition
a wave with a 2-meter wave height and a wavelength of 1000 meters
Term
Based on the equations for determining the speed of shallow-water waves, which one of the following variables is necessary to determine the speed of shallow-water waves?
Definition
water depth
Term
Of the following physical changes that occur to waves as they move into shallow water, which is/are true?
Definition
Wavelength decreases.

Wave height increases.

Wave steepness increases.

The waves touch bottom.
Term
How does water move as waves pass?
Definition
Water moves in a CIRCLE in the SAME direction as wave movement.
Term
How does wave amplitude change with depth in water?
Definition
Wave amplitude decreases as depth increases.
Term
What is the wave base?
Definition
the lower limit of wave-induced motion in the water
Term
What is the relationship between wave base and wavelength?
Definition
The depth of the wave base is one-half the wavelength of the waves
Term
Why does wave height increase as waves enter shallow water?
Definition
The ENERGY of the wave must be contained within a SMALLER water column in shallow water.
Term
Why do ocean waves bend around headlands?
Definition
The waves are moving more SLOWLY just in front of the headland, causing the waves to bend.
Term
What is refraction?
Definition
the bending of waves due to a change in wave velocity
Term
How does wave refraction at headlands affect deposition and erosion?
Definition
Wave refraction at the headland INCREASES EROSION at the headland and causes deposition in adjacent bays.
Term
As a wave approaches shore, its characteristics change by _____________________.
Definition
decreasing speed, increasing steepness
Term
Waves usually arrive nearly parallel to the shore because ____________________________.
Definition
waves are refracted toward shallow water
Term
How are tsunamis generated?
Definition
through displacement of the seafloor under water
Term
What is a tsunami?
Definition
a series of water waves that travel away from a fault in all directions at high speed
Term
Why do ships at sea tend not to notice tsunamis?
Definition
Tsunamis in deep water have SMALL wave height and LONG wavelength.
Term
Why does the wave height of a tsunami increase as the tsunami enters shallow water?
Definition
In shallow water, the ENERGY of the tsunami must be contained within a SMALLER water column.
Term
What type of plate boundary are most tsunamis associated with?
Definition
convergent plate boundaries
Term
Which ocean is associated with most tsunamis?
Definition
Pacific Ocean
Term
Will Sumatra experience another tsunami like the destructive one of December 2004?
Definition
This is likely, because Sumatra is near many ocean trenches.
Term
A tsunami watch is issued by the Pacific Tsunami Warning Center when _______________________
Definition
an earthquake with a magnitude greater than Mw = 6.5 occurs beneath the ocean
Term
Of the following offshore ocean conditions, which one(s) would likely produce spilling breakers?
Definition
a gently sloping rocky bottom

a gently sloping sandy bottom
Term
Of the following situations involving orthogonals, which one involves the highest energy? Select only one answer.

Orthogonals that get farther apart as they approach the shore
Orthogonals that become more closely spaced as they approach the shore
Orthogonals that do not change much as they approach the shore
Orthogonals that disappear as they approach the shore
Orthogonals that become oriented parallel to shore as they approach the shore
Definition
orthogonals that become more closely spaced as they approach the shore
Term
By how much would solar have to grow to match the current level of hydroelectric power?
Definition
about 60 times
Term
Which source represents 32% of renewables?
Definition
none of them
Term
Which energy source’s annual growth rate is about four times greater than that of tidal power?
Definition
solar
Term
Assuming that renewable energy sources will contribute more and more to power generation in the future, do you expect the growth rates for these renewable energy sources to increase or decrease over the next 30-year period (2000 to 2030)?
Definition
These growth rates are relative to small absolute numbers. They will most likely decrease as the total contribution by renewables increases.
Term
Which projection has nonrenewables comprising roughly 50% of our energy production in 2050?
Definition
projection 2
Term
Assume depletion of nonrenewables requires renewables (excluding combustibles and waste) to account for more than 30% by 2040. What growth rates of renewables must be achieved and by when?
Definition
at least 15% annual growth rate
Term
A disadvantage shared by wave, solar and wind energy is that ___________________________.
Definition
it is not available on demand, and there currently is no viable way to store the energy
Term
Of the following statements about tsunami, which is/are true?
Definition
At the coast, a tsunami looks like a suddenly occurring high or low tide, which is why they are misnamed "tidal waves."

Tsunami are undetectable by ships in the open ocean.

Tsunami have a very long wavelength, so they travel at very high speeds (equivalent to the speed of a jet airplane).

The tsunami warning system uses seismic waves and deep-ocean pressure sensors to detect tsunami.
Term
Which of the following best describes how scientists help the public prepare for an earthquake event?
Definition
scientists cannot predict when one will occur, but they can identify tectonically active areas that are likely to produce earthquake activity and let the public know if they're in such an area
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