OCE1001 Chapter 8
Which is true about ocean waves?
-Classified by their depth of water in which they move. -Described by their period, wavelength, and height. -Ocean waves can be classified by the force that created them.
Which is true about tsunamis?
-The tsunami warning system uses seismic waves and deep-ocean pressure sensors to detect tsunamis. -Tsunamis have very long wavelengths, so they travel at very high speed. -At the coast, a tsunami looks like a suddenly occurring high or low tide. -Tsunamis are undetectable by ships in the open ocean.
Wave period
-the inverse of wave frequency. -the time it takes for one full wavelength to pass a given point.
What is the speed in meters per second of a deep water wave with a wavelength of 1.5 meters?
1.53 MPS
A deep-water wave occurs when the water depth is equal to at least:
1/2 of the wavelength.
How many supertankers or containerships are reported missing each year without a trace?
10
What is the speed in mps of a wavelength of 3.5 meters?
2.34 MPS
What is the speed in mps of a deep-water wave with a wavelength of 5 meters?
2.8 MPS
In the open ocean, 1 wave in ______ will be over twice the height of the wave average.
23
1 wave in ______ will be four times the height of the wave average.
300,000
Which is likely to produce a spilling breaker?
A gently sloping, sandy bottom or rocky bottom
What is a tsunami?
A series of waves that travel away from a fault in all directions at high speed.
A tsunami is considered to be a __________.
A shallow-water wave.
What results when two waves, in phase and with the same wavelength, interact?
A wave with an amplitude that is the sum of the amplitudes of the initial waves.
Rogue waves are created along the "Wild coast" off the southeast coast of _______.
Africa.
Ripple like clouds in the sky are examples of _______ waves.
Atmospheric.
What type of plate boundary are most associated with tsunamis?
Convergent plate boundaries.
As a wave approaches shore, its characteristics change by ______.
Decreasing speed, increases steepness.
Which of the following caused the Indian Ocean tsunami of 2004?
Fault movement.
Which of the following best describes a plunging breaker?
Forms on moderately sloped shorelines to create curling crests.
In general the restoring force for wind-generated waves is:
Gravity.
Why does the wave height of a tsunami increase as the tsunami enters shallow water?
In shallow water, the energy of the tsunami must be contained within a column.
As a wave begins to feel the bottom near a shoreline, its wave height:
Increases and its wavelength decreases.
Sound travels as __________ waves.
Longitudinal.
__________ waves also know as push-pull waves.
Longitudinal.
Which of the following is the least frequent cause of a tsunami in recent centuries?
Meteorite impacts.
What occurs more often, pure destructive, pure constructive, or mixed?
Mixed interference.
Most of the year, and most of the time, the movement of a sediment and water along the California coast is from ___________.
North to South.
Ocean surface waves are:
Orbital waves.
Ocean waves in motion are classified as ___________ waves.
Orbital.
Waves at the ocean surface are __________ waves.
Orbital.
Which ocean is associated with most tsunamis?
Pacific Ocean.
A vast majority of all large tsunamis are generated in the _______ Ocean.
Pacific.
The time between two successive waves is called the:
Period.
Which type of breaker has a curling crest that moves over an air pocket?
Plunging breaker.
Waves that are breaking along the shore and are forming curling crests over air pockets are called:
Plunging breakers.
Submarines sometimes ride out heavy storms in deep-water by submerging. That is a practical application of utilizing the _____________.
Principle of decreasing orbital motion with depth.
Which of the following are names for large waves that can be created by interference?
Rogue waves, Freak waves, Super waves.
Constructive interference results in larger waves whereas destructive interference produces:
Smaller waves.
Which type of breaker is a turbulent mass of air and water that runs down the front slope of the wave as it breaks?
Spilling breaker.
A wave will begin to break when:
Steepness = 1:7
What force is responsible for most ocean waves that eventually break on shore?
Storm-generated winds that blow across the surface.
Which type of breaker forms waves that present the greatest challenge to body surfers?
Surging breaker.
Which type of breaker forms when the wave build up and breaks right a the shoreline?
Surging breaker.
What type of breaker would pose the most danger to people playing or swimming in the surf zone?
Surging breakers.
One that doesn't fit the pattern: -Surf -Swell -Spilling breaker -Surging breaker -Plunging breaker
Swell
What is refraction?
The bending of waves due to a change in wave velocity.
Wave refraction is ____________.
The bending of waves.
What is the relationship between wave base and wavelength?
The depth of the wave base is one-half the wavelength of the waves.
What is the wave height?
The distance between consecutive wave crests or troughs.
What is the wavelength?
The distance between consecutive wave crests or troughs.
Why does wave height increase as waves enter shallow water?
The energy of the wave must be contained within a smaller water column in shallow water.
What is the crest of the wave?
The highest part of the wave.
What is the wave base?
The lower limit of wave-induced motion in water.
What is the trough of a wave?
The lowest part of the wave.
What causes wave refraction?
The part of the wave in shallow water slows down, causing the wave to bend and line up nearly parallel to the shore.
What is an interference pattern?
The pattern produced when two or more waves interact.
What causes the three different types of breakers?
The steepness of the beach slope.
What is the wave period?
The time it takes for one wavelength of a wave to pass a particular point/
What triggers a wave traveling across the ocean to finally release its energy?
The wave begins to interact with the seafloor as it moves into shallower water.
Why do ocean waves bend around headlands?
The waves are moving more slowly just in front of the headland, causing the waves to bend.
Will Sumatra experience another tsunami like 2004?
This is likely, because it is near many ocean trenches.
How are tsunamis generated?
Through displacement of the seafloor under water.
__________ waves also known as side-to-side waves.
Transverse.
Why do ships at sea not notice tsunamis?
Tsunamis in deep water have small wave height and long wave length.
The speed of a shallow-water wave is proportional to:
Water depth.
How does water move as waves pass?
Water moves in the same direction as wave movement.
How does wave amplitude change with depth in water?
Wave amplitude decreases as depth increases.
The depth below the surface where the circular orbits become so small that movement is negligible is called the __________.
Wave base.
The number of wave crests passing a fixed location per unit of time is called the _____.
Wave frequency.
Which of the following statements about wave period is most accurate?
Wave period is the inverse of wave frequency.
The time it takes one full wave to pass a fixed position is called the ______.
Wave period.
How does wave refraction at headlands affect deposition and erosion?
Wave refraction at the headland increases erosion at the headland deposition in adjacent bays.
Waves converge on headlands due to:
Wave refraction.
"Whitecaps" form when ______.
Wave steepness reaches a ratio of 1:7
Wave speed is equal to:
Wavelength divided by period.
The speed of a deep-water wave is proportional to:
Wavelength.
The circular motion of water molecules extends to a depth that is equal to:
Wavelength/2.
What does the term "in phase" refer to?
Waves in phase have identical wavelengths and are aligned peak-to-peak and trough-to-trough.
How are wave period and wavelength related?
Waves with shorter periods have shorter wavelengths.
The largest wind-generated waves tend to be associated with the:
Westerlies.
Conditions for the development of wave energy are most optimal along ______ the shores in _______ Hemisphere.
Western; Southern.
When will perfect destruction interference occur?
When two waves that are 180 degrees out-of phase interference.
When will perfect consecutive interference occur for waves that are in phase and are moving in the same velocity?
When waves with identical wavelengths interfere.
Most ocean waves form as a result of:
Wind's blowing across ocean's surface.
The majority of tsunamis are caused by underwater __________.
fault movement.
The height of a wavelength depends upon:
fetch, wind duration, and wind speed.
Refraction causes headlands to be areas of _______ surfing and sites of ________.
good; erosion
Tidal movement, turbidity currents, wind stress, passing ships at the surface create ________ waves.
internal.
