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Oceanography Exam 3
Waves and Water Dynamics, Tides, & The Coast
31
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03/25/2010

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Term
Define wavelength.
Definition
The length from crest to crest.
Term
Define wave period.
Definition
The amount of time that passes between each successive wave break.
Term
Define wave height.
Definition
The height of a wave from crest - trough.
Term
Define wave base.
Definition
The depth in the ocean at which the wave energy dies out.
Term
How does wavelength relate to the celerity (speed) of the wave?
Definition
The bigger the wavelength, the faster the speed.
Term
Describe the movement of water molecule as a wave passes by in deep water.
Definition
Circular.
Term
How does this movement differ when a wave is in shallow water?
Definition
It slows down.
Term
How deep can this energy be felt?
Definition
As deep as the wave base.
Term
How are "deep-water" and "shallow-water" waves defined?
Definition
"Deep-water" waves = the depth of the ocean is greater than 1/2 of the wavelength.
"Shallow-water" waves = the depth of the ocean is less than 1/2 of the wavelength.
Term
Explain how wind speed, wind duration, and fetch determine the height of a wave.
Definition
The faster the wind, the longer the wind lasts, and the bigger the fetch, the bigger the wave.
Term
What is a "fully-developed sea"?
Definition
When it has reached its maximum wave height.
Term
Are waves affected by the Coriolis force? Why or why not?
Definition
No. The Coriolis force only affects moving mass. The ENERGY is what is moving, which is not a mass.
Term
Define constructive wave interference.
Definition
When two wave crests meet and combine their heights.
Term
Define destructive wave interference.
Definition
When two waves meet crest to trough. This results in no waves.
Term
How does a rogue wave develop?
Definition
In a low pressure region where there is wave interference.
Term
What happens to wavelength, height, speed and period when a wave approaches a shoreline? Why does this happen.
Definition
They all decrease, except for the period. This happens because of wave refraction.
Term
If there were no land masses on Earth, how many high and low tides would there be at any given time?
Definition
Two of each. (12 hours apart)
Term
How does gravitational attraction between two objects vary with changes in mass and distance?
Definition
The greater the mass, the stronger the attraction, but the further the distance, the weaker the attraction.
Term
Are tides deep-water or shallow-water waves? Explain.
Definition
Shallow-water, because the depth is less than 1/2 of the wavelength. (The wavelength = 12,000 mi. , and the average depth of the ocean is only 4 mi.)
Term
Define tidal range.
Definition
The difference between the high tide and the low tide.
Term
Describe differences between the daily tidal patterns. (Diurnal, Semidiurnal, and mixed)
Definition
Diurnal = one high tide and one low tide per day.
Semidiurnal = 2 high tides and 2 low tides per day with the same range.
Mixed = 2 high tides and 2 low tides per day with different ranges. (*Most common)
Term
How does tidal range vary with spring and neap tides?
Definition
Spring = highest highs, lowest lows, so Greatest tidal range.
Neap = lowest highs, highest lows, so Smallest tidal range.
Term
How are Moon phases related to monthly tidal patterns?
Definition
It involves the relative positions of the moon, Earth, AND sun. If they all line up, the sun's and the moon's gravitational forces combine (high tides). If they do not line up, their gravitational forces work against each other (low tides).
Term
What is longshore transport?
Definition
The movement of water (and sediment) along the coastline.
Term
Explain how and why a summer beach profile is different from a winter beach profile.
Definition
A summer beach is wider than in the winter because the sand is carried into the water during winter storms, and washes back onto the beach in the summer.
Term
What are the common features of an erosional shoreline?
Definition
(Rocky.) Sea cliffs, sea caves, sea arches, sea stacks, and uplifted marine terraces. (Because the waves carve away at sand)
Term
What are the common features of a depositional shoreline?
Definition
(Sandy.) Beach, spits, bay barrier, barrier islands.
Term
What evidence is there that barrier islands are being moved by wave activity?
Definition
Houses at the edge about to tip and fall into oceans!
Term
How can a seawall actually accelerate shoreline erosion?
Definition
The waves bounce off the wall with the same energy, eroding the beach.
Term
What does beach nourishment/replenishment mean? How does it differ from other shoreline protection methods?
Definition
Pump sand from the ocean floor onto the beach. It is more "natural" - no hardened constructed structures.
Term
What is the main long-term driving force that causes shoreline erosion?
Definition
Global warming, which causes changing sea level (rising), causing extra erosion.