Ch 4 Test Flashcards
what Generates forces of ocean waves
Wind, earthquakes (causing tsunamis) and landslides (including ice breaking off of glaciers)
What do waves start as?
capillary waves aka ripples in the water
As more energy is captured by the ocean what waves develop.
larger, or gravity waves
Swells
Waves that have moved
out of their area of
origin. They have long
wavelengths, with
regular pattern of crests
and troughs. They have
large amount of energy
and lose it slowly.
Tsunamis
series of waves,
generated in a body of
water by an impulsive
disturbance that
vertically displaces the
water column.
Landslides
When a large piece of
land of glacier breaks
off and displaces the
water it falls into. When
the displaced water
comes back, the
movement causes a
series of waves.
Wind speed
high wind speed, higher the
waves.
Water depth
waves forms more easily in
shallow water.
Fetch
the duration that the wind blows in
one direction.
Three Factors of Wave Height
Wind speed, fetch and wind duration.
Why would between 40 S and 50 S be considered the most favorable conditions for maximum wave formation?
Large areas of open ocean with little landmass
to interfere with fetch. Also, almost constant
westerly winds in the area add to duration.
What are the two restoring forces of wave dissipation?
- Surface tension restores capillary waves
- Gravity restores the larger gravity waves.
Waves
are energy that moves through the
water.
Do waves transport water?
It does not move water
particles(transport water)
Potential energy
energy stored in the height of the
wave.
Kinetic energy
energy from the motion of the water
particles of the wave
Orbital Waves
particles move in a circular
path.
Crest –
highest point of a wave.
Trough
– lowest point of a wave.
Still Water level –
equilibrium
Wave height(amplitude)
the vertical distance
from crest to trough.
Affected by wind speed, wind duration, and fetch
Wavelength
the horizontal distance between
two consecutive crests.
Wave period –
The time required for the wave
to crest at Point A to reach Point B
Frequency
The number of wave crests
passing point A each second
Wave Cancellation
Crest of one wave meets
the trough of another. Wave energy is cancelled.
Wave Reinforcement
Two crests or two
troughs meet in sinc and add to increase the
water height.
Rogue Waves
Large waves that seem to appear out of nowhere and are unrelated to local sea conditions
When do rouge waves occur
when various storm waves
collide with each other reach near the edges of continental shelves and where there are constant wind, wave and current patterns.
For deep-water waves, the wave must occur in
water that is deeper than ___ the wave’s length.
1/2
Do orbits reach the ocean floor?
The orbits do not reach the ocean floor
For deep-water waves, the longer the wavelength, the _____ the wave travels.
faster
What is the result of the orbits interacting
with the seafloor?
As the wave approaches the shore, its orbit is affected by the bottom. The orbit becomes flattened (elliptical) and the forward speed of the wave is reduced because of friction.
Water depth is less than ___ of the
wavelength, a shallow-water wave begins to
form.
1/20
Surf Zone
- the area of the continental margin
where waves release their energy
As the speed slows, the wavelength ______ and the height _______.
shortens, increases
What changes to wave height and wave speed would you expect as waves enter the shoaling
zone?
a. Both wave height and wave speed increase.
* b. Both wave height and wave speed decrease.
* c. Wave height increases while wave speed decreases.
* d. Wave height decreases while wave speed increases
c. Wave height increases while wave speed decreases.
spilling breakers
results in gently
sloping ocean bottom. Losses
energy more slowly than the
others.
plunging breakers
results
in moderately steep ocean
bottoms
surging breaker
results from
the ocean bottom having an
abrupt slope. Energy is
compressed into a short distance
and waves break quickly.
Sediment
As waves move down the shore,
they move sand and sediment down a beach.
Water
Water is moved along beach as well
Rip Currents
Because of waves, water is transported towards the shore. Water then flows along the shoreline until it reaches an area where it can flow seaward again. These areas are
usually narrow and distances apart. This leads to the formation of rip currents.
Three Indicators of a Rip Current
1) turbid water and floating debris moving seaward.
2) areas of reduced wave height.
3) depressions in beach, perpendicular to shore.
Rip currents are commonly observed on beaches
with a _____ slope.
gentle
tsunami
a wave train, or series of waves, generated in a body of water by an impulsive disturbance that vertically
displaces the water column.
Tsunamis are shallow water waves in all oceans. Why?
Depth of wave base is equal to roughly ½ the wavelength. Since most tsunamis wavelengths are about 125 miles, the ocean depth would have to be greater than 62 miles. There is no part of any ocean basin that is
deeper than 62 miles. Example: Mariana Trench is only 7 miles deep.
What is a tide?
The rise and fall of the
sea, usually twice in
each lunar day at a
particular place due to
the attraction between
Earth and the moon and
Earth and the sun.
Interdial Zone
a marine ecosystem existing due to the rise and fall of the daily tides
Lunar Day
24 hours and 50
minutes
Why do the times for high tides and low tides in an
area vary each day?
The Earth must rotate an extra 50 minutes to
align directly with the Moon again.
Monthly tidal cycle(lunar cycle) is _________
29 ½ days
Diurnal tide
1__high tide; __1__ low tide
each day. Common in shallow inland seas and bays.
Semidiurnal tide
__2___ high tides; __2 low tides each day. Common Atlantic coast of the US, west coast of Africa
Mixed tide
Usually: __2_ high tides; __2__
low tides each day.
Minus tide
A low tide that falls below the mean average.
A rising tide is called a—
flood tide
A falling tide is called an
ebb tide
When does slack water occur?
When tidal currents slow and reverse.
Tidal bores
true tidal waves; Tidal bores usually form along shallow bays and
river mouths because of
the sharp change in
water depth forces the
rising tide at great
speed against the out
flow of river water.
For a tidal bore to form, four main factor must exist:
1 - Exceptionally high spring tidal range.
- # 2 - Shape of channel that grows narrow andshallow, upriver.
- # 3 – abrupt rise of flood tide but a long ebbtide phase.
- # 4 – low-lying river with a consistent seawardflow of water.
