Transcript Volcanoes and Igneous Activity Earth

Chapter 16
The Dynamic
Ocean
Section 16.2
Waves & Tides
16.2 Waves and Tides
Waves
 Wave Characteristics
• Most ocean waves obtain their energy and
motion from the wind.
• The wave height is the vertical distance
between the trough and crest.
• The wavelength is the horizontal distance
between two successive crests or two
successive troughs.
16.2 Waves and Tides
Waves
 Wave Characteristics
• The wave period is the time it takes one full
wave—one wavelength—to pass a fixed
position.
• Fetch is the distance that the wind has traveled
across open water.
• The height, length, and period that are
eventually achieved by a wave depend on three
factors: (1) wind speed, (2) length of time the
wind has blown, and (3) fetch.
Anatomy of a Wave
What is the vertical distance
between a trough and a crest?
A. Wave height
B. Wavelength
C. Wave speed
D. Wave period
Most ocean waves get their
energy from
A. The sun.
B. Plate movement.
C. The moon’s gravitational attraction.
D. The wind.
Which of the following factors
does NOT help determine the
height, length, and period of a
wave?
A. Wind speed
B. Fetch
C. Temperature
D. How long the wind blows
The distance that wind has
traveled across open water is
A. Fetch
B. Wavelength
C. Wave height
D. Wave period
16.2 Waves and Tides
Waves
 Wave Motion
• Circular orbital motion allows energy to move
forward through the water while the individual
water particles that transmit the wave move
around in a circle.
16.2 Waves and Tides
Waves
 Breaking Waves
• Changes occur as a wave moves onto shore.
• As the waves touch bottom, wave speed
decreases. The decrease in wave speed results
in a decrease in wavelength and an increase in
wave height.
Breaking Waves
Energy moves through waves in
a(n)
A. Convection current
B. Circular motion
C. Oscillating motion
D. Straight line
16.2 Waves and Tides
Tides
 Tides are daily changes in the elevation of the
ocean surface.
 Ocean tides result from the gravitational attraction
exerted upon Earth by the moon and, to a lesser
extent, by the sun.
 Tide-Causing Forces
• Gravity is the force that attracts Earth and the moon to
each other.
• Inertia is the tendency of moving objects to continue in a
straight line
• The force that keeps the Earth and moon from
crashing into each other.
Tide Bulges on Earth
Caused by the Moon
The two forces that produce
tides are gravity and
A. Inertia.
B. Friction.
C. Centripetal force.
D. Acceleration.
Ocean tides result largely from
the gravitational attraction of the
A. Sun.
B. Core of Earth.
C. Closest neighboring planets.
D. Moon.
16.2 Waves and Tides
Tides
 Tide Cycle
• Tidal range is the difference in height between
successive high and low tides.
• Spring tides are tides that have the greatest
tidal range due to the alignment of the Earth–
moon–sun system.
• Neap tides are tides that have the lowest tidal
range, occurring near the times of the firstquarter and third-quarter phases of the moon.
Earth–Moon–Sun Positions
and the Tides
16.2 Waves and Tides
Tides
 Tidal Patterns
• Three main tidal patterns exist worldwide:
diurnal tides, semidiurnal tides, and mixed tides.
• A Diurnal tidal pattern has 1 high tide and 1
low tide each day.
• A Semidiurnal tidal pattern has 2 high tides
and 2 low tides each day.
• A Mixed tidal pattern has the same number
of tides as the semidiurnal pattern but tidal
heights vary.
Having one high tide and one
low tide each day is a
A. Diurnal tidal pattern
B. Semidiurnal tidal pattern
C. Mixed tidal pattern
D. Uniurnal tidal pattern
Large tidal ranges caused by
the sun, moon and Earth
alignment are
A. Neap tide
B. Spring tide
C. Diurnal tide
D. Semidiurnal tide