Chapter 16

The Dynamic Ocean

Section 16.2

Waves & Tides

Waves Wave Characteristics

16.2 Waves and Tides

• 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.

Waves Wave Characteristics

16.2 Waves and Tides

• The wave period is the time it takes one full wave—one wavelength—to pass a fixed position.

• 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.

• Fetch is the distance that the wind has traveled across open water.

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

Waves Wave Motion

16.2 Waves and Tides

• 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.

Waves Breaking Waves

16.2 Waves and Tides

• 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

Tides

Ocean tides result from the gravitational attraction exerted upon Earth by the moon and, to a lesser extent, by the sun.

16.2 Waves and Tides

Tides are daily changes in the elevation of the ocean surface.

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.

Tides Tide Cycle

16.2 Waves and Tides

• Spring tides are tides that have the greatest tidal range due to the alignment of the Earth–moon–sun system.

• Tidal range is the difference in height between successive high and low tides.

• Neap tides are tides that have the lowest tidal range, occurring near the times of the first-quarter and third-quarter phases of the moon.

Earth–Moon–Sun Positionsand the Tides

Tides Tidal Patterns

16.2 Waves and Tides

• 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 areA. Neap tide

B. Spring tide

C. Diurnal tide

D. Semidiurnal tide