Cowabunga!

• A wave is a rhythmic movement that carries energy through space or matter

Ocean Movements

Surface Waves cont

• Surface waves have a rolling pattern of particle motion.

• A crest is the highest point of a wave.

Ocean Movements

• A trough is the lowest point of a wave.

The crest-to-crest distance is the wavelength.

Wave CharacteristicsOcean Movements

Wave Height Ocean Movements

– Wave heights depend upon three factors:

1. wind speed

2. wind duration – how long it has blown

3. Fetch – how far that the wind blows across the ocean.

Breaking Waves Ocean Movements

– Ocean waves begin to lose energy and slow down near the shore because of friction with the ocean bottom.

– Breakers are waves where the crests collapse forward when the wave becomes higher, steeper, and unstable as it nears shore.

Breaking Waves

Ocean Movements

Tides• Tides are the periodic rise and fall of sea level.

Ocean Movements

• highest level water rises = high tide

• lowest level water goes down to = low tide.

• daily cycle of high and low tides takes 24 hours and 50 minutes.

Ocean MovementsBay of Fundy

High Tide vs. Low Tide

TidesOcean Movements

Differences in topography and latitude cause three different daily tide cycles.

• The basic causes of tides are

1. the gravitational attraction among Earth, the Moon and the Sun

Ocean Movements

Causes of Tides

Ocean Movements

Ocean Currents

• Density (deep water) current - moves slowly in the deep ocean caused by differences in the temperature and salinity

• Surface currents - wind-driven currents in upper ocean and can move as fast as 100 km per day.

Gyres - continents deflect ocean currents to the north and south causing closed circular current systems

– 5 major gyres: North Pacific, North Atlantic, South Pacific, South Atlantic, Indian Ocean.

• Upwelling - the upward motion of ocean water rich in nutrients which support marine life

UpwellingOcean Movements

Section Assessment1. Match the following terms with their definitions.

___ crest

___ trough

___ tide

___ upwelling

___ breakers

Ocean Movements

A. the upward motion of ocean water, caused by an offshore wind

B. the lowest point of a wave

C. the periodic rise and fall of sea level.

D. the highest point of a wave

E. waves that become higher, steeper, and unstable which causes their crest to collapse

D

B

C

A

E

Section AssessmentOcean Movements

3. Identify whether the following statements are true or false.______Gyres rotate in a counterclockwise

direction in the northern hemisphere.

______ The water in a wave moves steadily forward.

______Wave speed increases with wavelength.

______Spring and neap tides alternate every four weeks.

false

false

true

false

1. Approximately how much of Earth’s surface is covered by oceans?

a. 51 percent c. 71 percent

b. 61 percent d. 81 percent

Multiple ChoiceChapter Assessment

Because most landmasses are located in the northern hemisphere, oceans cover only 61 percent of the surface there. However, 81 percent of the southern hemisphere is covered by water.

2. Of the areas listed below, which generally has the lowest ocean salinity?

a. subtropical regions c. temperate regions

b. tropical regions d. polar regions

In the polar regions, seawater is diluted by melting sea ice. On a localized level, the lowest salinities often occur where large rivers empty into the oceans.

Multiple ChoiceChapter Assessment

Multiple Choice3. Which term below best describes the tide when

the Sun, the Moon, and Earth form a right angle?

a. spring tide c. high tide

b. neap tide d. low tide

Chapter Assessment

During a neap tide, high tides are lower than normal and low tides are higher than normal. During a spring tide the solar and lunar tides are aligned, causing high tides to be higher than normal and low tides to be lower than normal. Spring and neap tides alternate every two weeks.

Multiple Choice4. What is the average ocean surface

temperature?

a. 8ºC c. 15ºC

b. 12ºC d. 18ºC

Chapter Assessment

Surface temperature of Earth’s oceans varies between –2ºC in the polar regions to 30ºC in equatorial regions.

Multiple Choice5. Which of the following is the most prevalent ion

in seawater?

a. chloride c. sodium

b. sulfate d. magnesium

Chapter Assessment

Chloride has a concentration of 19.35 ppt in seawater. It is followed by sodium (10.76 ppt), sulfate (2.71 ppt), and magnesium (1.29 ppt).