The Movement of Ocean Water

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The Movement of Ocean Water
Chapter 14
Preview
Section 1 Currents Section 2 Currents and
Climate Section 3 Waves Section 4 Tides
Concept Mapping
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Section 1 Currents
Chapter 14
Bellringer
Your teacher will read excerpts from Thor
Heyerdahls Kon-Tiki (1950) or The Ra Expeditions
(1971). Look at the large map of the world that
shows the different ocean currents and the
origination and destination points for
Heyerdahls voyages. Which currents would he have
used to reach his destination? How might you
prove your hypothesis? What kind of data would
you need?
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Section 1 Currents
Chapter 14
Objectives

• Describe surface currents.
• List the three factors that control surface
  currents.
• Describe deep currents.
• Identify the three factors that form deep
  currents.

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Section 1 Currents
Chapter 14
One Way to Explore Currents

• Ocean water contains streamlike movements of
  water called ocean currents.
• Norwegian explorer Thor Heyerdahl proved his
  theory that ocean currents influenced human
  migration by using a raft that was powered only
  by wind and ocean currents.

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Section 1 Currents
Chapter 14
Surface Currents

• Horizontal, streamlike movements of water that
  occur at or near the surface of the ocean are
  called ocean currents.
• Surface currents are controlled by three
  factors global winds, the Coriolis effect, and
  continental deflections.

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Section 1 Currents
Chapter 14
Surface Currents, continued

• Global Winds Winds that blow across the Earths
  surface create surface currents in the ocean.
  Different winds cause currents to flow in
  different directions.
• The Coriolis Effect is the apparent curving of
  moving objects from a straight path due to the
  Earths rotation.

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Section 1 Currents
Chapter 14
The Coriolis Effect
Click below to watch the Visual Concept.
Visual Concept
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Section 1 Currents
Chapter 14
Surface Currents, continued

• Continental Defections When surface currents
  meet continents, the currents deflect, or change
  direction.

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Section 1 Currents
Chapter 14
Surface Currents, continued

• Taking Temperature Currents are also affected
  by the temperature of the water in which they
  form.
• The next slide shows Earths surface currents.
  Warm-water currents are shown as red arrows, and
  cold-water currents are shown as blue arrows.

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Section 1 Currents
Chapter 14
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Section 1 Currents
Chapter 14
Deep Currents

• Streamlike movements of ocean water located far
  below the surface are called deep currents. Deep
  currents are not controlled by wind.
• Deep currents form in parts of the ocean where
  water density increases. The density of the ocean
  is affected by temperature and salinity.

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Section 1 Currents
Chapter 14
Deep Currents, continued

• Formation and Movement of Deep Currents
  Differences in water density cause variations in
  the movement of deep currents.

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Section 1 Currents
Chapter 14
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Section 2 Currents and Climate
Chapter 14
Bellringer
Given the average yearly temperatures for the
Scilly Isles in England and Newfoundland in
Canada, can you explain why the two locations
have very different year-round temperatures? Note
their locations on the globe, and use what you
know about the movement of ocean currents to
support your answer.
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Section 2 Currents and Climate
Chapter 14
Objectives

• Explain how currents affect climate.
• Describe the effects of El Niño.
• Explain how scientists study and predict the
  pattern of El Niño.

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Section 2 Currents and Climate
Chapter 14
Surface Currents and Climate

• Warm-Water Currents and Climate Warm-water
  currents create warmer climates in coastal areas
  that would otherwise be much cooler.

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Section 2 Currents and Climate
Chapter 14
Surface Currents and Climate, continued

• Cold-Water Currents and Climate Cold-water
  currents keep climates along a coast cooler than
  the inland climate year-round.

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Section 2 Currents and Climate
Chapter 14
Surface Currents and Climate, continued

• Upwelling is the movement of deep, cold, and
  nutrient-rich water to the surface of the ocean.
• The nutrients that are brought to the surface
  support the growth of plankton. Plankton support
  larger organisms, such as fish and seabirds.
• Upwelling is shown on the next slide.

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Section 2 Currents and Climate
Chapter 14
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Section 2 Currents and Climate
Chapter 14
Surface Currents and Climate, continued

• El Niño is a change in the water temperature in
  the Pacific Ocean that produces a warm current.
• Effects of El Niño El Niño alters weather
  patterns enough to cause disasters, including
  flash floods, mudslides, and droughts. El Niño
  also prevents upwelling off the coast of South
  America.

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Section 2 Currents and Climate
Chapter 14
Surface Currents and Climate, continued

• Studying and Predicting El Niño Learning as
  much as possible about El Niño is important
  because of its effects on organisms and land.
• To study El Niño, scientist use a network of
  buoys located along the equator. The buoys
  collect data about surface temperature, air
  temperature, currents, and wind.

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Section 3 Waves
Chapter 14
Bellringer
Imagine you are floating in the ocean 1 km from
shore, which is north of you. There is a surface
current flowing east. Are you more likely to
travel north with the waves toward the shore or
east with the surface current?
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Section 3 Waves
Chapter 14
Objectives

• Identify the parts of a wave.
• Explain how the parts of a wave relate to wave
  movement.
• Describe how ocean waves form and move.
• Classify types of waves.

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Section 3 Waves
Chapter 14
Anatomy of a Wave

• Waves are made up of crests and troughs

• A crest is the highest point of a wave.
• A trough is the lowest point of a wave.

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Section 3 Waves
Chapter 14
Wave Formation and Movement

• Most waves form as wind blows across the waters
  surface and transfers energy to the water.
• As the energy moves through the water, so do the
  waves. But the water itself stays behind, rising
  and falling in circular movements.

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Section 3 Waves
Chapter 14
Formation and Movement of Ocean Waves
Click below to watch the Visual Concept.
Visual Concept
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Section 3 Waves
Chapter 14
Specifics of Wave Movement

• Waves not only come in different sizes but also
  travel at different speeds. Wave speed is
  calculated by using the following equation

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Section 3 Waves
Chapter 14
Specifics of Wave Movement, continued

• Wave period is the time between the passage of
  two wave crests (or troughs) at a fixed point.
• The next slide shows how wave period is
  determined.

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Section 3 Waves
Chapter 14
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Section 3 Waves
Chapter 14
Types of Waves

• Deep-Water Waves and Shallow-Water Waves
  Deep-water waves are waves that move in water
  deeper than one-half their wavelength.
• When deep-water waves begin to interact with the
  ocean floor, the waves are called shallow-water
  waves. This process is illustrated on the next
  slide.

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Section 3 Waves
Chapter 14
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Section 3 Waves
Chapter 14
Types of Waves, continued

• Shore Currents When waves crash on the beach
  head-on, the water they moved through flows back
  to the ocean underneath new incoming waves.

• This movement of water forms a subsurface
  current that pulls objects out to sea and is
  called an undertow.

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Section 3 Waves
Chapter 14
Types of Waves, continued

• Longshore Currents are water currents that
  travel near and parallel to the shore line.
• Longshore currents form when waves hit the shore
  at an angle.
• Longshore currents transport most of the
  sediment in beach environments

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Section 3 Waves
Chapter 14
Types of Waves, continued

• Open-Ocean Waves Sometimes waves called
  whitecaps and swells form in the open ocean.
• White, foaming waves with very steep crests that
  break in the open ocean before the waves get
  close to the shore are called whitecaps.
• Rolling waves that move steadily across the
  ocean are called swells.

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Section 3 Waves
Chapter 14
Types of Waves, continued

• Tsunamis are waves that form when a large volume
  of ocean water is suddenly moved up or down. This
  movement can be caused by underwater earthquakes,
  as shown below.

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Section 3 Waves
Chapter 14
Types of Waves, continued

• Storm Surges are local rises in sea level near
  the shore that are caused by strong winds from a
  storm.
• Winds form a storm surge by blowing water into a
  big pile under the storm. As the storm moves onto
  shore, so does the giant mass of water beneath it.

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Section 4 Tides
Chapter 14
Bellringer
If the moon had the mass of a golf ball, the sun
would have the mass of about 110 school buses!
This analogy shows the difference in mass of the
moon and the sun. Although the moon is much
smaller than the sun is, the moon exerts more
influence on Earths tides than the sun does. Why
do you think this happens?
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Section 4 Tides
Chapter 14
Objectives

• Explain tides and their relationship with the
  Earth, sun, and moon.
• Describe four different types of tides.
• Analyze the relationship between tides and
  coastal land.

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Section 4 Tides
Chapter 14
The Lure of the Moon

• The daily changes in the level of ocean water
  are called tides. Tides are influenced by the sun
  and the moon and occur in a variety of cycles.
• High Tide and Low Tide How often tides occur
  and the difference in tidal levels depend on the
  position of the moon as it revolves around the
  Earth.

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Section 4 Tides
Chapter 14
The Lure of the Moon, continued

• Battle of the Bulge When part of the ocean is
  directly facing the moon, the water there and the
  water on the opposite side of Earth bulges toward
  the moon. The bulges are called high tides.
• Water is drawn away from the areas between the
  high tides, which causes low tides to form.

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Section 4 Tides
Chapter 14
The Lure of the Moon, continued

• The figure below shows how the position of the
  moon affects where high and low tides form.

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Section 4 Tides
Chapter 14
The Lure of the Moon, continued

• Timing the Tides Tides occur at different times
  each day because the Earth rotates more quickly
  than the moon revolves around the Earth.

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Section 4 Tides
Chapter 14
Tidal Variations

• The sun also affects tides. The combined forces
  of the sun and the moon on Earth result in tidal
  ranges that vary based on the positions of the
  three bodies.
• A tidal range is the difference between levels
  of ocean water at high tide and low tide.

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Section 4 Tides
Chapter 14
Tidal Variations, continued

• Spring Tides are tides with the larges daily
  tidal range and occur during new and full moons.
  During these times, the sun, Earth, and moon are
  aligned.
• Neap Tides are tides with the smallest daily
  tidal range and occur during the first and third
  quarters of the moon. During these times, the
  sun, Earth and moon form a 90º angle.

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Section 4 Tides
Chapter 14
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Section 4 Tides
Chapter 14
Tides and Topography

• In some coastal areas that have narrow inlets,
  movements of water called tidal bores occur.
• A tidal bore is a body of water that rushes up
  through a narrow bay, estuary, or river channel
  during the rise of high tide and causes a very
  sudden tidal rise.

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The Movement of Ocean Water
Chapter 14
Concept Mapping
Use the terms below to complete the concept map
on the next slide.
waves wavelength crest wave height wave speed

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The Movement of Ocean Water
Chapter 14
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The Movement of Ocean Water
Chapter 14