3. Section 1: Currents
By the end of this section, you should be able to:
Describe surface currents.
List the three factors that control surface currents.
Describe deep currents.
Identify the three factors that form deep currents.
4. Surface Currents
Ocean water contains stream-like 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.
5. Surface Currents
Horizontal, stream-like movements of water that
occur at or near the surface of the ocean are called
surface currents.
Surface currents are controlled by three factors:
global winds, the Coriolis Effect, and continental
deflections.
8. Surface Currents
Winds that blow across the Earth’s surface create
surface currents in the ocean. Different winds
cause currents to flow in different directions.
10. Surface Currents
Who can draw a straight line?
The Coriolis Effect is the apparent curving of
moving objects from a straight path due to the
Earth’s rotation.
15. Surface Currents
Currents are also affected by the temperature of
the water in which they form.
On maps, warm-water currents are often shown as
red arrows, and cold-water currents are shown as
blue arrows.
16.
17. Deep Currents
Stream-like 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.
21. Warmup
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 yearround temperatures?
Note their locations on the globe, and use what you
know about the movement of ocean currents to support
your answer.
22. Section 2: Currents & Climate
By the end of this section, you should be able to:
Explain how currents affect climate.
Describe the effects of El Niño.
Explain how scientists study and predict the
pattern of El Niño.
23. Graphing Temperatures
Pair up with a partner.
Select 2 pairs of cities on opposites sides of a
continent. They should all be at approximately the
same latitude.
One city from each pair should be on the coast, the
other should be less than 200 miles inland.
Find the average high and low temperatures for each
city.
Find the average ocean temperature for the coastal
cities.
Display the information on a bar graph.
Explain how ocean temperature affects the climate of
coastal cities.
24. Surface Currents & Climate
Warm-water currents create warmer climates in
coastal areas that would otherwise be much
cooler.
25. Surface Currents & Climate
Cold-water currents keep climates along a coast
cooler than the inland climate year-round.
26. Surface Currents & Climate
Upwelling is the movement of deep, cold, and
nutrient-rich water to the surface of the ocean.
27. Surface Currents & Climate
The nutrients that are brought to the surface
support the growth of plankton. Plankton support
larger organisms, such as fish and seabirds.
28. Surface Currents & Climate
El Niño is a change in the water temperature in
the Pacific Ocean that produces a warm current.
El Niño alters weather patterns enough to cause
disasters, including flash floods, mudslides, and
droughts.
29. Surface Currents & Climate
El Niño also prevents upwelling off the coast of
South America.
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.
31. Warmup
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?
32. Section 3: Waves
By the end of this section, you should be able to:
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.
33. 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.
34. Wave Formation & Movement
Most waves form as wind blows across the
water’s 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.
37. Wave Formation & Movement
Wave period is the time between the passage of
two wave crests (or troughs) at a fixed point.
38. Types of 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.
39.
40. Types of Waves
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.
41.
42. Types of Waves
Longshore currents are water currents that travel
near and parallel to the shore line. They form
when waves hit the shore at an angle.
Longshore currents transport most of the
sediment in beach environments
43.
44. Types of 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.
46. Types of Waves
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.
47. Types of Waves
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.
49. Warmup
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 Earth’s tides than the
sun does. Why do you think this happens?
50. Section 4: Tides
By the end of this section, you should be able to:
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.
51. 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.
How often tides occur and the difference in tidal
levels depend on the position of the moon as it
revolves around the Earth.
52. The Lure of the Moon
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.
53. The Lure of the Moon
Tides occur at different times each day because
the Earth rotates more quickly than the moon
revolves around the Earth.
54. 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.
55. Tidal Variations
Spring Tides are tides with the largest 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.
56.
57. 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.
