Ocean Motions
Table of Contents
Wave Action
Tides
Ocean Water Chemistry
Currents and Climate
Ocean Motions - Wave Action
What Is a Wave?
Most waves form when winds blowing across the water’s
surface transmit their energy to the water.
Ocean Motions - Wave Action
Water Motion Activity
Click the Active Art button to open a browser window and
access Active Art about water motion.
Ocean Motions - Wave Action
How Waves Change Near Shore
Near shore, wave height increases and wavelength
decreases.
Ocean Motions - Wave Action
How Waves Change Near Shore
A tsunami is usually caused by an earthquake beneath the
ocean floor.
Ocean Motions - Wave Action
How Waves Affect the Shore
As waves come into shore, water washes up the beach at an
angle, carrying sand grains. The water and sand then run
straight back down the beach.
Ocean Motions - Wave Action
Using Prior Knowledge
Before you read, look at the section headings and visuals to
see what this section is about. Then write what you know
about waves in a graphic organizer like the one below. As
you read, write what you learn.
What You Know
1. There are waves in the ocean.
2. Wind causes waves.
What You Learned
1. Waves move energy to the shore.
2. Earthquakes cause tsunamis.
Ocean Motions - Wave Action
Wave Characteristics
Click the Video button to watch a movie about
wave characteristics.
Ocean Motions
End of Section:
Wave Action
Ocean Motions - Tides
What Causes Tides?
Tides are caused by the interaction of Earth, the moon, and
the sun.
Ocean Motions - Tides
What Causes Tides?
Spring tides and neap tides are
caused by the positions of Earth,
the sun, and the moon.
Ocean Motions - Tides
Plotting Tides
This table lists the highest high
tides and the lowest low tides for
one week at the mouth of the
Savannah River, where it meets
the Atlantic Ocean in Georgia.
Ocean Motions - Tides
Plotting Tides
Graphing:
Use the data in the table to make
a graph. On the horizontal axis,
mark the days. On the vertical
axis, mark tide heights ranging
from 3.0 to –1.0 meters. (Hint:
Mark the negative numbers below
the horizontal axis.)
Check students’ progress as
they make their graphs. The
number –1 should occur at the
base of the y-axis.
Ocean Motions - Tides
Plotting Tides
Graphing:
Plot the tide heights for each
day on the graph. Connect the
high-tide points with one line
and the low-tide points with
another line.
Make certain that students
connect the correct points
with lines.
Ocean Motions - Tides
Plotting Tides
Interpreting Data:
How do the high and low tides
change during the week?
During the first six days, the
high-tide value increases
steadily while the low-tide
value decreases. On day 7,
the trends reverse.
Ocean Motions - Tides
Plotting Tides
Inferring:
What type of tide might be
occurring on day 6? Explain.
Spring tide might be occurring
on day 6, when there is the
greatest difference between
high and low tides.
Ocean Motions - Tides
Previewing Visuals
Before you read, preview Figure 11. Then write two
questions you have about the diagram in a graphic organizer
like the one below. As you read, answer your questions.
Spring and Neap Tides
Q. When do spring tides occur?
A. During the full and new moon phases
Q. What is a neap tide?
A. A smaller tide that happens at the first- and third-quarter moons
Ocean Motions - Tides
More on Tides
Click the PHSchool.com button for an activity about tides.
Ocean Motions
End of Section:
Tides
Ocean Motions - Ocean Water Chemistry
The Salty Ocean
On average, one kilogram of ocean water contains about 25
grams of salts–that is, 35 parts per thousand.
Ocean Motions - Ocean Water Chemistry
Calculating Density
To calculate the density of a substance, divide the mass of
the substance by its volume.
For example, 1 liter (L) of ocean water has a mass of 1.03
kilograms (kg).
Therefore,
Density = 1.03 kg/L
Ocean Motions - Ocean Water Chemistry
Calculating Density
Practice Problem
A 5-liter sample of one type of crude oil has a mass of 4.10
kg. What is its density? If this oil spilled on the ocean’s
surface, would it sink or float? Explain your answer in terms
of density.
The density is 0.82 kg/L (4.10 kg ÷ 5.00 L). The oil would
float on top of the ocean because it is less dense than
ocean water.
Ocean Motions - Ocean Water Chemistry
Changes With Depth
Conditions change as you
descend to the ocean floor.
Ocean Motions - Ocean Water Chemistry
Asking Questions
Before you read, preview the red headings. In a graphic
organizer like the one below, ask a how or what question for
each heading. As you read, write answers to your questions.
Question
Ocean Water Chemistry
Answer
How salty is the ocean?
Ocean water has an
average salt concentration
of 35 parts per thousand.
How does the ocean
change with depth?
As you descend, the
temperature decreases and
the pressure increases.
Ocean Motions - Ocean Water Chemistry
Links on Ocean Water Chemistry
Click the SciLinks button for links on ocean water chemistry.
Ocean Motions
End of Section:
Ocean Water
Chemistry
Ocean Motions - Currents and Climate
Surface Currents
Surface currents, which affect water to a depth of several
hundred meters, are driven mainly by winds.
Ocean Motions - Currents and Climate
Deep Currents
Deep currents are caused by
differences in the density of
ocean water.
Ocean Motions - Currents and Climate
Upwelling
Upwelling brings up tiny ocean organisms, minerals, and
other nutrients from the deeper layers of the water. Without
this motion, the surface waters of the open ocean would be
very scarce in nutrients.
Ocean Motions - Currents and Climate
Relating Cause and Effect
As you read, identify the main factors that cause surface and
deep currents in the oceans. Write the information in a
graphic organizer like the one below.
Cause
Effect
Winds
Surface currents
Differences in oceanwater density
Deep currents
Ocean Motions - Currents and Climate
Links on Ocean Currents
Click the SciLinks button for links on ocean currents.
Ocean Motions
End of Section:
Currents and
Climate
Ocean Motions
Graphic Organizer
How Waves Move
Wind creates a ripple on the ocean surface.
Wave travels as a low swell.
Wave touches the bottom in shallow water.
Wavelength decreases and wave height increases.
Wave breaks on shore.
Ocean Motions
End of Section:
Graphic Organizer