Ocean Motions Study Guide
Surface currents usually flow more quickly than deep currents. (T)
Deep currents are caused by differences in pressure. (F; density)
The most common salt in ocean water is calcium sulfate. (F; sodium chloride)
A rip current is caused by an earthquake on the ocean floor. (F; tsunami)
The farther apart waves are, the greater their wavelength. (T)
The largest and most powerful surface current in the North Atlantic Ocean is the Gulf Stream.
The density of seawater depends on its temperature and salinity.
Oxygen in ocean water comes from the atmosphere and algae.
Gravity is the force that causes tides.
The horizontal distance between crests of waves is the wavelength.
In the Northern Hemisphere, ocean currents curve to the right because of the Coriolis effect.
Both surface currents and waves are caused mainly by winds.
As you go deeper in the ocean, pressure does NOT decrease.
Two gasses found in ocean water that are necessary for living things are oxygen and carbon dioxide.
Low tides occur about every 12 hours and 25 minutes.
A spring tide occurs when the moon, sun, and Earth are in a straight line.
The total number of high tides that occur each day in most places is two.
Tsunamis are most common in the Pacific Ocean.
The strength of a wave depends mainly on its wave height.
When a wave passes by, water particles move in a circular motion.
How do waves change as they near the shore? Explain your answer. As the water becomes more
shallow, the bottoms of the waves drag on the ocean floor and slow down. This makes the wavelength
decreases. The water piles up, causing the wave height to increase.
Why are large numbers of fish often found in zones of upwelling? Upwelling brings up tiny ocean
organisms, minerals, and other materials from deeper layers of the water, increasing the supply of
nutrients.
Using the major ocean currents map on page 457 you will have to identify which on the ocean
currents are cold currents and which are warm currents. Explain the reasoning for your choices. Cold
currents: 1, 2, 6, 8, 9, 10; warm currents: 3, 4, 5, 7. Generally, ocean currents carry warm water from the
tropics toward the poles or carry cold water from the poles toward the equator.
How are ocean currents in the Northern and Southern Hemisphere alike? How are they different?
They are alike in that they move in circular patterns in the major ocean basins. They are different
because they curve to the right in the Northern Hemisphere and to the left in the Southern Hemisphere.
Along the very southern coast of South America, winds blow from west to east. Based on the map on
p.457, predict what the climate is like along the southwest coast of South America. Explain your
answer. The climate along the west coast of South America is cool and dry because a cold current flows
along that coast, causing the air above it to be cool and dry.
How do you describe the relationship between ocean depth and water pressure? Water pressure
increases steadily with increasing depth.
In what ways is the ocean at a depth of 1,000 meters different from the ocean at the surface in the
same location? Compared with the surface of the ocean, the ocean at 1,000 meters deep is dark
because on sunlight penetrates below about 200 meters. The ocean at 1,000 meters deep is an average
of 13.3 degree C colder than the surface, as well as saltier. Because the deeper water is colder and
saltier, it is also denser. The pressure at 1,000 meters deep is about 100 times that at the surface.
Do you think that you would float more easily in the middle of the Pacific Ocean or the Arctic Ocean?
Explain your answer. You would float more easily in the Arctic Ocean because its cold, highly saline
water is denser than the warmer, less saline water of the middle of the Pacific Ocean.