Oceans S6E3. Students will recognize the significant role of water in earth processes. a. Explain...

Oceans S6E3. Students will recognize the significant role of water in earth processes.a. Explain that a large portion of the Earth’s surface is water, consisting of oceans, rivers, lakes, underground water, and ice.c. Describe the composition, location, and subsurface topography of the world’s oceans.d. Explain the causes of waves, currents, and tides.

Oceans S6E5. Students will investigate the scientific view of how the earth’s surface is formed.f. Explain the effects of physical processes (plate tectonics, erosion, deposition, volcanic eruption, gravity) on geological features including oceans (composition, currents, and tides).

How are geological features that exist on land similar to those on the ocean floor?

Terms to know:

• Sonar—sound navigation and ranging; system that uses sound waves to measure distances; has enabled scientists to map much of the ocean floor

• Continental shelf—gently sloping shallow area of the ocean floor extending outward from the edge of a continent


Terms to know:

• Continental slope—steep incline extending beyond the continental shelf to the deep ocean floor

• Abyssal plain—smooth, nearly flat region of the ocean floor

• Mid-ocean ridge—underwater mountain range that winds through the oceans


Terms to know:

• Trench—deep, steep-sided canyon in the ocean floor

You should remember mid-ocean ridges and trenches from our study of plate tectonics. How are these two features related?


Terms to know:

• Intertidal zone—the part of the ocean between the highest high-tide line to the lowest low-tide line

• Neritic zone—the part of the ocean extending from the lowest low-tide line out to the edge of the continental shelf

• Open-ocean zone—the deepest, darkest part of the ocean beyond the continental shelf


Questions to consider:

• Why has the deep ocean floor been explored only recently?

• Which statements are true about the ocean floor? Which are false? • It is flat and sandy• It is rocky and uneven• It has the biggest mountains on Earth.• It has deep canyons.


Questions to consider:

• What are the three zones which make up the open-ocean zone?• Surface zone• Transition zone• Deep zone

What’s in the ocean water?• It’s salty

• Table salt, or sodium chloride, NaCl, is the most common salt, but other salts include magnesium chloride, magnesium sulfate, calcium sulfate, calcium carbonate and others

What’s in the ocean water?• Salinity—total amount of dissolved salt

in a sample of water

On average, 1 kg of ocean water contains about 35 grams of salt—we say 35 ppt (parts per thousand)

What’s in the ocean water?• Factors affecting salinity

What’s in the ocean water?• Effects of salinity

• Increases density

What’s in the ocean water?• Effects of salinity

• Lowers the freezing point of water

What’s in the ocean water?

• Temperature variations• Sun warms the ocean water at the

surface• Surface temperatures are warmer near

the equator and lower as we move away from the equator

• Deeper in the ocean, the temperature decreases

• Cold water is denser than warm water


• Gases in the ocean• Gases are dissolved in ocean water• Ocean organisms need oxygen and

carbon dioxide• Surface water has more oxygen

because of photosynthesis, which cannot occur in deeper water

• Cold water dissolves more oxygen• Deeper water contains more carbon

dioxide


• Changes with depth

• Temperature decreases as you go deeper in the ocean; average temperature in the deep zone is 3.5 °C

• Pressure increases with depth

Why does a sailboat move in the ocean?

Why does a sailboat move in the ocean?

Energy from wind transfers

to the boat

In the same way, energy from wind transfers to the ocean’s

surface, creating waves.

Which has more energy—

a strong windor

a gentle breeze?

Size of Waves• Strength of the wind

• Length of time wind blows

• Distance over which it blows

Waves move energy—

not water

Parts of a Wave

•Crest—the highest point of a wave•Trough—the lowest point of a wave

Parts of a Wave

•Wave height—the distance from the crest to the trough

•Wavelength—the distance between crests

Parts of a Wave

•Frequency—the number of waves that pass a point in a certain amount of time

As waves approach shore,

the wave height increases and the wave-length decreases. The energy causes the water to push up on beach, but gravity pulls it back to sea.

Tsunami

Tsunami

• Caused by • Underwater earthquake• Landslide• Underwater volcano

• Most common in the Pacific Ocean

• Longshore drift—the movement of sand along a beach.

Effects of Waves

Effects of Waves

What causes tides?

• Tides—the daily rise and fall of Earth’s waters on its coastlines

• High tide—when the water reaches its highest point

• Low tide—when the water reaches its lowest point

What causes tides?• Tides occur regularly—two high tides and two low tides each day (about every 25 hours)

• Each high tide occurs about every 12 ½ hours; each low tide occurs about ½ way between

• Tides occur in a cycle—high tide then low tide then high tide…

What causes tides?

• Tides are caused by the gravity of the moon pulling on Earth’s waters

What causes tides?• The moon’s gravity causes a tidal bulge of water on the side of Earth closest to the moon; the waters on the other side are “left behind” and create a second bulge

What causes tides?

• The sun is also involved in tides

• Two special tides occur each month because of the sun’s gravity

• Spring tides and neap tides

What causes tides?• Spring tide—the greatest difference between high and low tide

• High tides are their highest; low tides are their lowest

What causes tides?• Spring tides

• The sun’s gravity combines with the moon’s gravity

• Occur at new moon and full moon

• Sun, Earth and moon are in a straight line

What causes tides?• Neap tide—the least difference between high and low tide

• High tides are lower than usual; low tides are higher than

What causes tides?• Neap tides

• The sun’s gravity competes with the moon’s gravity

• Occur at 1st and 3rd quarter moons

• Sun, Earth and moon are at right angles

What causes currents?

• Currents—large streams of moving water that flow through the oceans

• Types of currents• Tidal• Surface• Deep


• Surface currents—affect water to a depth of several hundred meters

• Driven mainly by winds

• Move in a circular pattern


• Why do currents move in a circular pattern?


• Why do currents move in a circular pattern?

• The Coriolis effect—the effect of Earth’s rotation on the direction of winds and currents

• Does the Coriolis effect work the same all over the Earth?


• Does the Coriolis effect work the same all over the Earth?• Currents in the Northern

Hemisphere curve to the right, or clockwise

• Currents in the Southern Hemisphere curve to the left, or counterclockwise


• Surface currents warm or cool the air above them, influencing the climate of the land near the coast

• Currents affect climate by moving cold and warm water around the globe


• The Gulf Stream is the largest and most powerful surface current in the North Atlantic Ocean. It carries more water than the Mississippi!


• Does the Gulf Stream carry warm water or cold water?• (hint: look at where it originates)


• The warm waters of the Gulf Stream bring a mild climate even to areas near the Arctic, such as Norway


• The Gulf Stream is a warm water current, originating in the warm waters of the Gulf of Mexico

• Currents which flow from waters near the equator toward the poles are warm currents

• Currents which carry water from the poles toward the equator are cold currents

Can you tell which currents are cold currents and which

are warm currents?

Notice the Coriolis Effect—which curve right and which curve left?


• El Niño is abnormal climate event that occurs every 2 to 7 years in the Pacific Ocean• Unusual pattern of winds in the

western Pacific pushes a huge amount of water toward the South American coast

• Unusual weather patterns around the world


• Deep currents move water at greater depths, even along the ocean floor• Move much more slowly than

surface currents• Also called thermohaline currents


• Deep currents, or thermohaline currents• Caused by differences in density,

due to temperature and salinity variations

• What factors affect ocean water temperatures?

• What factors affect salinity?


• Factors affecting salinity


• Deep currents move and mix water around the world. They carry cold water from the poles toward the equator.


• Upwelling—the upward movement of cold water from the ocean depths to replace warm surface water moved away by winds• Bring up ocean organisms,

minerals, and other nutrients from the deep

• Without upwelling, surface waters would have little nutrients

Scientists have used accidents to track

currents

• In 1992, a cargo ship lost several containers during a violent storm in the Pacific

Scientists have used accidents to track

currents

• One of the containers broke apart—it was carrying thousands of toy ducks!

What have I learned about the ocean?

• Subsurface topography (features of the ocean floor• Salinity and factors affecting it• Causes of ocean waves and parts of a wave• Causes of tides and how special tides occur• Causes of currents, surface and deep, and how they affect climate

Oceans S6E3. Students will recognize the significant role of water in earth processes. a. Explain...

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