What is the world ocean and how is it explored?

By: Mr. D’Angelone

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Learning Objectives

• Students will describe the world ocean.

• Students will explain what is meant by oceanography.

• Students will describe three ways scientists explore the oceans.

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Key Terms

• world ocean

• oceanography

• sonar

• submersible

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The Water Planet

• About 75 percent of Earth's surface is covered with water.

• Most of this is salt water.

• This large body of salt water is known as the world ocean.

• Earth is the only planet in the solar system that has a covering of liquid water.

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Because of its great amounts of liquid water,

Earth is often known as the blue planet.

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Divisions of the World Ocean • The world ocean is divided into three major

bodies of salt water, also called oceans. • These are the Atlantic Ocean, the Pacific Ocean,

and the Indian Ocean. • The word sea is sometimes used as another

name for ocean. • It also refers to a smaller body of water

connected to or near an ocean.• A gulf is a large area of ocean, larger than a bay,

reaching into land.

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The World Ocean

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Size and Depth • The Pacific Ocean is the largest of the world's

oceans. • More than half of Earth's ocean water is in the

Pacific Ocean. • The Pacific is also Earth's deepest ocean. • Its average depth is 4.3 km (2.6 mi).• The Atlantic Ocean is the second largest ocean. • Several seas and gulfs are part of the Atlantic

Ocean. • Its average depth is 3.3 km (2.0 mi).

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Size and Depth (2)

• The Indian Ocean is the smallest ocean.

• It is deeper than the Atlantic Ocean, but not as deep as the Pacific.

• The average depth of the Indian Ocean is 3.8 km (2.3 mi).

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Oceanography

• The study of Earth's oceans is called oceanography.

• Scientists who study the oceans and ocean life are called oceanographers.

• An oceanographer might specialize in the study of the oceans' depths, coral reefs, or the geography of the ocean floor.

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Deep-Sea Drilling • Samples of rock from the ocean floor can

be obtained by drilling. • Studying these samples allows scientists

to learn more about the ocean floor. • The Deep Sea Drilling Project (DSDP) was

an important ocean research program that ended in 1983. (Glomar Challenger)

• The DSDP was replaced in 1985 by another program called the Ocean Drilling Program (ODP). (JOIDES Resolution)

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Sonar

• Scientists can map the ocean floor by using sonar.

• The word sonar comes from the letters in sound navigation and ranging.

• Sonar is an echo-sounding system. • Sound waves travel through water at

about 1,500 m/s. • A transmitter bounces a sound wave off

the ocean floor.

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Sonar (2)

• The returning sound wave, or echo, is picked up by a receiver.

• Scientists can measure the time it takes for the sound wave to return.

• This number can be used to calculate the depth of the ocean floor.

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Sonar uses echoes of sound waves.

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Submersibles

• Scientists also study the oceans by traveling in underwater research vessels called submersibles.

• One of the first submersibles to be developed was a bathysphere.

• The bathysphere remained attached to the research ship.

• Therefore, its movements were limited.

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Submersibles (2)

• Another kind of submersible is called a bathyscaph.

• A bathyscaph is not attached to anything.

• It can hold one pilot and two scientists.

• Robot submersibles equipped with under water cameras can reach great depths and stay there for long periods of time.

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A Bathyscaph

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Checking Concepts

1. About how much of Earth's surface is covered with water?

2. What are the three major oceans?

3. Which of Earth's oceans is the deepest?

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Answers

1. 75%

2. Atlantic, Pacific, and Indian

3. The Pacific

The End