1. Reading/pre-thinking—read the article on your desk and answer the questions in your packet.

2. Draw and label the ocean floor landforms.

Any questions (how or why) that we can think of to ask now about the ocean floor?

} Scientists have used echo sounding to figure out the topography of the ocean floor◦ Topography is the surface of land. In this case we

are taking about the land beneath the ocean.

} Because it is impossible to see the sea floor, scientists use a technique called Sound Echoing.

} Sound Echoing is how long it takes a sound wave to go from a ship to the sea floor and back to the ship

Videos: }http://www.youtube.com/watch?v=yFu2676bc6g

}http://player.discoveryeducation.com/index.cfm?guidAssetId=4F6C5920-9267-41B4-9DA0-1C532229B567&blnFromSearch=1&productcode=US

Check for understanding: in 1-2 COMPLETE sentences—summarize what sound echoing or sonar echoing is and what is it used for.

} Sound waves travels 1,520 m/s in sea water.

} So, if a pulse of sound waves makes a round trip in 2 seconds, then it has traveled 1,520 meters to the bottom of the ocean & back up to the surface.

} To find the depth of the ocean at any point, scientists measure the time of the round trip in seconds, multiply that by 1,520 m/s and then divide that by 2.

Formula:

Seconds x 1520Depth of Ocean: ______________

2

What is the formula for finding the depth of the ocean?

Practice:Sound ping sent to the ocean floor and comes up in 6 seconds.—Lets do it together.

Questions: 1. Waves (pings) from an

echo sounder aboard a ship make a round trip in 8 seconds. How far beneath the ship is the ocean floor?

2. Another ship records waves (pings) that make a round trip in 20 seconds. How far beneath the ship is the ocean floor?

Answers: 1. _____________

2. _____________

} We are going Magic School Bus style—down to the bottom of the ocean.

} We are going 9,000-10,000 meters into the ocean to see the ocean floor!

} What kind of scary sea animals will we run into?

In pairs calculate the depth of each creepy crawly ocean animal to find out which animals we will be swimming with.

A scientist sends out Sound wave A that takes 9 seconds to echo back. A second sound wave B takes 14 seconds to echo back.

◦ Which sound wave hit a deeper part of the ocean? (circle one) A or B◦ Which is deeper Abyssal plain or ocean trench◦ Which sound wave (A or B) found an Abyssal Plain?

__________________◦ Which sound wave (A or B) found a Ocean Trench?

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