Modern Evidence and Sea Floor Spreading - Section 5.3

​Page 196 in the book

​Read about Marie Tharp in the My Planet Diary. Answer the question on the next slide.....

Poll

Do you think the ocean floor has valleys and mountains?

• Yes, the bottom of the ocean looks a lot like continental crust

• No, the bottom of the ocean is very flat.

​More about Marie Tharp and her expertise....

​Watch the video carefully and answer the following questions on the slides that follow. Review the video where needed to get the answers correct.

Multiple Choice

What ocean did Marie Tharp and Bruce Heezen collect depth samples from to begin drawing a map of the ocean floor? 

• Atlantic Ocean

• Pacific Ocean

• Indian Ocean

• Arctic Ocean

Multiple Choice

How did they collect the data about how deep the ocean floor was?

• Using echo sounding techniques (high frequency sounds or pings)

• By scuba diving down and recording measurements

• By tieing rocks to long ropes and letting it hit bottom and then measureing

• Using satellite imagery

​p. 196

​p. 197

Multiple Choice

True or False: On the reading on the previous slide it is stated that mid-ocean ridges extend into every ocean on earth. 

• True

• False

• S

​Watch this video on how Sonar works... questions to follow....

Multiple Choice

True or False:  Sonar readings help us see what is underneath the waves. 

• True

• False

Poll

How far below sea level is the peak of this mid-ocean ridge? (measure from the front of the image)

• 1 km

• 1.75 km

• 2 km

• 3 km

Poll

How high from the sea floor does this mid-ocean ridge rise? (again, measure from the front of the diagram) 

• 4 km 

• 3 km 

• 2 km 

• 2.5 km 

Poll

How deep below the peak is the valley marking the center of the ridge?

• about 0.5 km

• about 1 km

• about 2 km

• about 3 km

​page 198

​Sea Floor Spreading

• Harry Hess discovered this process!

• ​He learned that at mid-ocean ridges oceans are creating new ocean crust

• ​Age of ocean floor gets older as you move away from the ridge.

​Watch this video!

​Evidence of Sea floor Spreading

​1. Age of ocean floor

​page 198

​Evidence of Sea floor spreading

​2. Magnetic Stripes on Ocean Floor

​page 198

​Assignment time....

​The next slides contain mulitiple choice or true and false questions about the information presented in this lesson. Use your book pages 196 - 199 to help you answer the questions.

Multiple Choice

Which features form the longest mountain ranges on earth? 

• The Andes

• The Rockies

• mid-ocean ridges

Multiple Choice

Which process adds more ocean crust to the ocean floor? (page 198) 

• suction

• sea-floor speading

• subduction

• magnetic striping

Multiple Choice

Does sea-floor spreading change the size of the ocean?

• Yes

• No

Multiple Choice

True or False: Sonar is a device scientists use to map the ocean floor.

• True

• False

Multiple Choice

True or False: The younger a rock sample is the closer it will be to the mid-ocean ridge.

• True

• False

Multiple Choice

True or False:

The pattern of magnetic stripes in rocks on either side of a mid-ocean ridge is the same.

• True

• False

Open Ended

What are you still confused about from this chapter or this lesson?