DEMO FOR Q2 earth science for grading.pptx

Sea floor spreading demo teaching

1. Seafloor spreading

2. GIVE THREE words THAT would be best to describe the structure and features of the ocean floor and features of the ocean floor.

3. Study the lyrics of “A WHOLE NEW WORLD.” Reflect on the song and prepare to answer the guide's questions.

4. 1. Which lines in the lyrics relate to the lesson? 2. What is the message of the song? 3. Name adjectives describing the features of the earth from the lyrics. 4. What is your understanding of the lesson? 5. Do you think our planet exists as time evolves, leading to a "NEW WORLD"?

5. Think-pair-share Ask your partners to share their ideas about the answers. 1. What is seafloor spreading? 2. What is formed at the mid-ocean ridges? 3. Where is the oceanic crust destroyed? 4. How many inches does the seafloor spread every year?

6. Lesson Vocabulary echo sounder:  device that uses sound waves to calculate distances to underwater objects and the seafloor SONAR : sends a signal that bounces off the underwater object and returns to the receiver. Sonar mapped mid-ocean ridges. seafloor spreading:  hypothesis explaining how the ocean floor forms and how continents can drift Mid-Ocean Ridge – the longest chain of mountains in the world- are divergent plate boundaries. trench:  deep crack in the ocean floor

7. Mapping the mid-ocean ridge:

8. Harry Hess: Studied the Mid-Ocean Ridges Proposed the seafloor spreading theory in 1962. The Sea floor spreading theory states that new ocean crust is being created at mid-ocean ridges and destroyed at deep-sea trenches . .

9. Sea-Floor Spreading???? The process that continually adds new material to the ocean floor.

10. The force responsible for driving or moving the plates is _____________________. Convection Currents occur within the mantle of the earth when hot magma rises and cool magma sinks convection currents

11. Magma, because it is hotter and less dense, is forced up towards the ocean floor cooling off when it touches water. When the magma hardens, a small amount of new ocean floor is added to the Earth ’ s crust. As more magma rises and cools it pushes the new sea floor away from the ridge. This process is called sea floor spreading .

12. Evidence # 1:Molten Material 1. R ocks shaped like pillows. - molten material has erupted again and again from cracks along the mid-ocean ridge and cooled quickly

13. Evidence #2 - Magnetic Stripes Scientists discovered that the rock that makes up the ocean floor lies in a pattern of magnetized “ stripes.” They hold a record of reversals in Earth ’ s magnetic field.

14. Evidence #3 - Drilling Samples The Glomar Challenger did a drilling sample and found rocks that the farther away from the ridge the older the rocks were . The younger ones were in the center of the ridge.

15. Subduction at Deep-Ocean Trenches Deep-ocean trenches The ocean floor plunges into deep underwater canyons, deep-ocean trenches. Subduction - the process by which the ocean floor sinks beneath a deep-ocean trench and back into the mantle.

16. Subduction At deep-ocean trenches, subduction allows part of the ocean floor to sink back into mantle over tens of millions of years. Subduction and Earth ’ s Oceans Earth ’ s ocean floor is renewed about every 200 million years.

17. Subduction in the Pacific & Atlantic Deep ocean trenches are swallowing more oceanic crust than the mid-ocean ridge can produce. Thus, the width of the Pacific will shrink. The Atlantic is expanding. It has short trenches. In some places, the oceanic crust is attached to the continental crust, which moves the continents.

18. Activity Seafloor Spreading

19. Guide Questions: What is the purpose of cutting along the dotted lines of the seafloor-spreading model pattern? How do the colors on the strips represent the age and magnetic polarity of the oceanic crust? Why do you need to tape together the orange ends of the strips? How does threading the strips through the slits simulate the process of seafloor spreading What happens to the strips as you pull them through the slits? How does this relate to the movement of tectonic plates and the formation of subduction zones? What causes the plates to be pulled apart?

20. Short Quiz: 1 whole yellow paper Draw a diagram that illustrates seafloor spreading.) Use arrows to describe the direction of plate motion and label the “youngest” and “oldest” crust

21. Assignment: You receive an e-mail offer to get rich quickly by investing in an undersea gold mine on the Mid-Atlantic Ridge. What scientific issues should you consider before you send a check?