 Please get your science notebook and be in your assigned seat.  Get out your plate boundaries map from yesterday.

1. In pairs, turn your desks so that they are facing each other and almost touching. 2. Take two pieces of paper and place them together vertically into the slight gap between the desks as far down as they can go while still having a grip on the paper. 3. Practice pulling both papers out of the desk at the same time and same rate of movement (this is the spreading mid-ocean ridge)

4. Each student should open a different colored marker. 5. Start with a little bit of paper showing between the desks. 6. As you slowly pull the paper out at the same rate, one student should color both pieces of paper along the ridge with one marker, so that there is a strip of color parallel to the ridge that grows wider as more paper is pulled out. 7. This color represents rocks that are formed with the magnetic minerals facing towards north (normal polarity)

8. The magnetic pole has faded and then shifted south (reversed polarity), and the students should take the second colored marker and make the same type of strip of color in the center of the ridge. 9. Continue to alternate the colors, representing the changing polarity over time.

 Draw arrows showing the direction the seafloor is moving  Mid-ocean ridge  Which strips of color represent N (normal polarity) and which are S (reversed polarity)  Where the oldest rocks are  Where the youngest rocks are

1. Imagine that your hands represent two continents that were once together but must move away from each other as the seafloor grows. You have heard about the continental drift hypothesis and why it was not accepted. Why does the seafloor spreading model provide strong evidence for plate tectonics? 2. The Earth is about 4.6 billion years old. Based on observations of your seafloor spreading model, why do you think that the oldest ocean floor is only about 200 million years old?

3. You will notice that the alternating stripes of normal and reversed polarity are not all of equal width. What does this tell you about the lengths of time of normal and reversed polarity throughout geologic history?

 Use colored pencils and markers to color the different features on the picture. Use each color in a meaningful way!  You may use your own colors and add to the key at the bottom of the page.