Classroom activity worksheet explaining sea-floor spreading using colored paper and a diagram.

Problem Overview:

The task involves creating a paper model to simulate how the ocean floor is created at mid-ocean ridges and how it spreads into tectonic plates. The activity focuses on understanding sea-floor spreading, which is a key concept in plate tectonics.

Solution and Explanation:

#### Step-by-Step Instructions:

1. Go to the 5th page of this activity:
- This step directs you to the specific page where the instructions or materials for the activity are located. Ensure you are on the correct page before proceeding.

2. Cut out two strips of paper with colored pencils marked on them (orange, yellow, green, and blue):
- Use scissors to cut out two rectangular strips of paper. Each strip should have four colored sections (orange, yellow, green, and blue) marked along its length. These colors represent different layers or features of the ocean floor as it spreads.

3. Cut out one copy of the sea-floor spreading pattern model that you just colored:
- Locate the sea-floor spreading pattern model on the page and carefully cut it out. This model will serve as a guide for assembling your paper strips.

4. On the 6th page of this activity, fold the paper in half lengthwise:
- Take a new sheet of paper and fold it in half lengthwise. This folded paper will act as the base for your model.

5. Go to the 7th page of this activity:
- Move to the next page, which likely contains further instructions or diagrams to help you assemble the model.

6. Cut out a piece of paper about the size of the folded paper (ONLY CUT THE DOTTED LINES). Do not cut the paper on the way up the dotted lines. You have to fold the paper over and start cutting from the other side:
- Cut out a rectangular piece of paper that matches the size of the folded paper. Only cut along the dotted lines provided in the instructions. This ensures that the paper can be folded correctly without being completely separated.

7. Thread the two strips that you taped together through the slit (Slit B):
- Take the two colored strips you prepared earlier and thread them through the designated slit (Slit B) in the folded paper. This simulates the movement of the ocean floor as it spreads.

8. Take the other ends of the strips and tape them to the back of the paper:
- Secure the ends of the strips to the back of the folded paper using tape. This keeps the strips in place and allows you to manipulate them easily.

9. Pull the strips through the slits (all A and C) so that the same colors on both strips line up:
- Pull the strips through the other slits (A and C) and adjust them so that the corresponding colors on both strips align perfectly. This represents the symmetrical spreading of the ocean floor.

10. Look at the diagram below to get an idea on what your model should look like:
- Refer to the provided diagram to ensure that your model accurately represents the sea-floor spreading process. The diagram will show how the strips should be aligned and positioned.

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Key Concepts Explained:

1. Sea-Floor Spreading:
- Sea-floor spreading occurs at mid-ocean ridges, where new oceanic crust is formed as magma rises from the mantle and solidifies. As the crust forms, it moves away from the ridge, causing the ocean floor to spread outward.

2. Symmetry:
- The ocean floor spreads symmetrically on either side of the mid-ocean ridge. This is why the colored strips in the model need to be aligned so that the same colors match up.

3. Tectonic Plates:
- The spreading of the ocean floor leads to the formation of tectonic plates, which move apart over time. This activity helps visualize how these plates are created and how they move.

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Final Answer:

By following the steps outlined above, you will create a paper model that demonstrates the process of sea-floor spreading. The model will show how new oceanic crust forms at mid-ocean ridges and how it spreads outward, leading to the creation and movement of tectonic plates. The final product should resemble the diagram provided in the activity, with aligned colored strips representing the symmetrical spreading of the ocean floor.

Boxed Final Answer:
$$
\boxed{\text{Follow the steps to create a paper model demonstrating sea-floor spreading.}}
$$