Modeling Sea-Floor Spreading Lab Activity




Problem

How does sea-floor spreading add material to the ocean floor?

Materials
Scissors
Metric ruler
2 sheets of unlined paper
Colored marker

Procedure

1.) Draw stripes across one sheet of paper, parallel to the short sides of the paper. The stripes should vary in spacing and thickness.
2.) Fold the paper in half lengthwise and write the word start at the top of both halves of the paper. Using the scissors carefully cut the paper in half along the fold line to form two strips.
3.) Lightly fold the second sheet pf paper into eights. The unfold it, leaving creases in the paper. Fold this sheet in half lengthwise.
4.) Starting at the fold, draw lines 5.5 cm long on the middle crease and the two creases closest to the ends of the paper.
5.) Now carefully cut along the lines you drew. Unfold the paper. There should be three slits in the center of the paper.
6.) Put the two striped strips of paper through so their start labels touch one another. Insert the start ends of the strips through the center slit and then pull them toward the side slits.
7.) Insert the ends of the strips and watch what happens at the center slit.
8.) Practice pulling the strips through the slits until you can make the two strips come up and go down at the same time.

Analyze and Conclude
1.) What feature of the ocean floor does the center slit stand for? What prominent feature of the ocean floor is missing from the model at this point?
The center slit stands for the Mid-Ocean Ridge, and the model is missing the molten material that passes through the Mid-Ocean Ridge.
2.) What do the side slits stand for? What does the space under the paper stand for?
The side slits stand for old crust sinking back into the mantle of the Earth. The space under the paper stands for the stands for the mantle itself.

3.) How does the ocean floor as shown by the part of the strip close to the center slit differ from the ocean floor as shown by the part near the side slit?
The ocean floor as represented by the part of the strip closer to the side slit is at a lower elevation than the ocean floor as represented by the part near the center slit.

4.) What do the stripes on the strips stand for? Why is it important that your model have an identical pattern of stripes on both sides of the center slit?
The stripes on the strips stand for the magnetic stripes located on the ocean floor, which indicates the reversal of the Earth’s poles. The stripes need to be identical on both sides of the strip because they represent stripes of a magnetic field which has a repetitive pattern.


5.) Explain how differences in density and temperature provide some of the force needed to cause sea-floor spreading and subduction?
Temperature from the mantle and core of the Earth can melt and unstable the ocean floor, letting the force of density push the plates away from eachother, causing the sea floor spreading.

6.) Think About It Use your own words to describe the process of ocean-floor spreading. What parts of the process were not shown in your model?
Sea floor spreading is a process in which plates of the Earth diverge to form trenches in the ocean floor. Through these trenches, molten material can flow through, continually adding new material to the ocean floor, a process that was not included in the model. Also not included in the model was the old crust being melted by the heat of the mantle.

MORE TO EXPLORE
Imagine that so much molten rock erupted from the mid-ocean ridge that an island formed there. How could you modify your model to show this island? How could you show what would happen to it over a long period of time?