Look at the pictures on the right. I took a piece of paper and cut a triangle in

Question

Look at the pictures on the right. I took a piece of paper and cut a triangle inside (Fig. 1). Now I have a model that is made up of two plates, A and B. In Fig. 2, I move my plate B in the direction marked by the arrow. Now imagine that these two plates are lithosphere, and that B is the more dense, while A is the less dense. Recall what you studied in the previous lessons (especially Lesson 2). If plate B moves relatively to plate A (i.e. the two plates are diverging), a “crack” must form along the ab side of the triangle, revealing “something” that lays beneath the lithosphere. Along the sides ac and bc of the triangle, the two plates are converging.

Now examine Fig. 3 and answer the following questions:

1. What can we see beneath the lithosphere in the shaded area?

A. the lithosphere; B. the asthenosphere; C. the lower mantle; D. earth's outer core;

2. What is forming along the ab side of plate B?

3. What is forming along the ac and bc sides of plate B?

4. What is the reason for your answers to questions 2 and 3? HINT: To answer the previous questions you have to focus on the direction of motion of plate B. For the purpose of this exercise plate A does not move. Also consider what you know about the “properties” of plate A and B, and recall what you studied. What happens when plates diverge or converge, or slide past each other? Which kind of boundary forms between the two plates as a consequence of a particular movement?

Explanation / Answer

1) asthenosphere

2)Along ab sidea ridge will form as the plates are diverging

3) as the density of plates vary, the more denser plate will subduct beneath the lesser one

4) B

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