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Connect: What is different about this world map to the world map we see today? What could the reason be for these changes? Discuss with the person sitting by you.

Lesson 2 of 2: Why is the earths crust unstable? 1. By looking at the structure of the earth. 2. By exploring how plate tectonics influence the stability of the earth.

Big Picture: How do plate tectonics influence the stability of the earth? 1. Know that the earths crust is broken into different types of crust 2. Describe the different types of plate margins. 3. Evaluate why the earths crust is unstable especially at plate margins.

How is the earths crust split up into different types of crust? There are 2 types of crust. • 1. Oceanic Crust: Thin crust that lies over the ocean. • 2. Continental Crust: Thick crust that lies over land

Activate: Use the missing words to complete the definitions of oceanic and continental crust.

Continental dense

Oceanic thin thicker land

• _________ crust is ________ crust that lies under the oceans. • ___________ crust is the thinner (more ______) crust that lies over.

• Extension: Which crust do you think has more volcanic activity? Why do you think this ?

So…The difference between continental and oceanic crust • Continental crust is thicker and less dense. • Oceanic crust is thinner and more dense. • Oceanic crust is younger than continental crust.

What is a plate margin?

What is a plate margin? The oceanic and continental crust is split up into different plates. These are known as the plate margins or plate boundaries.

Task. Copy this definition or write your own definition of what a plate margin is into the box.

Task: Watch the video clips to answer the questions about plate margins. • dTk • Gx8 • H6Q

Demonstrate: Why do you think the earths crust is unstable?

Follow the instructions to answer the questions. • 1. How strong do you think the egg is where it has been cracked? • 2. What would happen to the egg shell if these plates were to collide (move together)? • 3. What would happen to the egg if these plates were to move apart? • 4. Relate this to the structure of the earth. Write a paragraph to answer: Why is the earth’s crust unstable. KEY TERMS: crust, plate, plate

margin/boundary, mantle, convection currents.

Reflect • Think about what you learnt last lesson (the structure of the earth) and reflect on what you have learnt today. • In no more than 20 words answer: Why is the earths crust unstable?

restless earth, 2  

restless earth, 2

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