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Science 10: 12.2 Features of Plate Tectonics

Text: Chapter 12, pages 506-517

Part A: Earth’s Interior Introduction

-Less than 100 years ago scientists had to use the features at Earth’s surface to infer what existed in its interior.

-What features would you use to support the idea that Earth’s interior is not just a solid mass of rock?

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-We now know that as Earth cooled after its formation dense materials sunk to its interior and less dense materials floated on top, creating different layers.

Part B: Earth Cross Section

-There are four distinct Earth layers:

1. Crust:

-Outermost and thinnest layer. Continental is granite, oceanic is basalt.

2. Mantle:

-Thickest layer and accounts for 70% of Earth’s volume.

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-Upper Mantle, partly molten rock rich in iron and magnesium. Is plastic (solid that can flow)

-Lower Mantle: Solid, dense and rich in iron and magnesium.

3. Outer Core:

-Liquid, made of iron and nickel.

4. Inner Core:

-Earth’s centre. Made of mostly iron and some nickel. High pressure makes it solid despite hot temperatures (5000 to 6000 °C).

Part C: Tectonic Plates

-There are about 12 tectonic plates and they can be composed of two types of materials. What are they?

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-The upper portions of the mantle and crust can further be subdivided into two separate layers:

1. Asthenosphere:

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2. Lithosphere:

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-Two which of the layers above do the tectonic plates belong?

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Part D: Tectonic Plate Motion

-Where do you think the heat that keeps the asthenosphere molten is coming from?

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-Explain how the addition of heat to the asthenosphere generates convection currents.

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-Convection currents are one of the driving forces behind the movement of tectonic plates. Other contributing factors include:

1. Ridge Push:

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2. Mantle Drag:

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2. Slab Pull:

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Part E: Tectonic Plate Interactions

-Plate boundaries are where two tectonic plates interact. There are three main types:

1. Divergent

-What type of plate movement is occurring here?

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-Rift valleys become mid-ocean ridges given enough time.

-Mid-Atlantic Ridge is the longest mountain chain in the world.

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2. Convergent

What type of plate movement

occurs here?

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-Type of convergent boundary depends on the composition of the colliding plates:

a) Oceanic-Continental Plate Convergences

-Which of the two plates colliding here would subduct? Why?

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-What features are formed by this type of plate interaction?

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b) Oceanic-Oceanic Plate Convergences

-If both plates are made of the same material (basalt), why does one subduct?

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-What type of features will be formed?

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c) Continental-Continental Plate Convergences

-When two continents collide, why does one plate not subduct?

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-What type of features form from this collision?

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3. Transform

-How is this plate boundary different from the others we have looked at?

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-What features would be produced by this type of interaction?

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*Below is a summary of plate tectonic interactions:

Part F: Earthquakes

1. Earthquake Formation

-Friction between interacting plates can create stress (the build-up of pressure).

-When the stress gets too great the plates slip and release the stored energy.

-What is the difference between the Focus (Hypocentre) and Epicentre?

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-Examine the map right. Where would the deepest focus be found?

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-What depth of Earthquake do you think will cause the most damage? Why?

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2. Seismic Waves

-Energy released from earthquakes travels outwards from the focus as waves. There are three types:

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-Seismic waves have been very useful to scientists in revealing the nature of Earth’s interior. For example, seismic waves speed up as they descend into the mantle, which indicates that the mantle’s density is increasing with depth.

3. Measuring Earthquakes

-Seismometers measure the amount of ground motion, the time of earthquake and how long it lasted.

-Earthquakes are measured by magnitude, with a 10x increase in magnitude between numbers on the Richter Scale.

-How much stronger is a magnitude 9 earthquake than a magnitude 5?

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*Try 12-2C: Interpreting Seismograms

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Part G: Volcanoes

-The movement of tectonic plates cause three main types of volcanoes: Composite, Shield and Rift.

-With a partner, you will select one volcano type and research a specific volcano of that type (You will need to get this approved by Mr. Fox). You will create a small presentation that must cover the following points:

1. Name and location of your volcano.

2. Type of tectonic plate boundary your volcano is associated with. You should discuss the nature of this boundary.

3. Discuss your volcanoes distinguishing features.

4. Relate the type of plate boundary and magma/lava created to the shape/characteristics of your volcano (if applicable).

*Make sure that you take your own notes on all three volcano types from the text!

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