Earth Science Chapter 5 Plate Tectonics

Big Ideas Earth’s Interior Convection and the Mantle Drifting continents Sea-floor Spreading Plate Tectonics

Earth’s Interior How far do you think it is to the center of the Earth?

Almost 4,000 miles! The deepest mine in the world is only 2 miles

How do you think scientists know about the center of the Earth?

Geologists use 2 main types of evidence to learn about Earth’s interior: – Direct Evidence from rock samples – Indirect evidence from seismic waves

Evidence from Rocks Humans have drilled holes and extracted rock from depths of 12 miles Blasts from the Earth have brought rocks from 100 ft to the surface

Evidence from Seismic Waves Earthquakes produce seismic waves The speed of seismic waves and the path they take show the structure of the planet

Three main layers The three main layers of Earth are the crust, mantle, and the core These layers differ in size, composition, temperature, and pressure

Temperature The first 20 meters beneath Earth’s crust is cool After this depth, temperature rises 1 degree Celsius per 40 meters Heat comes from the molten layer and radioactive substances

Pressure The deeper you go, the higher the pressure This pressure is equal to that of a swimming pool

Pressure

Lab Skills Activity Work with a partner, Read the directions to the Lab Zone Skills Activity Create the Data Table on page 129

Crust Crust is a layer of rock that forms Earth’s outer skin Crust includes both dry land and ocean floor Crust is very thin compared to the other layers of Earth, only 5-70 km thick

Crust

The crust beneath the ocean is oceanic crust and usually made of basalt Continental crust consists of rocks such as granite

I was very disappointed in the behavior of some of you on Friday. That was extremely disrespectful of you to run from the classroom when the bell rang. You need to remember that I dismiss you and not the bell. Please take your seat and sit quietly while you wait for class to begin

Mantle The mantle is about 40 km below the surface It consists of a hot, solid rock It can be divided into layers The mantle is about 3000 km thick

Mantle

Lithosphere The crust and the uppermost part of the mantle form the lithosphere It is about 100 km thick Lithos means “stone” in Greek

Lithosphere

Asthenosphere Under increase heat and pressure Less rigid-soft like tar, but still solid Asthenes means “weak” in Greek

The Lower Mantle Beneath the asthenosphere the mantle is solid This material extends to the Earth’s core

Lower Mantle

The Core Consists of mostly nickel and iron Made of two parts, a liquid outer core and solid inner core Together it is about 3486 km thick

Despite extreme pressure, the outer core is molten surrounding a dense, solid inner core Evidence suggests that the extreme pressure in the inner core will not allow the solid metal to spread and become liquid

Core

Core and Magnetic field Scientists think that movements in Earth’s liquid outer core create Earth’s magnetic field. This magnetism is what attracts a compass’ needle towards north (it aligns with Earth’s magnetic field)

Individually Complete the section 1 assessment on page 131, including the “writing in science” assignment. If you do not complete these in class, they will become your homework and will be due tomorrow.

Make a Chart Types of Heat Transfer Radiation Explanation/definition Conduction Explanation/Definition Convection Explanation/Definition

When you complete the chart Read the sections “Convection Currents”, and “Convection Currents in Earth.” 1. Define Convection Currents 2. Explain how convection currents work, using a real example 3. Create an illustration of a convection current

Bellwork What are the three types of heat transfer and give an example of one that is not in your book!

Drifting Continents dXPA dXPA

Continental Drift Prior to Columbus, mapmakers did not know about the new worlds Shortly after they began to notice how the coastlines of several countries seemed to fit together like a puzzle

Continental drift Early 1900s German Scientist Alfred Wegener made a hypothesis: All of the continents were once joined together in a single land mass and have since drifted apart.

The Origin of Continents and Oceans Wegener gathered evidence from different scientific fields to support his ideas about continental drift. He studied land features, fossils, and evidence of climate change

Write a Book! Make your own version of Wegner’s book Use the same title as he did Read pages about the evidence he found Create a page for each type of evidence Explain how the evidence supports his hypothesis and include illustrations if appropriate.

The Origin of Continents and Oceans Page 1: Title Page 2: Evidence from land features Page 3: Evidence from fossils Page 4: Evidence from climate Page 5: Conclusion

WHAT DID YOU FIND ?

Sea-Floor Spreading PYh4 PYh4

Mid Ocean Ridges

Mid Ocean Ridge Curve like seams through Earth’s oceans Most mountains are under water, except Iceland!

Iceland

Hess and Sea-floor spreading Harry Hess in 1960 realized that Wegener was right and the continents were being moved by sea-floor spreading: – The sea floor spreads apart along both sides of a mid-ocean ridge as new crust is added – The ocean floors act like conveyor belts carrying the continents along with them

Read pages

Editorial You are Harry Hess! (or Harriet Hess) You have just concluded your research about sea-floor spreading Prepare a speech for your science conference in which you will share your findings Include your theory, the evidence that supports if from molten material, magnetic stripes, and drilling samples, and end with a conclusive argument!

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Bellwork What were the three types of evidence Harry Hess used to support his theory of sea floor spreading?

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11-19 Activity Open your books to page 148 We will be completing this lab activity in class today Everyone needs to complete their own sea- floor spreading model When you complete the model you will answer the Analyze and Conclude questions You may talk to students near your desk about the questions 1-6

When you complete the activity, Come up with two original questions from each of the four sections in this chapter (make sure you can answer your question) I will combine these questions for your review session tomorrow!

Subduction at Trenches Deep-ocean trenches: deep underwater canyons. At deep-ocean trenches the oceanic crust bends down and sinks beneath the continental crust.

Subduction Subduction: the process by which ocean floor sinks beneath the deep ocean trench and back into the mantle

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Process of Subduction As the older rock is subducted, younger rock moves away from the mid-ocean ridge New rock is hot, but it cools and becomes more dense as it ages

Old rock, New Rock, Red Rock, Green Rock

Process Continued Eventually gravity pulls the older, denser rock down at the trenches

Subduction and Earth’s Oceans Subduction and seafloor spreading can change the size and shape of the oceans Ocean floor is renewed about every 200 million years The Pacific’s trenches are eating more crust than the ridges can make In the Atlantic the opposite is the case

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