Earth and space sciences Plate Tectonics

Despite appearances, the continents are not frozen in place but are constantly moving across the globe, breaking apart and colliding in slow motion. The driving forces are enormous and to understand them you need to delve deep below the surface of the planet.

This is a print version of an interactive online lesson. To sign up for the real thing or for curriculum details about the lesson go to www.cosmoslessons.com Introduction: Plate Tectonics

Our knowledge of how the world works is changing all the time. Only 40 years ago, scientists thought that the Earth's crust was 啜xed in place like the skin of an orange, but all that changed in 1963 with a paper written by Fred Vine. His 啜ndings were nothing less than a revolution in thinking about the structure of our planet.

Instead of being a solid skin, Vine said that the Earth’s surface was broken up like a jigsaw puzzle into large rigid slabs, called plates, that ꬃoated on the molten rocks and minerals that lay underneath. The incredible heat inside the planet made these plates constantly move, crash together, tear apart or grind past each other, Vine said. His theory is known as "plate tectonics". For the 啜rst time, this explained how great mountain ranges were formed and what caused earthquakes and created volcanoes.

Scientists also discovered major ridges deep below the surface of the world's oceans where magma – molten rock from the Earth's interior – rises up through cracks in the ocean ꬃoor. When it hits the cold water the molten rock hardens, adding new material to the ocean ꬃoor. The two plates on either side of these ocean ridges slowly spread away from each other as though they're sitting on a conveyer belt, always on the move.

The discovery also made scientists look again at the work of Alfred Wegener, a brilliant meteorologist and intrepid polar explorer. Back in 1915, he suggested that all the Earth's continents had once been joined together in a massive supercontinent called Pangaea. Because of plate tectonics, it gradually broke apart and the continents drifted to their current positions. But they didn't stop there and we now know that all the pieces of the puzzle are still on the move.

Read the full Cosmos Magazine article here .

Left: New ocean ꬃoor is continually being created from molten magma and moving away from the ridges like a slow-motion conveyer belt. Right: Meteorologist Alfred Wegener.

1 Question 1

Think: Do you have a mobile phone that uses GPS (Global Positioning System) to locate a speci啜c place? How will continental drift a訮ect the accuracy of the GPS?

Type your ideas here about how GPS technology may be useful to, or be challenged by, continental drift. Suggest possible solutions to overcome any challenges identi啜ed.

2 Gather: Plate Tectonics

0:00 / 2:13

Credit: Continental Drift | 100 Greatest Discoveries by Science Channel (YouTube).

3 Question 1

Notes: Use this space to take notes for the video.

Note: This is not a question and is optional, but we recommend taking notes – they will help you remember the main points of the video and also help if you need to come back to answer a question or review the lesson.

Question 2

Identify: What is the name of the supercontinent that Alfred Wegener thought existed hundreds of millions of years ago?

Question 3

Describe: List three di洅erent types of evidence that Wegener used to support his theory of continental drift and give a speci밄c example for each.

Evidence Speci褅c example

Question 4

Notes: Use this space to take notes for the video.

Note: This is not a question and is optional.

0:00 / 0:21

Credit: Plate tectonics animation by alex1234715 (YouTube).

4 Question 5

De褅ne: Write a de밄nition of plate tectonics.

Question 6

Identify: Which type of land formation is created when two land masses collide?

The diagram to the right shows the Earth's tectonic plates and their directions of movement. Use it to answer the question below.

Question 7

Draw: For each of the major tectonic plates named below, draw an arrow to indicate its direction of movement.

5 0:00 / 1:13

Credit: Earth – The Power of the Planet by BBC/Geo Dharma (YouTube).

Question 8

Notes: Use this space to take notes for the video.

Note: This is not a question and is optional.

Question 9

Describe: Write a step by step process to describe how tectonic plates move.

6 Process: Plate Tectonics

Above: The Himalayan mountains were formed as a result of the Indian Plate colliding with the Eurasian Plate.

Question 1

Calculate: If the Indo-Australian plate is moving at 7 cm per year, how long will it take to move 50 m?

350 years

350,000 years

7 years

714 years

I'm not sure

Question 2

Analyze: Watch the following silent animation of continental drift. Choose a country and write a 26-second commentary for this video to describe the movement of your chosen country. In your commentary describe the rate of movement and the position of your chosen country relative to other countries and continents.

Hint: A 26-second commentary is roughly equivalent to 60 words.

7 0:00 / 0:24

Credit: YouTube.

Question 3

Notes: Use this space to take notes for the video.

Note: This is not a question and is optional.

Question 4

Predict: Suppose you add cold blue water and hot red water to the same container so that they can interact. What do you expect to happen to the two bodies of coloured water given the temperature di洅erence between them?

Once you've made your prediction, watch the video below.

8 0:00 / 0:33

Credit: Water Density by Canada Science and Technology Museum (YouTube).

Question 5

Notes: Use this space to take notes for the video.

Note: This is not a question and is optional.

Question 6

Explain: Did your prediction match what you observed in the video? If not, explain how it was di洅erent and suggest reasons for the di洅erences.

Question 7

Compare: How does this experiment relate to the convection currents that cause the Earth's tectonic plates to move? What are the important di洅erences?

Hint: Where is the source of heat in the case of the Earth and what happens to the hot magma as it rises up to the crust?

9 Project: Plate Tectonics

Predicting a future map of the world

The dinosaurs were the dominant species 100 million years ago. What will the dominant species be 100 million years from now?

What will a map of the world look like in 100 million years? Where will Australia be? Where will the Americas be? Will there be any new major mountain ranges? How much bigger are the Himalayas going to be?

10 Question 1

Research: The following table summarizes the current motion of several major land masses (excluding Antarctica). The speeds are estimated averages relative to the African plate.

Use this information to complete the table. You will then be able to make predictions about how a world map would look 100 million years from now.

How fast is it Which land masses Land mass Which direction is it Which land masses moving? might it move away currently moving in? might it collide with? (cm/year) from?

India northeast 3

Australia northeast 7

Africa stationary 0

North America west 2

South America west 3

Eurasia south 1.2

Question 2

Predict: Drag and drop the major land masses shown below to imagine how a map of the world might look 100 million years from now. Indicate the locations of collisions between continents by drawing red lines.

11 Question 3

Justify: Describe the major changes that you've predicted in your future map of the world and justify your predictions.

Now sit back and enjoy this animation, which shows one model of how the modern continents evolved and how they might look in 100 million years. How closely do your predictions match the model?

0:00 / 3:18

Credit: Earth 100 Million Years From Now by SpaceRip (YouTube).

Question 4

Notes: Use this space to take notes for the video.

Note: This is not a question and is optional.

12 Career: Plate Tectonics

Sonya Pemberton is a Melbourne-based lm-maker who combines a passion for science communication with a talent for lm-making. Her documentaries tackle complex, controversial scientiගc issues, but the main inspiration for her work is that facts can be beautiful.

Sonya grew up in a family ගlled with curious minds and medical researchers. Her grandfather was an epidemiologist, her father specialized in providing medical care to newborn babies (neonatology), and her mother was a vivacious woman with a questing nature. When Sonya was growing up, her family encouraged her to think critically and it is perhaps this background that gives Sonya her talent for sniපng out the facts.

Sonya has hundreds of hours of experience writing, directing and producing content for TV. These days she works for a company called Genepool Productions, which specializes in creating interesting science television programs. Some of the issues that Sonya has explored include cervical cancer, immunization, DNA and mental illness. She is currently hard at work on new shows about autism, breast cancer, and nuclear power.

But making shows about science is not as straightforward as it may seem. Just imagine trying to make a ගlm about an organism that you can only see using a microscope!

Sonya says that to be a documentary ගlm-maker you need to be able to convey complicated information and controversial ideas in a way that engages people.

“My ගlms and I are both about the fact that being emotional and rational can co-exist; in a nutshell, that’s what everything I do is about.”

13 Question 1

Research: Sonya Pemberton is contributing to the ගeld of science without working as a scientist. Your task is to, through your own research, ගnd two other people that are contributing to the ගeld of science, but who do not work as scientists.

List the names of the people that you ගnd along with their job descriptions in the table below.

Person contributing to the eld of science Job description

Image credits

The Royal Society of Chemistry, iStock, Adobe Stock

14 Test: Plate Tectonics

Note: There may be more than one correct answer to the multiple-choice questions below.

Question 1 (1 mark) Question 2 (1 mark)

Alfred Wegener proposed a theory that he called Wegener noticed that the coastlines of several continents continental drift. This is the idea that the continents are seemed to 褅t together like puzzle pieces. For example, the not stationary but move around Earth's surface. east coast of South America 褅ts with the west coast of:

True North America

False South America

I'm not sure Europe

Africa

I'm not sure

Question 3 (1 mark) Question 4 (1 mark)

What was the fossil evidence that supported the theory of Wegener proposed that hundreds of millions of years ago continental drift? the world's land masses formed a single supercontinent. What did he call it? Fossils of land animals were found in deep ocean sediments Magma

The fossils of each continent were found to be Pangaea completely diㄆerent

Fossils of the same species and age were America found on continents now separated by oceans Atlantis Dinosaur fossils were discovered in Antarctica I'm not sure I'm not sure

15 Question 5 (1 mark) Question 6 (1 mark)

The theory of plate tectonics explains: Sometimes plates cause two land masses to collide. Which two processes are most likely to occur as a result? how life evolved Mountain-building how plates move around the Earth's surface Formation of a new ocean basin how the Earth formed Both land masses sink into the mantle why the Earth is divided into layers (core, mantle and crust) Earthquakes

I'm not sure I'm not sure

Use the diagram below to answer Questions 7, 8 and 9.

Question 7 (1 mark)

In which direction is the Eurasian Plate currently moving?

North

East

South

West

I'm not sure

Question 8 (1 mark) Question 9 (1 mark)

The Atlantic Ocean lies between the Americas on the west Which of these pairs of plates are colliding? and Europe and Africa on the east. It is currently: South American and African getting bigger as plates spread apart Indo-Australian and Antarctic getting smaller as plates move together North American and Eurasian staying the same size because it occupies a single stable plate South American and Nazca

I'm not sure I'm not sure

16 The diagram below right shows convection currents beneath two tectonic plates. Use it to answer Questions 10, 11 and 12.

Question 10 (1 mark)

The rock at Point A is:

cool and rising

cool and sinking

hot and rising

hot and sinking

I'm not sure

Question 11 (1 mark) Question 12 (1 mark)

The rock at Point C is: The rock at Points B and D is moving horizontally causing Plates 1 and 2 to: cool and rising collide cool and sinking drift apart hot and rising slide past each other hot and sinking stay motionless, because the forces are I'm not sure balanced

I'm not sure

Question 13 (1 mark)

The diagram on the left shows how volcanoes are typically formed close to plate boundaries as the descending plate heats up and melts.

Which other typical geographical feature is shown?

A high mountain range where two land masses have collided

An ocean ridge where two plates are spreading apart

A deep ocean trench where one plate is sinking beneath the other

I'm not sure

17 Question 14 (1 mark) Question 15 (1 mark)

Alice lived in the same Australian town her whole life Assuming that plate tectonics will continue then a map of before she died, aged 80. If Australia is moving northward the world 1 billion years from now would probably show: at about 7 cm per year, how far did Alice's home town move during her lifetime? the same continents we have today in roughly the same positions 56 cm the same continents we have today but moved 5.6 m about 100 metres in diㄆerent directions a radically diㄆerent arrangement of continents 560 m and oceans

5.6 km a vast ocean with no continents, because continents tend to sink at plate boundaries I'm not sure I'm not sure

Question 16 (1 mark)

Learning goal 1: You're talking to a young child who doesn't believe that continents can move. What would you say to convince them that continental drift is real?

Question 17 (1 mark)

Learning goal 2: The South American Plate and African Plate are spreading apart. Explain why this is happening in terms of the movement of rock beneath the two plates.

Question 18 (1 mark)

Learning goal 3: The Himalayan mountains formed when India collided with Asia. Describe how this happened in terms of the movements of the Indo-Australian and Eurasian Plates and explain why it created the highest mountain peaks in the world.

Hint: The world map of tectonic plates beside Question 7 might be helpful.

Total available marks: 18

18