To explore plate tectonics and to understand how mountains, earthquakes, and volcanoes are related to the movements of plates.
Leading up to high school, students have obtained a descriptive understanding of the physical factors that shape earth. They know about the heat flow and movement of material within the earth that causes abrupt volcanic reactions and earthquakes. Also, that this movement of hot material within the earth causes other changes on earth's surface, such as the uplift of mountains and valleys.
In this lesson, students will learn about the idea of continental drift and the theory of plate tectonics to ascertain a fuller picture of how land formations on earth's surface are shaped by plates moving below the surface.
It would be helpful to your students if a large world map or globe is placed at the front of the class for them to refer to at various times during the lesson.
Begin the lesson by asking students if they can imagine experiencing an earthquake. Briefly discuss what it might be like: things flying off of shelves, broken glass, collapsed highways, etc. Have students read the first two pages of Remembering Loma Prieta at Faultline.
Discuss what caused the great quake in California, using the following guiding questions:
- What is the San Andreas fault?
(The boundary between two giant blocks of the earth's crust: the Pacific Plate to the west and the North American Plate to the east.)
- How did the plates cause the earthquake?
(The Pacific Plate is slowly pushing its way north, but it gets hung up in places. After a time, the strain becomes too much and the two plates lurch past each other in a violent release.)
- Can you think of other examples where there is a strain between two things that results in a violent release?
Research suggests that some students may not be aware of the changes that occur on earth's surface, or may be unaware of the slower, ongoing changes, such as the uplift of a mountain. (Benchmarks for Science Literacy, p. 336.)
The following questions are intended to set up the lesson and establish students' level of awareness regarding these concepts. Although the experiences in this lesson are designed to help correct this misconception, some students may require more opportunities for instruction and assessment than are presented here.
Have students answer the questions in their science journals. At the end of the lesson, they will be provided with an opportunity to revise their answers. You may wish to write the questions on the board and refer to them throughout the lesson:
- What happens underneath the surface of the earth? Can you describe it?
- What are the plates found in the earth's crust? How do you think they move? How many are there?
- What kinds of things do you think these plates can cause on the earth's surface? Give some examples?
At Earthforce's website, have students read the first article, Earthforces in the Core.
After reading the article, have them draw a diagram of the layers of earth in their notebooks. Their diagrams should look something like the diagram at Earth's Interior. They should label inner core, outer core, mantle, lithosphere, and crust, which is the upper part of the lithosphere. Discuss what these layers are made of and have them write this on their diagrams.
When the diagrams are finished, ask:
- Which layer are the plates in?
- Which layer do the plates "float" or move on?
- How do you think the moving plates affect the layer of earth above them?
Tell students to save their answers to these questions as they will revise them based on their explorations of earthquakes.
Back at Earthforces, have students read the second article, Earthforces in the Crust. Ask them to write the definition of plate tectonics in their notebooks and to list some results of the pushing and pulling of the plates.
At the Faultline site, have students read Plate Tectonics. When students finish reading, break them into groups of two or three. Direct them to take a look at The Breakup of Pangaea, which has maps depicting continental drift. Have each group sketch and cut out the continents as they exist today. They can use the picture labeled "present day" as a guide.
If time allows, have them label the continents using the map at the front of the room. Once the continents are cut out, have students put them together as pieces of a puzzle, or Pangaea (the supercontinent). Then, have students break the continents apart as Wegener's theory states. They can use the maps on the computer as a guide. Eventually, students should spread the continents back out to the present day. In their notebooks, have students describe continental drift and where the theory originated.
Now have students read Faults and record in their notebooks, with diagrams and descriptions, the three types of faults.
Ask if anyone knows where the world's highest mountains are located. Students may be familiar with Mt. Everest, the highest of the Himalayans because of recent books and movies about crews climbing the behemoth. On your map of the world, point out the Himalayans. Ask if anyone knows how these mountains grew to be so high.
After students have read the article, ask them these questions to lead a discussion:
- How tall is Mt. Everest? Has it always been the same height? If not, is it still growing? At what rate is it growing?
- How was Mt. Everest formed?
- Do you think earthquakes occur in the Himalayan's?
To assess students' understanding, provide them with an opportunity to revise their answers to the questions from the motivation section of the lesson. (1. What happens underneath the surface of the earth? Can you describe it? 2. What are the plates found in the earth's crust? How do you think they move? How many are there? 3. What kinds of things do you think these plates can cause to happen to earth? Can you give some examples?)
Ask them to describe how their ideas about the plates changed and why.
To help students build a fuller picture of how land formations on earth's surface are shaped by plates moving below the surface, ask students to think about what the Himalayan mountains have in common with earthquakes. Have students write a one-page essay to answer the question. This exercise should help students see that plate tectonics can have two very different outcomes on earth's surface.
One way to reinforce what has already been learned in this activity is to bring volcanoes in as an extension. When plates move and magma finds an escape from underneath, the result is a volcano.
Volcanoes is one of several forces of nature online interactives from National Geographic. Students can learn about the different types of volcanoes, where they occur, how they form, and even make their own volcano erupt online!
Discuss the similarities or differences between earthquakes and volcanoes.
- How are the plate movements different or the same?
- How are the processes of the two different or the same?
- How are the outcomes on the surface different?
To see images of volcanoes, go to Volcano World.