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Overview:
This lesson will provide students with information about how islands are formed, including a basic knowledge of plate tectonics. Using the islands of Hawaii as an example, students will learn about the earth processes that cause the formation of islands over time, including volcanoes and "hot spots."
Connections to the Curriculum:
Geography, geology
Connections to the National Geography Standards:
Standard 4: "The physical and human characteristics of places"
Time:
Two to three hours
Materials Required:
- Computer with Internet access
- Marshmallows and chocolate, or hard-boiled eggs, for demonstration
- Writing and drawing materials
Objectives:
Students will
- learn the basic scientific ideas behind plate tectonics and continental drift;
- think about how these principles help shape our understanding of island formation;
- learn about how islands are formed; and
- create a presentation based on a specific aspect of island formation.
Geographic Skills:
Asking Geographic Questions
Acquiring Geographic Information
Organizing Geographic Information
Answering Geographic Questions
Analyzing Geographic Information
S u g g e s t e d P r o c e d u r e
Opening:
Ask students what they know about islands. Have they visited islands? What are islands? Do students know how they are formed? Write their ideas on the board or on a large piece of paper.
Explain that islands are areas of land surrounded entirely by water, and that while we usually think of islands in the ocean, they also exist in rivers and lakes.
Development:
Introduce to students the theories of plate tectonics and continental drift with a simple, hands-on experiment.
Melt chocolate in a pot or a microwave and have students dip marshmallows into the chocolate. Allow to cool and harden. Have students squeeze their marshmallows and ask them what happens. The chocolate should crack, simulating the Earth's crust (lithosphere) cracking. [Note: Another option is to use a hard-boiled egg; when it is gently squeezed, the shell cracks like the Earth's crust.]
Explain that the cracked chocolate (or eggshell) is like the land masses on Earth that move slowly over long periods of time, forming the continents and islands.
In small groups, have students explore the following questions:
- How are islands formed? Is there just one way, or are there several different ways?
- How are islands distributed around the world? Can you explain why they form where they do?
- Over what time periods are islands formed? Decades? Centuries? Millennia?
- How do the geological and geographical features of islands affect the people who live on them? For example, are there extreme weather conditions?
The following Web sites will help students answer the questions:
National Geographic: Expedition—Dangerous Archipelago
National Geographic: Xpedition Hall—Big Island Pool
Atolls and Reefs
Brain Pop: Science (search for these movies: Ocean Floor, Plate Tectonics, Earth's Structure, and Volcanoes) [Note: Without a paid subscription, you can only watch two videos per day.]
PBS: NOVA Online—Garden of Eden (especially the Build an Atoll activity)
Tuamotu Islands
Closing:
Ask students to think about what they have learned in this lesson and decide whether they think they would like to live on an island (assuming they don't already!). Why or why not? Do they think more islands will be formed on Earth in the future?
Suggested Student Assessment:
Ask students to choose one aspect of island formation that they find particularly interesting. Examples include how an atoll is formed, weather systems around islands, or the volcanic formation of islands. Either individually or in small groups, ask students to illustrate and write an accompanying narrative explaining this specific aspect of island formation.
Extending the Lesson:
There are many legends that describe how the Hawaiian islands were formed. Have students write their own fables or fairy tales about how a chain of islands was formed.
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