- How volcanoes form
- Volcanoes at divergent and convergent plate boundaries
- Volcanic hot spots
- Explain how volcanoes form.
- Describe places where volcanoes occur.
- Describe what volcanic hot spots are and where they occur.
fissure: crack in the crust at a divergent plate boundary where magma may erupt
hot spot: place where a plume of hot molten rock rises through the mantle and may cause volcanoes
mantle plume: column of hot molten rock that rises through the mantle
Introducing the Lesson
Have students look at the chapter opener photo of the 2010 volcanic eruption in Iceland, and ask them to read the opening paragraph. Tell the class that the intense volcanic activity resulted in the biggest disruption of air travel since World War II. Ask students why they think air travel was disrupted by the volcanic eruptions. (Airlines feared that the thick clouds of ash would ruin airplane engines.) Tell students they will learn what causes volcanoes such as these when they read this lesson.
Building Science Skills
Use the activity “Gelatin Volcanoes” at the URL below, in which students will model a volcano to understand how and why magma moves inside volcanoes. The activity was inspired by a series of experiments using gelatin models, which were conducted by researchers in the 1970s to explain the growth and orientation of Hawaiian rift zones. In the activity, gelatin molded in bowls or bread pans is used as transparent models of volcanic landforms. Colored water is used as magma.
Make sure students understand how most volcanoes occur. Ask them to create a drawing showing how volcanoes occur in subduction zones around the Pacific Ocean, where the edge of the Pacific plate sinks beneath continental crust. Have them explain their drawing to you, and help them add appropriate labels. Suggest that they save their drawing in their science notebook. This is a good activity for kinesthetic and visual learners as well as English language learners and less proficient readers.
Ask a few students who need extra challenges to look in greater depth at Icelandic volcanoes, which are used as an example in the opening to the chapter. Suggest that students find answers to questions such as those listed below. Then have them report back to the class on what they learn.
- What tectonic plate activity explains these volcanoes?
- How many volcanoes are there?
- How active are the volcanoes?
- What is it like to live in a land of active volcanoes?
In the activity “Surrounded by Volcanoes” at the URL below, students will recognize individual Cascade volcanoes as part of an extensive volcanic mountain range and as part of the Pacific Ring of Fire. They will also draw conclusions about relationships between plate movements and volcanic activity.
Use the following three common student misconceptions about volcanoes as a true-false quiz. Discuss as a class any misconceptions that students think are true. Make sure students understand why volcanoes are found where they are. These and other misconceptions about volcanoes are discussed at this URL: http://beyondpenguins.ehe.osu.edu/issue/earths-changing-surface/common-misconceptions-about-weathering-erosion-volcanoes-and-earthquakes.
- Volcanoes are randomly located across the earth’s surface.
- Volcanoes are found only on land.
- Volcanoes are found only in hot climates.
Reinforce and Review
Copy and distribute the lesson worksheets in the CK-12 Earth Science for Middle School Workbook. Ask students to complete the worksheets alone or in pairs to reinforce lesson content.
Lesson Review Questions
Have students answer the Review Questions listed at the end of the lesson in the FlexBook® student edition.
Check students’ mastery of the lesson with Lesson 8.1 Quiz in CK-12 Earth Science for Middle School Quizzes and Tests.
Points to Consider
When you look at the map of tectonic plates, what areas besides the Pacific Ring of Fire would you expect to have volcanic activity?
Why do you think some volcanoes are no longer active and probably never will be again?
Why do you think it’s hard to study hot spots?