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What is a Dormant Volcano? - Definition, Facts & Example

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  • 0:01 Types of Volcanoes
  • 1:33 Energy Source
  • 2:24 Five Dormant Volcanoes
  • 3:46 Lesson Summary
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Lesson Transcript
Instructor
Kimberly Schulte

Kimberly has taught at the university level for over 17 years.

Expert Contributor
Maria Airth

Maria has a Doctorate of Education and over 20 years of experience teaching psychology and math related courses at the university level.

Did you know some volcanoes can ''sleep'' for thousands of years while others erupt at regular intervals? In this lesson, we will learn why some volcanoes can wait long periods of time before erupting. We will also look at some examples of dormant volcanoes.

Sleeping Giants

Volcanologists (geologists who study volcanoes) classify volcanoes as either active, dormant, or extinct. An active volcano is a volcano that is currently erupting or has erupted recently, such as Mount St. Helens, which most recently erupted in 1980.

A dormant volcano is one that has not erupted recently but is expected to do so again. Prior to its 1980 eruption, Mount St. Helens had been classified as dormant.

An extinct volcano is a volcano that volcanologists do not think will ever erupt again, such as Mount Buninyong in Australia.

It is often difficult to determine which volcanoes are extinct and which are dormant. The reason for this is volcanoes can go decades, hundreds of years, or even hundreds of thousands of years before they erupt. Even the experts can't agree on the difference.

Some volcanologists have classified volcanoes as dormant that have not erupted in the last 10,000 years. The cutoff of 10,000 years is used because it marks the end of the last ice age and the beginning of the Holocene Epoch. While the 10,000-year mark gives an easy way to distinguish between active and dormant volcanoes, not all volcanologists are in agreement on this cutoff. Other volcanologists consider volcanoes that have erupted in historical times to be active. However, the term historical times is somewhat arbitrary and can vary, depending on what part of the world you are investigating.

Energy Source

All volcanoes are fed by and get their energy from magma, molten rock coming from the Earth's mantle. Dormant volcanoes still have access to magma, while most extinct volcanoes do not. This is due to shifting tectonic plates. As the plates move, the volcano moves off the hot spot, or magma source. When this happens, the volcano is cut off from the magma source. Typically, a new volcano can form over the hot spot.

Another way to look at this is to use a car as an example. If you have a tank full of gas but the car is parked in the driveway, it still has access to its energy source. This is evident when you start the car to drive away. However, if the car is empty and you never put gas in the car again, it will never run. The car, just like the volcano, must have access to its energy source.

Five Dormant Volcanoes

While there are numerous dormant volcanoes found all over the world, some of the more notable include the following:

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Additional Activities

Research Activity

In this activity, students will conduct a case study of a specific dormant volcano.

Reflection Discussion

  • After reviewing the lesson, students should discuss:
    • Why do some volcanoes go dormant?
    • Is a dormant volcano safe?
    • How can volcanologists know whether a dormant volcano will or won't erupt again?
    • How can they know when a volcano last erupted?
    • What dormant volcanoes do you know about (that aren't listed in the lesson)?

Dormant Volcano Case Study Assignment Instructions

  • Instruct students to research other dormant volcanoes and choose one on which to focus. This should not be one of those mentioned in the lesson.
  • Now, students should take time to research their chosen volcano and write a report answering these questions:
    • Where is it?
    • What is its name?
    • What type of geological manifestation has it taken on (for example, it could be a full island or a lake)?
    • Are there people living on or near it?
    • When is it supposed to have erupted last?
    • How do scientists know when it last erupted?
    • Is it an important part of the culture in its region?
    • (Speculation) What might be the consequences if it were to suddenly erupt again?

Extension

  • To extend this assignment, instruct students to prepare a brief oral presentation based on the information they have learned.
    • The presentation should include all of the previous information as well as at least one visual aid related to the chosen dormant volcano.

Alternative

  • If necessary, students may research one of the mentioned dormant volcanoes in the lesson. However, they must include more information than given in the lesson in their report and/or oral presentation.

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