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4.2: Earth's Magnetic Field

Difficulty Level: At Grade Created by: CK-12
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What would happen if Earth suddenly lost its magnetic field?

The most obvious effect is that we would get lost, since our compasses wouldn't work. Less obvious is that without the magnetic field the solar wind would strip away ozone from Earth's atmosphere and leave us exposed to ultraviolet radiation. Would life on Earth look the way it does now? Most, if not all, lifeforms couldn't survive.

Earth’s Magnetism

Earth is surrounded by a magnetic field (Figure below) that behaves as if the planet had a gigantic bar magnet inside of it. Earth's magnetic field also has a north and south pole. The magnetic field arises from the convection of molten iron and nickel metals in Earth's liquid outer core.

Earth's magnetic field is like a bar magnet resides in the center of the planet.

Magnetic Reversals

Many times during Earth history, even relatively recent Earth history, the planet's magnetic field has flipped. That is, the north pole becomes the south pole and the south pole becomes the north pole. Scientists are not sure why this happens. One hypothesis is that the convection that drives the magnetic field becomes chaotic and then reverses itself. Another hypothesis is that an external event, such as an asteroid impact, disrupts motions in the core and causes the reversal. The first hypothesis is supported by computer models, but the second does not seem to be supported by much data. There is little correlation between impact events and magnetic reversals.


  • Earth's magnetic field is like a bar magnet through the planet, with the south magnetic pole nearly aligned with the north geographic pole and vice versa.
  • The magnetic field is generated by convection in the liquid outer core.
  • Occasionally the magnetic field flips, with the north pole becoming the south pole and the south pole becoming the north pole.

Interactive Practice

Use this resource to answer the questions that follow.


1. What creates Earth's magnetic field?

2. What happens to the intensity and direction of the magnetic field according to the computer model?

3. What was studied in Oregon?

4. How do anomalies appear in the model?

5. What has been happening over the past 300 years?

6. How often has the magnetic field reversed, according to the research?

7. How long has it been since the last reversal?

8. How long does a reversal take to complete?


1. What would Earth's magnetic field be like if the planet was solid?

2. What roles does the magnetic field play for our planet?

3. How does the magnetic field resemble a bar magnet?

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magnetic field A field produced by a magnetic object that exerts a force on other magnetic materials or moving electrical charges. Earth's magnetic field behaves as if a magnet were contained within the planet.

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Difficulty Level:
At Grade
Date Created:
Feb 24, 2012
Last Modified:
Aug 07, 2016
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