How can you find your way?
You can use Earth's magnetic field to tell you where you want to go. A compass needle aligns with Earth’s magnetic field. People can navigate by finding magnetic north. If you know where north is, you can figure out how to get anywhere. A compass is great for finding your way when you're out in the field!
Earth has a magnetic field (Figure below). The magnetic field behaves like a giant bar magnet inside Earth. If you have a large bar magnet, you can hang it from a string. Then watch as it aligns itself in a north-south direction. It does this to line up with Earth’s magnetic field.
Earth's magnetic field is like a bar magnet that resides in the center of the planet.
The magnetic field has north and south poles. The magnetic poles do not exactly match the geographic poles. So the North Magnetic Pole is not the same as the geographic North Pole. The same is true of the South Pole. The magnetic field is created by the movement of molten metal in the outer core.
Earth's magnetic field protects the planet from harmful radiation.
Something very strange has happened many times during Earth's history. The planet's magnetic field flipped! The North Magnetic Pole became the South Magnetic Pole. The South Magnetic Pole became the North Magnetic Pole. Scientists are not sure why this happens. The fact that it does happen is useful to scientists. In the chapter Plate Tectonics, you'll learn how.
- Earth's magnetic field is like a bar magnet through the planet.
- The magnetic field is generated by convection in the liquid outer core.
- Occasionally the magnetic field flips. The North Magnetic Pole becomes the South Magnetic Pole and the South Magnetic Pole becomes the North Magnetic Pole.
Use the resource below to answer the questions that follow.
- 100 Greatest Discoveries: Earth's Magnetic Field at http://science.howstuffworks.com/environmental/29143-100-greatest-discoveries-earths-magnetic-field-video.htm (2:34)
- What aligns itself with the magnetic field in molten rocks as they cool?
- What did Brunhes discover about some of the rocks?
- What did Brunhes' discovery mean?
- What has happened to the magnetic field in the last century and a half?
- What planet is being studied to discover the future of Earth without a magnetic field? What is this planet like without a magnetic field?
- Why does Earth have a magnetic field?
- Why is it important for Earth to have a magnetic field?
- What is a magnetic field reversal?