Why Is the Earth Like a Magnet?

The protective influence of the Earth's magnetic field has promoted the development of life on the planet. It is very difficult to study the origins of this magnetic field. However, using measurements of the field that have been taken over the past 150 years, scientists have been able to deduce the most probable causes of the Earth's magnetism.

Function

The Earth's core is made of solid metal. This core is surrounded by a molten outer core composed primarily of nickel and iron. Convection causes the liquid metal to flow very quickly, creating electrical currents that produce the Earth's magnetic field. This is called the "dynamo effect."

Features

The magnetosphere is an important by-product of the Earth's magnetic field. It extends around the Earth up to thousands of miles over the surface. The solar wind, a stream of charged particles that continuously flows from the corona of the sun, distorts the magnetic field as it passes around the Earth. The magnetosphere helps to protect the Earth from the solar wind.

Effects

Compass needles point north because the Earth has a magnetic field. This facilitates navigation when physical landmarks are few or absent. However, the magnetic north pole and the true north pole are not in the same place. In fact, the magnetic north pole can move up to 25 miles per year. The Van Allen radiation belts are produced when charged particles from the solar wind become trapped in the Earth's magnetic field. Animals such as birds can use the Earth's magnetic field to guide them during periods of migration.

Theories/Speculation

One common theory is that the Earth's magnetic field occasionally reverses itself. The strongest part of the field wanes, but the weaker side of the field remains. After this process completes itself, the north pole will be the south pole. This "flipping" of the Earth's poles doesn't happen often or regularly. The poles last reversed around 780,000 years ago. We are currently undergoing another reversal, but it may take thousands of years to complete.

Time Frame

A study at the University of Rochester showed that the Earth's magnetosphere was already in existence 3.2 billion years ago. This is 500 million years before the Earth's magnetic field was previously believed to have formed. The scientists used ancient pieces of feldspar and quartz from South Africa to complete this study. They inspected the rocks for tiny traces of magnetite, which can survive for billions of years because it is shielded by silicates.