Earth’s magnetism
- 2. Magnetic FieldsMagnetic Fields As you probably already know theAs you probably already know the planet Earth is like one giant magnetplanet Earth is like one giant magnet with a north and a south pole.with a north and a south pole. It is believed that this magnetic fieldIt is believed that this magnetic field is caused by the movements of theis caused by the movements of the Earth’s outer core fluid which isEarth’s outer core fluid which is composed of mostly iron and nickel.composed of mostly iron and nickel.
- 3. Did you know?Did you know? The planet Earth has undergone severalThe planet Earth has undergone several magnetic reversals, or a time when themagnetic reversals, or a time when the magnetic fields were reversed. Thismagnetic fields were reversed. This theory is known as the Dynamo Theory.theory is known as the Dynamo Theory. Scientists know this from studying theScientists know this from studying the alignment of atoms in iron formed fromalignment of atoms in iron formed from cooled magma. The device used is calledcooled magma. The device used is called a magnetometer. It allows scientists toa magnetometer. It allows scientists to determine the direction of the Earth’sdetermine the direction of the Earth’s magnetic field at the time the rock wasmagnetic field at the time the rock was formed.formed.
- 4. Sea Floor SpreadingSea Floor Spreading
- 5. Another LookAnother Look As molten rock rises, spreads out and cools, magnetized minerals record field direction Over millions of years, the seafloor rocks retain a 'barcode' of pole reversals These pole reversal events may take perhaps 10,000 years to complete The last major pole flip appears to have been about 780,000 years ago