The document discusses the Earth's magnetic field and magnetic polar reversals. It explains that the field is generated by convection currents in the Earth's liquid outer core, known as the geodynamo. The magnetic poles have changed positions many times throughout history, as evidenced by the magnetic orientations locked in ancient lava and rock. While a reversal takes thousands of years, the magnetic field does not disappear completely during this process. The current field protects life on Earth from solar radiation.

1. A Brief Guide To Magnetism, Terrestrial Magnetic Field and Polar Reversals Jack Oughton 

2. Definitions Dynamo - A system that uses electromagnetic induction to convert mechanical energy (motion) into a magnetic field Ferromagnetism is believed to be caused by magnetic fields generated by the electrons' spins in combination with a mechanism known as exchange coupling , which aligns all the spins in each magnetic domain. Curie temperature (Tc ) The temperature above which a ferromagnetic material loses its permanent magnetism. In minerals, lightning often flash-heats minerals above their Curie temperatures, effectively resetting the magnetic fields trapped in lava flows.