Earth has magnetic fields {magnetic field, Earth} {Earth magnetic field}, because thermal convection from iron-solidification latent heat and escape of inner-core iron oxide and iron sulfide causes liquid-iron outer-core spin {geodynamo}. Magnetic-field strength is 10,000 gauss at Earth surface. Magnetic field is decreasing. Magnetic field reverses polarity randomly, approximately every 250,000 years. Earth magnetic field has had same polarity for last 780,000 years.
Physical Sciences>Earth Science>Planet>Magnetism
5-Earth Science-Planet-Magnetism
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Date Modified: 2022.0224