MAGNETS AND MAGNETIC FIELDS
The theory of magnetic fields indicates that an object is magnetized when part or all of its atomic elements have their north and south poles aligned. Earth’s magnetic field is produced by the rotation and movement of the planet’s molten iron core. This produces a magnetic field that is relatively stable in direction.
Because of this stable magnetic field, early explorers could reliably use compasses built with lodestone, charged iron needles and other naturally magnetic materials. The Earth itself can be considered a bar magnet because of its two poles. Quite frequently, the magnetic field surrounding the Earth strongly magnetizes large ferromagnetic objects that lie aligned with the Earth’s poles for periods of time.
The directions of the Earth’s magnetic field may be changed by major geologic events over many thousands of years. There are many local magnetic anomalies having higher levels of magnetic attraction near the Earth’s surface. It is thought that these may be caused by iron or nickel deposits.