The Earth's molten core has electric currents flowing through it.
As the earth rotates, these electric currents produce a magnetic field that extends outward into space.
The Earth's magnetic north pole can change in orientation (from north to south and south to north), and has many times over the millions of years that this planet has existed.
The term that refers to changes in the Earth's magnetic field in the past is paleomagnetism.
Several dating methods exist, depending on different criteria and techniques, and some very well known examples of disciplines using such techniques are, for example, history, archaeology, geology, paleontology, astronomy and even forensic science, since in the latter it is sometimes necessary to investigate the moment in the past in which the death of a cadaver occurred.
Thus, 1587 is the post quem dating of Shakespeare's play Henry V.The ancient orientation and intensity of the earth's magnetic field is preserved by the magnetization of iron oxides in rocks and sediments and archaeological materials (archaeomagnetism).Ancient direction and intensity of the earth's magnetic field may be preserved in three ways: a) thermoremanet magnetism (T. M.) works through the alignment of the magnetic domains within iron minerals when heated to above the Curie point and subsequently cooling, b) detrital remanent magnetism works through the alignment of clay particles sinking down slowly through still lake or deep ocean water.This process, in which the rotation of a planet with an iron core produces a magnetic field, is called a dynamo effect.The Earth's magnetic core is generally inclined at an 11 degree angle from the Earth's axis of rotation.