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What creates and what reverses geomagnetism?

What created magnetism and what stimulates a change in the earth’s polarity?
Laura Price from Gloucestershire (Age 35-44)

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One Response

  1. At the centre of our Earth is an extremely hot, solid iron ball. Surrounding this inner core of iron is a very deep, seething layer of liquid iron known as the outer core. The Earth’s magnetic field comes from this ocean of iron, which is an electrically conducting fluid in constant motion. The flow of the fluid inside the Earth’s liquid outer core is turbulent, teeming with whorls and eddies. These complex motions generate the Earth’s magnetism through a process called the dynamo effect. Sometimes the magnetic field completely flips with the result that the north and the south poles swap places. Scientists cannot predict such reversals but they are presently constructing computer simulations using geodynamo models. Reversals, as recorded in the magnetism of ancient rocks, come at irregular intervals averaging about 300,000 years; the last one was 780,000 years ago.

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