Earth’s Last Magnetic Field Reversal Took Far Longer Than Thought

Computer simulation of the Earth’s field in a period of normal polarity between reversals. The lines represent magnetic field lines, blue when the field points towards the center and yellow when away. The rotation axis of the Earth is centered and vertical. The dense clusters of lines are within the Earth’s core. (Dr. Gary A. Glatzmaier / Los Alamos National Laboratory / U.S. Department of Energy / NASA)

(CN) – The reversal of Earth’s magnetic field, which took place more than half a million years ago, took much longer than previously believed, according to new research.

Our planet’s magnetic field allows us to create navigation systems and makes technology like GPS reliable. The field is created by the outer core of liquid iron as it spins around the inner core. It slowly shifts, and the North and South poles eventually reverse.

New geological research into lava flows around the world, published in the journal Science Advances on Wednesday, gives scientists new insights into the phenomenon.

There is a dispute over the length of the magnetic field reversals and how often they occur, although many have taken place over millions of years. Some scientists believe we are in the beginning stages of a reversal, which could have serious implications for our electronics and navigation systems.

Rock forms, such as lava flows from volcanoes or ocean floor sediments, provide scientists with information about the field reversals.

“Lava flows are ideal recorders of the magnetic field,” said geologist Brad Singer from the University of Wisconsin-Madison. “They have a lot of iron-bearing minerals, and when they cool, they lock in the direction of the field.”

Mount Etna volcano spews lava during an eruption. (Orietta Scardino/ANSA via AP)

He added: “But it’s a spotty record. No volcanoes are erupting continuously. So we’re relying on careful field work to identify the right records.”

Singer – the lead author of the study – and his team attempted to recreate the magnetic field over a 70,000-year span using seven different lava flow sequences.

The team found that the last reversal took less than 4,000 years which, geologically speaking, is a very short amount of time. Before that, Earth experienced an 18,000-year period of instability, which is twice as long as other research has recently suggested.

The magnetic field has gradually been weakening in the time that people have been recording it – at a rate of about 5% every 100 years.

This does not mean, however, that a reversal is going to happen soon. The study suggests that humans will have generations to adjust to a period of instability.

“I’ve been working on this problem for 25 years,” Singer said. “And now we have a richer record and better-dated record of this last reversal than ever before.”

Singer conducted his research with scientists from the University of California, Santa Cruz, and Japan’s Kumamoto University.

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