Earth’s Magnetic Pole Reversal – Don’t “Flip Out”!

by Tammy Plotner on December 5, 2011

Schematic illustration of Earth's magnetic field. Credit/Copyright: Peter Reid

Have you heard or read stories about how Earth will some day reverse its magnetic poles? If you have, then chances are very good you’ve also heard this perfectly normal function of our planet could spell disaster. Before you buy into another “end of the world as we know it” scenario, let’s take a look at the facts.

For the record, we know that Earth’s magnetic field has changed its polarity more than once in its lifetime. For example, if you could step back in time some 800,000 years ago with a compass in your hand, you’d see the needle pointed to south – instead of north. Why? Because a compass works on magnetic fields, its needle directs you to the magnetic pole, measured as either positive or negative. The markings on the modern compass dial would be incorrect if the polarity of Earth’s magnetic fields were reversed! Like a witch hunt, many would-be prophets say natural occurrences like this might signal doom… But could their theories be correct? Unfortunately for hyperbole, the geologic and fossil records from past reversals show the answer is “No.” We’ll still be around.

Just like the Sun reversing its magnetic poles, Earthly switches are just a part of our planet’s schedule. During about the last 20 million years of our formation, Earth has settled into a pattern of switching magnetic poles about every 200,000 to 300,000 years… with a period of twice that long since our last reversal. And, it’s not a thing that happens rapidly. Magnetic pole reversal takes up to several hundred thousands of years to complete. The fields blend together and magnetic poles pop up at odd latitudes as it happens. It’s not that scary! Scientists say that Earth has reversed its magnetic field hundreds of times over the last three billion years and have sped up slightly with time.

How do we know about the impacts of magnetic pole reversal? We take a look at the deep evidence – sediment cores taken from the ocean floor. These samples are perfect fossil records which show us what direction the magnetic field was pointed in as the underwater lava emerged. These ancient flows were magnetized in the field’s direction at the time of their creation and exist on either side of the Mid-Atlantic Rift where the North American and European continental plates are moving away from each other.

“The last time that Earth’s poles flipped in a major reversal was about 780,000 years ago, in what scientists call the Brunhes-Matuyama reversal. The fossil record shows no drastic changes in plant or animal life.” says NASA’s Patrick Lynch. ” Deep ocean sediment cores from this period also indicate no changes in glacial activity, based on the amount of oxygen isotopes in the cores. This is also proof that a polarity reversal would not affect the rotation axis of Earth, as the planet’s rotation axis tilt has a significant effect on climate and glaciation and any change would be evident in the glacial record.”

A schematic diagram of Earth's interior and the movement of magnetic north from 1900 to 1996. The outer core is the source of the geomagnetic field. Graphic Credit: Dixon Rohr

Unlike a hard-wired magnet, Earth’s polarity isn’t constant – it moves around a bit. The reason we have a magnetic field is our solid iron core surrounding by hot, fluid metal. According to computer modeling, this flow creates electric currents which spawn the magnetic fields. While it’s not possible at this point in time to measure the outer core of our planet directly, we can guess at its movement by the changes in the magnetic field. One such change has occurred for almost 200 years now… Our northern pole has been shifting even more northward. Since it was first located, the pole has shifted its place by more than 600 miles (1,100 km)! What’s more, it’s speeding up. It would seem that it’s moving almost 40 miles per year now, instead of the 10 miles per year as recorded in the early 20th century.

Don’t be fooled by those saying a magnetic pole reversal would leave us temporarily without a magnetic field, either. This is simply isn’t going to happen and we’re not going to be exposed to harmful solar activity. While our magnetic field goes through weaker and stronger phases, there is simply no evidence to be found anywhere that it has ever disappeared completely. Even if it were weakened, our atmosphere would protect us against incoming particles and we’d have more auroral displays at lower latitudes!

So, go ahead… Sleep at night. Earthly magnetic pole reversal is a normal function of our planet and when it does happen its effects will be spread out over hundreds of thousands of years – not flipped like a pancake.

Original Story Source: NASA Earth News. For Further Reading: Earth’s Inconstant Magnetic Field..

About 

Tammy is a professional astronomy author, President Emeritus of Warren Rupp Observatory and retired Astronomical League Executive Secretary. She’s received a vast number of astronomy achievement and observing awards, including the Great Lakes Astronomy Achievement Award, RG Wright Service Award and the first woman astronomer to achieve Comet Hunter's Gold Status.

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