What happens if the magnetic field is changing

The time intervals between reversals have fluctuated widely, but average about , years, with the last one taking place about , years ago. The magnetic field becomes jumbled, and multiple magnetic poles can emerge in unexpected places. Deep ocean sediment samples indicate glacial activity was stable. In fact, geologic and fossil records from previous reversals show nothing remarkable, such as doomsday events or major extinctions. During the last major excursion, called the Laschamps event, radiocarbon evidence shows that about 41, years ago, the magnetic field weakened significantly and the poles reversed, only to flip back again about years later.

Its magnitude is typically less than one to a few milliwatts per square meter. There is simply not enough energy aloft to have an influence on climate down where we live. Earth is surrounded by a system of magnetic fields, called the magnetosphere. The magnetosphere shields our home planet from harmful solar and cosmic particle radiation, but it can change shape in response to incoming space weather from the Sun. A constant outflow of solar material streams out from the Sun, depicted here in an artist's rendering.

A fossilized tree discovered in New Zealand has helped researchers date one of these magnetic flips to about 41, years ago, a time when Earth also saw megafauna extinctions, climatic changes and even a rise in cave art.

Related : The history of the world is written in tree rings. Scientists call this particular magnetic reversal the Laschamps excursion. They can date this event by studying the rock record. The Laschamps excursion lasted only a few hundred years, but scientists are interested in it because they think it might help them figure out how a magnetic reversal might have affected creatures living on Earth at the time.

But being able to link them to this event is the real trick. Some of these ancient coniferous trees are still living in New Zealand today and their antecedents have been around since the Jurassic period, millions of years ago, Gramling says. The particular trees in this peat bog date to about 50, years ago. A lot of giant old trunks, some of them several meters in diameter, are buried in these bogs and have been preserved there, Gramling says.

People dig them out for selfish purposes — to use them for tabletops or pillars, for example — but they're important to science because they contain a record of climatic events. What Lathrop is trying to do is re-create the dynamo that we believe exists inside the core of the Earth. We know that the core is becoming increasingly volatile. The North magnetic pole is absolutely running through the Northern Hemisphere at 55 kilometers a year to the northwest.

We also know that the dipole is weakening fairly dramatically. If you look at satellite imagery, you can see that part of the magnetic field has already reversed in the Southern Hemisphere. This is something called the South Atlantic Anomaly. Does that tell us that a reversal is at hand? Scientists simply do not have enough information to make that conclusion.

The consequences for life on Earth are potentially devastating. What if one of those bands of extra radiation hits a very heavily populated part of the planet? Then, of course, there are the effects on all the creatures on the planet, as well as the effects on our electromagnetic system, the electric grid, and all the things we consider part of modern civilization.

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