Sydney university conduct magnetic field study using ancient trees
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Around 42,000 years ago, Earth’s magnetic field was involved in a pole reversal. The event is known as the Laschamps Excursion, after the French town in which evidence was discovered. Evidence was found in rocks, which are a good record of the planet’s magnetic field.
As new rocks form, usually though lava flows or ocean sediment being dumped, they record the magnetic field at the time, which is what geologists used to date the last magnetic field reversal.
The Laschamps Excursion was only temporary, with the switch lasting for only a matter of centuries, but the results were devastating.
As the magnetic field switches, it becomes weaker and allows for more solar radiation to penetrate the atmosphere.
However, new research from a team of scientists from Australia found there was an increase in activity in the Sun at the same time as the Laschamps Excursion, which only exacerbated the situation.
The researchers wrote in The Conversation: “This last major geomagnetic reversal triggered a series of dramatic events that have far-reaching consequences for our planet.
“They read like the plot of a horror movie: the ozone layer was destroyed, electrical storms raged across the tropics, solar winds generated spectacular light shows (auroras), Arctic air poured across North America, ice sheets and glaciers surged and weather patterns shifted violently.
“During these events, life on earth was exposed to intense ultraviolet light, Neanderthals and giant animals known as megafauna went extinct, while modern humans sought protection in caves.”
The researchers made the discovery after analysing the rings of kauri trees in New Zealand which had been preserved in sediments for more than 40,000 years.
Tree rings show atmospheric changes over periods of time.
The researchers added: “Using the annual growth rings in the kauri trees, we have been able to create a detailed timescale of how Earth’s atmosphere changed over this time.
“The trees revealed a prolonged spike in atmospheric radiocarbon levels caused by the collapse of Earth’s magnetic field as the poles switched, providing a way of precisely linking widely geographically dispersed records.”
Professor Alan Cooper, who led the project, said: “The kauri trees are like the Rosetta Stone, helping us tie together records of environmental change in caves, ice cores, and peat bogs around the world.”
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Earth’s magnetic field not only protects our planet and its life from deadly solar radiation, but it keeps north at the top and south at the bottom of the planet’s poles.
The shield is created by the liquid iron outer core of our planet spinning around the solid inner core.
The dynamic action creates an invisible field which goes through the north and south of the planet and encircling it, which leads to the Earth’s North and South Poles.
Many species of animals, most notably birds, have a sense for the magnetic poles which allow them to successfully navigate the globe during periods of mass-migration, leading experts to fear that it could cause confusion.
The shield also keeps us protected from cancer-causing solar rays and humans have grown to rely on the magnetic field more and more as we increase our independence on things like satellites which we use for navigation, mobile phones and satellite TV – to name just a few examples.
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