The mysteries of Earth’s polar reversal are believed to be revealed by the rings of an ancient tree – one of the oldest ever found.
The tree, Agathis australis, better known by its Maori name Kauri, was discovered in New Zealand. It was uncovered at Northland's Ngāwhā about three months ago during excavations for a geothermal power plant expansion, reports stuff.nz.
The tree trunk – eight feet in diameter and 65 feet in length – was buried in about 8m of soil and was preserved like swamp kauri despite not actually being in a swamp.
Carbon dating revealed that it lived for 1500 years, between 41,00 and 42,500 years ago.
A team of international scientists believe its log could map out what to expect during a geometrical reversal – a change in the planet’s magnetic field – including its impact on climate change and solar radiation.
"There's nothing like this anywhere in the world," Alan Hogg from New Zealand's University of Waikato, told stuff.nz. "This Ngāwhā kauri is unique."
During its 1500-year lifespan, the tree experienced one of the Earth's geomagnetic excursions, meaning the north magnetic pole drifted down to the southern hemisphere and back up again.
“While knowledge of the geomagnetic excursion was not new, a tree that spanned the entire excursion timeframe had never been found,” Hogg said.
The scientist think that it would give a picture of the solar radiation in the Earth’s atmosphere during the excursion.
As the magnetic poles moved, the strength of Earth's geomagnetic field weakened, letting in more cosmic radiation, he said.
And the tree would show what to expect during another polar excursion or reversal – which scientists said was not a matter of if, but when.
"We will have increased cosmic radiation. It will take out satellites and it might take out other communication infrastructure," Hogg said.
Ngāwhā Generation – a subsidiary of Northland power wholesaler Top Energy – gave the kauri tree back to iwi on the agreement scientists could take samples for study.