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Ancient Northland swamp kauri solves 42,000 year old mystery
21 Feb, 2021 05:00 PM
7 minutes to read
Some of this giant ancient swamp kauri tree uncovered at Ngāwhā has been used by researchers to confirm the date when the Earth reversed its magnetic poles. Photo / Peter de Graaf
Northern Advocate
Ancient swamp kauri from Northland has been used to confirm a temporary breakdown of Earth s magnetic field 42,000 years ago sparked major climate shifts leading to global environmental change and mass extinctions.
A new international study using ancient swamp kauri from Ngāwhā shows this dramatic turning point in Earth s history was triggered by a reversal of Earth s magnetic poles and changing solar winds.
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The importance of preserving kauri has perhaps never been clearer.
Scientists looking at ancient kauri trees in Northland say they ve come across evidence within them that could rewrite human history. It s the most surprising and important discovery I ve ever been involved in, said Professor Alan Cooper of the South Australian Museum, who co-led the new research, published Friday in journal
So what exactly did they find? Evidence that about 42,000 years ago the Earth s magnetic pole went haywire, perhaps wiping out the Neanderthals, but sending Homo sapiens into the safety of caves and inspiring art that we re still finding today.
While the approximate date of the pole shift was already known, examination of the kauri has allowed scientists to precisely date the timing and environmental impacts of the last magnetic pole switch , according to Chris Turney, professor at the University of New South Wales.
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But according to the team s findings, the most dramatic part was the lead-up to the reversal, when the poles were migrating across the Earth. Earth s magnetic field dropped to only 0 to 6 per cent strength during the Adams Event, said Professor Turney. We essentially had no magnetic field at all – our cosmic radiation shield was totally gone.
During the magnetic field breakdown, the Sun experienced several grand solar minima (GSM) – long-term periods of quiet solar activity.
Even though a GSM means less activity on the Sun s surface, the weakening of its magnetic field can mean more space weather – like solar flares and galactic cosmic rays – could head Earth s way.