Thursday, October 3, 2019

Ancient Tree Reveals Geomagnetic Changes

(Photo credit: A. J. Timothy Jull)

Scientists are trying to gain a better understanding of the global geomagnetic field during extreme changes in the field such as reversals and shorter term excursions. To understand shifts in the geomagnetic field, a huge amount of data has to be gathered and compared. The data is gathered from lava flows, old ice masses, and magnetized minerals inside solidified igneous rock.

Another source of data comes from very old tree rings. Tree rings reveal climate changes due to excursions.

Research suggests that Earth was blasted with a period of intense solar activity about 7000 years ago. Traces of the event can be seen in the carbon signature of some very old tree rings.

Evidence of the solar event was found while looking at the amount of the carbon-14 isotope in the rings of an ancient bristlecone pine tree from California, pictured above.

Kauri tree unearthed during the expansion of the Ngāwhā geothermal power plant.
 (Photo credit: Nelson Parker)

Recently, an ancient tree was discovered in New Zealand that contains a record of a reversal of Earth's magnetic field. The tree species is called Agathis australis, known by its Māori name Kauri. It was discovered buried under 26 feet of soil during excavation work for the expansion of a geothermal power plant.

The tree measures eight feet in diameter and 65 feet in length. Carbon dating revealed it lived for 1,500 years, between 41,000 and 42,500 years ago. Read more about this fascinating discovery here.

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