Traces of sun storms locked in tree rings could confirm ancient historical dates

Aug 17, 2016

By Tim Radford

Archaeologists believe they have identified a new way of putting accurate dates to great events of prehistory. Rare and spectacular storms on the sun appear to have left their mark in forests and fields around the planet over the past 5,000 years.

Michael Dee, of Oxford University’s research laboratory for archaeology and the history of art, thinks evidence of such solar storms could help put precise years to some of the great uncertainties of history: the construction of Egypt’s Great Pyramid of Giza, the collapse of the ancient Mayan civilisation in Central America, and perhaps even the arrival of the Vikings in the Americas.

Every tree maintains its own almanac in the form of annual growth rings. For decades dendrochronologists have been using tree-ring evidence and radiocarbon dating to build a timetable of events that confirm historical accounts, even those predating the first written chronicles.


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8 comments on “Traces of sun storms locked in tree rings could confirm ancient historical dates

  • @OP – link – The technique is imprecise, with an error range of 50-100 years, and also expensive. However, the discovery of unusually high levels of C-14 – up to 20 times the normal level – laid down in during especially violent solar storms may enable scientists to date material much more accurately. Every tree growing at the time of such a sun storm, anywhere in the world, would have preserved a record of it.

    In 2012, the Japanese scientist Fusa Miyake identified a dramatically raised level of C-14 in one set of growth rings that is known to date from 775AD. Since then, what the Oxford team call a second Miyake event – a consequence of a catastrophic extraterrestrial discharge of energy – has been identified from the year 994AD.

    Dee and his co-author Benjamin Pope propose a new science, astrochronology, to harness this solar storm evidence, in an article in the journal Proceedings of the Royal Society A . The technique could very precisely tie so-called “floating chronologies” of ancient Egypt , Mayan civilisation or the bronze age to fixed dates in the universal calendar.

    This is brilliant!
    The tree ring spikes in Carbon 14 are global affecting all trees, so wooden artefacts from all over the world can be dated, regardless of the historical local calendars.

    Also, once a high C14 tree ring is identified, the annual tree rings can be counted forward or back in any piece of wood, any historical wooden object, or any living tree.



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  • Amazing stuff! One of the most intractable problems in dendrochronology has been in comparing wood growth ring patterns from different climate areas. What might have a been a poor year for growth in one locality could have been a good year somewhere else hence generating a completely different ring pattern. If we could now find common markers that help unite the various unbroken dendrochronological chains from around the world we might be able to get an unbroken chain going back hundreds of thousands of years or even more.



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  • Arkrid Sandwich #2
    Aug 17, 2016 at 7:17 pm

    If we could now find common markers that help unite the various unbroken dendrochronological chains from around the world we might be able to get an unbroken chain going back hundreds of thousands of years or even more.

    Unfortunately in tree-ring studies, the reliability diminishes after tens of thousands of years, because of its relatively short half-life.

    One of C14’s applications in tracking global warming, is that in CO2 from fossil coal and oil deposits, the C14 content is effectively zero where as CO2 percentage from say burning forests, is measurable.

    http://hyperphysics.phy-astr.gsu.edu/hbase/nuclear/cardat.html
    Carbon-14 decays with a halflife of about 5730 years by the emission of an electron of energy 0.016 MeV. This changes the atomic number of the nucleus to 7, producing a nucleus of nitrogen-14. At equilibrium with the atmosphere, a gram of carbon shows an activity of about 15 decays per minute.

    The low activity of the carbon-14 limits age determinations to the order of 50,000 years by counting techniques. That can be extended to perhaps 100,000 years by accelerator techniques for counting the carbon-14 concentration.

    For dating more the more distant past other isotopes have to be used, but these are probably not to be found in tree rings.
    C14 is however invaluable for dating in archaeology but not in palaeontology.



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  • I don’t get it. I could see how you could use it to calibrate tree rings, but what provides the tie between tree rings, solar flares and historical events? Further, how do we know when prehistoric solar flares occurred?



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  • Roedy #6
    Aug 18, 2016 at 5:41 am

    I don’t get it. I could see how you could use it to calibrate tree rings,

    The intense radiation which creates C14 in the upper atmosphere, creates much more than the background levels in normal years. Consequently the tree ring for that year has an exceptionally high percentage of C14 to C12 in that year’s growth ring.

    but what provides the tie between tree rings, solar flares and historical events?

    The higher levels of C14 affect tree ring growth globally. therefore events across the whole world can be fixed at these dates where the wood is tested. The problem with dendrochronology is that it is very approximate and has an error bar of decades.

    Because the C14 peaks are global only odd samples need to be dated by independent methods (other isotopes in nearby materials or associated datable artefacts such a coins, pottery or inscriptions.)

    Having fixed the peak year tree rings in a sample, a normal count of other rings in the same pieces of wood, can calculate dates from each ring indicating each season’s annual growth.

    Further, how do we know when prehistoric solar flares occurred?

    In the examples given – it is from the observations of ancient astronomers, but if a large selection of wood samples was examined, the normal counting of tree rings matching irregular seasons patterns in wood grown in particular locations, would build up records into the distant past by joining up patterns from living trees and ancient wood. – known as “the bridging method”!

    http://www.learnnc.org/lp/editions/intrigue/1008
    An astronomer, Dr. Andrew E. Douglass, developed dendrochronology about 1913. Based at the University of Arizona in Tucson, Douglass wanted to know how sun spot activity affected climate, and his research soon led him to pioneering tree-ring analysis. Douglass was among the first to notice that trees in a geographic area develop the same growth-ring patterns because they experience the same climatic conditions. He reasoned if he could trace patterns far enough back in time, he could outline a history of regional climate and see if sun spots could be related.

    Douglass used a bridging method to create his chronology. First he studied recently cut trees whose dates he knew. This initial step was critical because by knowing the cut date, Douglass knew when each tree added its last growth ring. This, in turn, let him determine the year each tree started growing. The calculation was straightforward: count the dark rings inward and subtract that number from the year the tree was cut. As Douglass matched and recorded ring patterns from trees of different ages, he confirmed that their patterns overlapped during the years the trees simultaneously lived.

    After establishing this basic sequence, Douglass next studied wood from trees whose dates he did not know. He observed that the year a tree was chopped down could be determined by matching its ring pattern with the pattern of a tree whose cut year he knew. For example, say Douglass observed on his preliminary sequence that a drought occurred in 1900, appearing on trees as a very narrow growth ring. Experience told him this narrow ring would be in all the region’s trees, but at different positions on the stump because of their different ages. Faced with wood whose felling date he did not know, Douglass would search out the ring identifying the drought year and match it to his sequence. At that point, determining the year the tree was chopped down was, again, straightforward. For instance, if two growth rings exist above the drought year, the tree was cut in 1902. Douglass extended this bridging exercise by studying ring patterns visible in old wooden beams, some preserved in the pueblos (houses) of early Native Americans living in his study area. Ultimately, he charted a tree ring sequence to about AD 500.

    Dendrochronologists have since used Douglass’s technique to make master sequences for several parts of the country. Most reflect regional growth patterns for distinct species. Much of this work focused on regions in the arid Southwest where ancient pinyon pines still live or exist as beams in old houses. In some places there, master sequences extend as far back as 8,700 years.



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  • Steve Jones, who’s usually good for a laugh, has written an interesting slim volume entitled, The Serpent’s Promise – the Bible retold as science -, in which he offers plausible explanations for numerous ancient “revelations”.

    This discovery would seem to have the potential to be good fun in that regard too.

    I would have presumed that this particular component of dendrochronology would have been known about for a long time, so why have the findings only just been published?



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