Iceland was not settled until around 870, so this particular forest was destroyed almost half a century before humans arrived.The unique tree ring results were then linked with those of co-authors Professors Christine Lane and Clive Oppenheimer, also from Cambridge’s Department of Geography.The so-called Drumbabót forest is the best-preserved prehistoric forest in Iceland, and had been buried by an eruption of the nearby Katla volcano, Iceland’s most active volcanic system.
By measuring the radiocarbon levels in one of the Drumbabót trees, Büntgen and his colleagues were able to pinpoint the year 775 in the tree rings, and measure outward to the bark to count the number of years to the Katla eruption, when the tree died.
The outermost tree ring had completely formed and a new one had not yet started, meaning that the eruption occurred after autumn 822 and before spring 823, before the next year’s growth had begun.
However, also among the rubble was a clay ink bottle, in almost the exact same condition as it was when discarded, which presented an opportunity to date this historical rubbish tip.
Trinity College presents an excellent opportunity for this kind of proxy dating, as its landscaping has remained largely unchanged for centuries and, being part of a well-surveyed city, can be traced back with the history of the city.
Take for example the grounds-men in Trinity College Dublin (home of this blog) who recently unwittingly revealed one of these recent pasts while prospecting for a lost water main under the college rugby pitch.
Just beneath the veneer of well-manicured grass were found numerous oyster shells (indicative of the well-heeled diet of Trinity’s historical elite) and broken masonry, from a seemingly unidentified period.
Lane and Oppenheimer used independent lines of ash (tephra) and ice core evidence to detect fingerprints of the Katla eruption.
In addition to the scientific results, the team also involved historians who analysed written documentary evidence from Europe and Asia, and found that there was a severe cold spell consistent with the timing of the reconstructed Katla eruption.
While was its first registrar, now it is moved to Dot TK Domain Registry.