An international group of researchers determined the date of a major volcanic eruption in Iceland. When it happened, there was not a single permanent settlement on the island, but large forests grew. Remains of ancient trees and told scientists about the events of the past.
The team, which included volcanoes, climatologists, geographers and historians, used a combination of scientific and historical data. The results of the study are published in the journal Geology.
Just as fossils can be used to understand the evolution and evolution of life on Earth, different types of environmental evidence can help to understand what the climate was in the past and why. “Prints of the past”, contained in tree rings and ice core, allow scientists to evaluate the former climatic conditions and expand our understanding of the interaction of people and the environment hundreds and thousands of years ago.
“In our work we are trying to restore the former variability of temperature and precipitation on the basis of tree rings, determining, for example, when it was cold and wet or warm and dry,” explained the lead author of the study, Professor Ulf Büntgen from the Geographical Department of Cambridge University.
“We are also interested in establishing key factors in climate dynamics and their possible links with changes in the history of mankind.”
Currently, Iceland is mostly forested. However, before the arrival of the first permanent residents at the end of the ninth century, its territory probably covered vast forests. Early settlers cut down trees to create a society based on agriculture. After human intervention, they have never recovered.
In 2003, during the spring flood on the river Tver, hundreds of birch trees emerged to the surface, which for centuries were buried under layers of volcanic sediment. The so-called forest of Drumbabot is the most preserved prehistoric forest in Iceland. He was buried by the eruption of the nearby volcano Katla, the island’s most active volcanic system.
Volcanic eruptions often cause a sharp cooling. To get a complete picture of climate change, you need to know the exact date of the eruption. In the new study, scientists used trees exposed by the flood of 2003 to determine when this particular eruption occurred.
Earlier the team confirmed that in 775 n. E. A large solar flare caused a splash in the level of radiocarbon in the Earth’s atmosphere, which was deposited in the trees that grew at that time. By measuring radiocarbon levels in one of the Drumbabota trees, Buntgen and his colleagues were able to isolate in the tree rings year 775 and measured the thickness to the outer crust to calculate the number of years before the eruption of Cutla when the tree was killed.
The outermost arboreal ring was fully formed, and the new one had not yet begun to appear. This means that the eruption occurred after the autumn of 822 and until the spring of 823, when the next ring was to begin to grow. In Iceland until 870 there were no permanent settlements, that is, the forest was killed almost half a century before the arrival of people.
The findings were compared with the results of Professors Christine Lane and Clive Oppenheimer, who used traces of ash (tephra) and evidence from the icy core to detect the “prints” of Catl’s eruption. The work was also attended by historians who analyzed written documentary evidence from Europe and Asia and found a period of severe cooling, according to the dates corresponding to the date of the eruption of Cutla, established on tree rings.