RV: "Possibly more devastating than previously thought"
Fuente: Max-Planck-Gesellschaft - Forschung Expuesto el: jueves, 20 de junio de 2013 10:00 Autor: Max-Planck-Gesellschaft Asunto: "Possibly more devastating than previously thought"
"Possibly more devastating than previously thought"
Leipzig researchers have published new data on volcanic ash, known as the “Campanian Ignimbrite”, which covered wide parts of Europe
June 20, 2013
About 40,000 years ago Europe suffered a major volcanic eruption in the Phlegrean Fields west of Naples. Deposits known as "Campanian Ignimbrite" are still present in the region and bear witness to the event. The ash that was flung into the upper atmosphere from the CI eruption was distributed far across Eastern Europe. Computer models had predicted the ash layers in Eastern Europe to be between five and ten centimetres thick. New data from Urluia, Romania, however, demonstrates that CI ash deposits in the Lower Danube steppe are up to ten times thicker than previously thought. The eruption of the super volcano, which must have been substantially more explosive than previously modelled, impacted human evolution at a critical time - corresponding with the arrival into Europe of modern humans, and the demise of Neanderthals.
The most explosive volcanic eruption in Europe in the last 200,000 years took place in the Phlegrean Fields near Naples, Italy, about 40,000 years ago. This eruption produced "Campanian Ignimbrite", a mix of hot gas, volcanic ash and magma. The event coincided with the onset of a severely cold climatic phase. The volcanic winter likely induced by the super-eruption, combined with this short-lived, extreme “ice age”, may have increased the severity of the climate across Europe and possibly globally.
How explosive the super-eruption was has been modelled based on data from the thickness of ash deposits and their extent, as well as the chemistry and particle size of the volcanic products. CI ash has been found as far away as the Russian Plain, Eastern Mediterranean and northern Africa. There exist a number of ash sites from Italy and the eastern Mediterranean which provide input to the models of the super-eruption.
Up until now, however, there were no data points spanning the 1500 kilometres between sites in the Balkans and those on the Russian Plain. “During our survey for new archaeological sites in the lower Danube region, we discovered an unexpectedly thick ash deposit in the southeastern Romanian loess steppe. This deposit was up to 50-100 centimetres thick, which is substantially more than the predicted 5-10 cm based on the models”, says Kathryn Fitzsimmons of the Max Planck Institute for Evolutionary Anthropology. “Although we do not remodel the volcanic event, we hypothesise from our new observations that the eruption was substantially more explosive than previously estimated”.
The researchers confirmed that the ash deposit originated from the CI eruption in Italy using geochemical analyses of the major oxide concentrations. They used luminescence dating techniques – which measure when sediments were last exposed to sunlight – on the surrounding loess sediments to check that the timing of the ash deposition matches the known age of the eruption of about 39,000 years. A number of sediment features indicate that the tephra was deposited rapidly. At the contact between the tephra and underlying loess, imprints of vegetation are visible, along with possible traces of borings made by invertebrates. “The evidence from our study in Romania indicates rapid, thick deposition of relatively coarse-grained, far-travelled tephra from the CI super-eruption, more than 1200 kilometres from its source”, says Fitzsimmons.
What was the potential impact of rapid, thick deposition of ash on hominin populations in Eastern Europe, climate, and ecosystems? Measurements from this study reveal colder conditions immediately following the ash deposition. Chemical reactions between acidic volcanic gases, and atmospheric and soil moisture, produce acid rain and soil acidification in ashfall zones, contamination of freshwater systems, and fluoride poisoning of herbivores ingesting contaminated vegetation. This in turn impacts humans who eat the poisoned plants and animals, drink the water, and may also suffer from fluoride poisoning and associated bone deformation. In addition, volcanic ash can cause a variety of respiratory problems which can prove fatal.
Since the researchers have now identified widespread, thick CI ash deposits in southeast Romania, they will intensify their search for new archaeological sites, targeting the ash zones, which might yield direct insights into the impacts of the CI super-eruption on hominin populations at the gates to Europe. “Our discovery not only highlights the need to reassess models for the magnitude of the eruption and its role in climatic change, but also suggests that it may have substantially influenced hominin populations and their ability to survive in a region strategic for human migration into Europe”, says Fitzsimmons.
This study forms part of an international research project, the Lower Danube Survey for Palaeolithic sites (http://lodans.wordpress.com/about/), which brings together an interdisciplinary team of researchers from the Max Planck Institute for Evolutionary Anthropology, MONREPOS Archaeological Research Centre and Museum for Human Behavioural Evolution (RGZM), University of Bayreuth, and the Institutes for Archaeology and Speleology of the Romanian Academy of Sciences, in collaboration with researchers from the the Institute of Speleology of the Romanian Academy of Sciences and the Babes-Bolyai University, Cluj-Napoca, Romania.