Discovery of volcanic ash at Pinnacle Point
About 74,000 years ago, a colossal volcano in Sumatra named Toba blew its top in the largest eruption to occur anywhere on Earth in the past 2 million years. Gas and ash spewed into the atmosphere and spread around the world within weeks, and some scientists think they triggered a global âvolcanic winterâ that may have lasted decades, leading to massive die-offs and the near-extinction of the human species. But others have suggested that the eruptionâs effects were less dramatic.
Now, subtle traces of volcanic ash at Pinnacle Point, a famous archaeological site on the southern coast of South Africa, suggest that at least some groups of early humans survived, and even thrived, in the eruptionâs aftermath. The discovery also offers archaeologists an astonishingly precise time marker for dating sites around the globe.
When Toba erupted, modern humans had already traveled out of Africa to at least the Middle East and perhaps beyond. Some researchers have proposed that Tobaâs eruption was big enough to cause a reverse greenhouse effect that cooled Earth for decades, leading to ecological disaster and widespread food shortages that only a few small communities were able to survive. (Volcanoes spew sulfur dioxide into the atmosphere, which can form aerosols that reflect the sunâs rays.) But the theory is hotly debated. Sediments from Lake Malawi, in eastern Africa, for example, donât show evidence for a dramatic change in plant life around the time of the eruption.Â Â
Archaeologists wanted to see whether they could find evidence for effects of the volcano at Pinnacle Point, a series of caves where archaeologists have uncovered a rich trove of bones, tools, and weapons left by Stone Age humans, some dating from nearly 200,000 years ago. They also studied Vleesbaai, an open-air site 9 kilometers away where researchers have found more Stone Age tools and animal bones.
The scientists took samples from every centimeter of sediment in a 1.5-meter vertical section of the Vleesbaai dig and also analyzed samples from key layers at Pinnacle Point. At both sites, they found a sparse sprinkling of cryptotephra, microscopic particles of glassy volcanic rock. The chemical signatures of these fragments matched Toba ash found in Malaysia and Lake Malawi. The ash layer marks the same dateâwithin a monthâacross the entire globe. Other dating techniques have about a 10% error rate, so a deposit dated as 74,000 years old could be anywhere between 66,000 and 81,000 years. Thus, the work offers a new way to correlate far-flung sites very precisely.
At Pinnacle Point, artifacts found just below and directly above the traces of ash show no gap in human use of the site, Marean and his colleagues report today in Nature. In fact, they say, the traces of human occupation intensify shortly after the volcanoâs eruption, suggesting that humans living there did just fine, Marean says. The Pinnacle Point people are known to have eaten shellfish and other marine resources, and he speculates that the ocean may have been buffered from the volcanoâs effect. âHunter-gatherer economies are really resilient,â Marean says. âThe impact on them is probably a lot lessâ than on flora and fauna.
But archaeologist Stanley Ambrose of the University of Illinois in Urbana, who proposed the idea that Tobaâs eruption wiped out most early humans, isnât convinced. Mareanâs team found sandy layers just above the ash traces, which Ambrose says are indeed a sign of dramatic environmental change and a decrease in human occupation. Marean counters that those layers were part of a series of sand dunes that formed in a matter of days or weeks after the eruption and include human artifacts. âSo no evidence for abandonment,â he says. Looking for volcanic traces at other sites could help settle the debate, he says.
Other researchers are impressed with the methodâs potential, in part because they were able to isolate rare particles of cryptotephra, down to two particles per gram of sediment. âItâs a beautiful marker,â says Michael Petraglia, an archaeologist at the Max Planck Institute for the Science of Human History in Jena, Germany. Itâs especially impressive that the team was able to find ash traces 9000 kilometers from the volcano, he says. He and his colleagues hope to use similar techniques at sites in East Africa and Arabia, he says. âWhen you find it, itâs fantastic.â
The two closest super volcanoes to the UAE are Lake Toba in Indonesia and The Campi Flegrei in Italy. If one of these erupted in a super volcano manner, do you think modern day humans are equipped to survive? State your opinion on this, and write what we as the population of the UAE may have to live through in order to survive.Â
- Effect on drinking water
- Effect on food supply
- Effect on temperature
- Effect on weather
- Effect on transport
- Effect on global climate
- Effect on population size and distribution