UOW Professor Richard ''Bert'' Roberts with a satellite image of the Toba volcanic caldera in northern Sumatra. Picture: KEN ROBERTSON
A University of Wollongong academic has been part of an international research team which has helped pinpoint the timing - give or take a few centuries - of the largest volcanic eruption on earth in the last two million years.
Professor Richard "Bert" Roberts, from the Centre for Archaeological Science, said this "super-eruption" took place some 73,880 years ago in northern Sumatra, leaving a 100-kilometre long, 30-kilometre wide and 500-metre deep crater - now Lake Toba - in its wake.
Prof Roberts said technological advances had enabled the research team to more accurately date the Toba eruption, which has important implications for the history of the planet.
"Knowing the exact date of this volcanic eruption allows us to more fully investigate its impact on the world's climate, plants and animals," he said.
"For instance, we now know that it happened at the same time as a period of dramatic climatic cooling of the earth - and while it may not have been the initial trigger for it, the eruption would have exacerbated it.
"The dating also tells us that the blast occurred at a time when early modern humans were spreading out of Africa and east across Asia, as stone tools have been discovered buried beneath Toba ash [at the archaeological site in Malaysia's Lenggong Valley].
"This fits in with recent revisions to the 'molecular clock' for human evolution."
Prof Roberts worked with team leader Dr Michael Storey, from Roskilde University in Denmark, on the study, which was published online this week in the Proceedings of the National Academy of Sciences of the USA.
He said the ten-fold improvement in precision on previous age estimates of the eruption had been made possible by the recovery of large crystals of sanidine (a volcanic mineral) in ash deposits in the Lenggong Valley.
"'Previously we only had fine-grain volcanic material recovered from the eruption, but last year a bore hole was put down into the valley and Michael recovered two-millimetre crystals," he said.
"The best way to date ash is a method called argon dating, which measures the amount of argon gas accumulated inside the crystals.
"The sanidine crystals had enough argon in them to allow us to carry out more accurate and precise dating using the latest advances in instrumentation."
The Toba explosion ejected more than seven trillion tonnes of volcanic material which spread as far west as the Arabian Sea. Gases even reached ice caps in Greenland and Antarctica.
"After the Mount Tambora eruption in Indonesia in 1815 the world's climate dropped by half a degree. There was no summer the following year and crops failed," Prof Roberts said.
"That eruption was 100 times smaller than Toba, yet it obviously had an effect on the world's climate.
"So you can only imagine what impact Toba must have had on Homo sapiens when it exploded. The legacy of this eruption might still be in our genes."