-- Arrival of modern humans in Southeast Asia considered - 8/01/17
-- Aftermath of super eruption shows Toba magma system's great size - 5/16/17
of modern humans in Southeast Asia considered (See note 1)
Humans may have exited out of Africa and arrived in Southeast Asia 20,000 years earlier than previously thought, a new study involving University of Queensland researchers suggests.
Findings from the Macquarie University-led study also suggest humans could have potentially made the crossing to Australia even earlier than the accepted 60,000 to 65,000 years ago.
Dr Gilbert Price of UQ School of Earth and Environmental Sciences said the dating of a cave site in West Sumatra, called Lida Ajer, provided first evidence for rainforest use of modern humans.
“Rainforests aren’t the easiest place to make a living, especially for a savannah-adapted primate, so it suggests that these people were ahead of the curve in terms of intelligence, planning and technological adaptation,” Dr Price said.
He said the study stood on the shoulders of brilliant Dutch paleo-anthropologist Eugene Dubois, famed for his discovery of ‘Java Man’.
“He visited a series of caves in Sumatra in the late 1800s, and in one in particular, recovered some human teeth, which is quite interesting in itself, but no one had spent much time trying to determine their significance,” Dr Price said.
“Fast forward over 100 years later, both the team of lead author Dr Kira Westaway of Macquarie University and my crew (separately) were lucky enough to re-discover and visit the caves.
“It was quite an adventure. We ended up sharing notes and the collaboration was born.”
As a result of thorough documentation of the cave, reanalysis of the specimens, and a new dating program, it was confirmed the teeth were modern humans, Homo sapiens, but dated to as old as 73,000 years ago.
A barrage of dating techniques were applied to the sediment around the fossils, to overlying and underlying rock deposits in the cave and to associated mammal teeth, indicating that the deposit and fossils were laid down between 63,000 to 73,000 years ago.
“This cave has been shrouded in doubt since it was first excavated” Dr Westaway said.
“We employed a range of dating techniques from different institutions to establish a robust chronology that would, after 120 years, finally put an end to the uncertainty associated with the age and significance of these teeth.”
Advanced equipment at UQ’s Centre for Geoanalytical Mass Spectrometry, a hub backed by researchers from Queensland’s major research institutions, was used in the analysis.
“We were lucky to have some of the best dating facilities in the world at our disposal, including the same pieces of equipment at UQ that had earlier dated the famous ‘Hobbit’ fossils of Southeast Asia,” Dr Price said.
Dr Westaway said the hardest part was trying to find the site again, with only a sketch of the cave and a rough map from a copy of Dubois’s original field notebook to guide them.
Southeast Asia is a key region in the path of human dispersal from Africa round to Australia, as all hominines would have had to pass through this region en route to Australia.
UNIVERSITY OF QUEENSLAND
of super eruption shows Toba magma system's great size (see note 2)
Oregon State University May 16, 2017
The rare but spectacular eruptions of super volcanoes can cause massive destruction and affect climate patterns on a global scale for decades -- and a new study has found that these sites also may experience ongoing, albeit smaller eruptions for tens of thousands of years after.
In fact, Oregon State University researchers were able to link recent eruptions at Mt. Sinabung in northern Sumatra to the last eruption on Earth of a super volcano 74,000 years ago at the Toba Caldera some 25 miles away.
The findings are being reported this week in the journal Nature Communications.
"The recovery from a super volcanic eruption is a long process, as the volcano and the magmata system try to re-establish equilibrium -- like a body of water that has been disrupted by a rock being dropped into it," said Adonara Mucek, an Oregon State doctoral candidate and lead author on the study.
"At Toba, it appears that the eruptions continued for at least 15,000 to 20,000 years after the super eruption and the structural adjustment continued at least until a few centuries ago -- and probably is continuing today. It is the magmata equivalent to aftershocks following an earthquake."
This is the first time that scientists have been able to pinpoint what happens following the eruption of a super volcano. To qualify as a super volcano, the eruption must reach at least magnitude 8 on the Volcano Explosivity Index, which means the measured deposits for that eruption are greater than 1,000 cubic kilometers, or 240 cubic miles.
When Toba erupted, it emitted a volume of magma 28,000 times greater than that of the 1980 eruption of Mount St. Helens in Washington state. It was so massive, it is thought to have created a volcanic winter on Earth lasting years, and possibly triggering a bottleneck in human evolution.
Other well-known super volcano sites include Yellowstone Park in the United States, Taupo Caldera in New Zealand, and Campi Flegrei in Italy.
"Super volcanoes have lifetimes of millions of years during which there can be several super eruptions," said Shanaka "Shan" de Silva, an Oregon State University volcanologist and co-author on the study. "Between those eruptions, they don't die. Scientists have long suspected that eruptions continue after the initial eruption, but this is the first time we've been able to put accurate ages with those eruptions."
Previous argon dating studies had provided rough ages of eruptions at Toba, but those eruption dates had too much range of error, the researchers say. In their study, the OSU researchers and their colleagues from Australia, Germany, the United States and Indonesia were able to decipher the most recent volcanic history of Toba by measuring the amount of helium remaining in zircon crystals in erupted pumice and lava.
The helium remaining in the crystals is a remnant of the decaying process of uranium, which has a well-understood radioactive decay path and half-life.
"Toba is at least 1.3 million years old, its super eruption took place about 74,000 years ago, and it had at least six definitive eruptions after that -- and probably several more," Mucek said. "The last eruption we have detected occurred about 56,000 years ago, but there are other eruptions that remain to be studied."
The researchers also managed to estimate the history of structural adjustment at Toba using carbon-14 dating of lake sediment that has been uplifted up to 600 meters above the lake in which they formed. These data show that structural adjustment continued from at least 30,000 years ago until 2,000 years ago -- and may be continuing today.
The study also found that the magma in Toba's system has an identical chemical fingerprint and zircon crystallization history to Mt. Sinabung, which is currently erupting and is distinct from other volcanoes in Sumatra. This suggests that the Toba system may be larger and more widespread than previously thought, de Silva noted.
"Our data suggest that the recent and ongoing eruptions of Mt. Sinabung are part of the Toba system's recovery process from the super eruption," he said.
The discovery of the connection does not suggest that the Toba Caldera is in danger of erupting on a catastrophic scale any time soon, the researchers emphasized. "This is probably 'business as usual' for a recovering super volcano," de Silva said. It does emphasize the importance of having more sophisticated and frequent monitoring of the site to measure the uplift of the ground and image the magma system, the researchers note.
"The hazards from a super volcano don't stop after the initial eruption," de Silva said. "They change to more local and regional hazards from eruptions, earthquakes, landslides and tsunamis that may continue regularly for several tens of thousands of years.
"Toba remains alive and active today."
As large as the Toba eruption was, the reservoir of magma below the caldera is much, much greater, the researchers say. Studies at other calderas around Earth, such as Yellowstone, have estimated that there is between 10 and 50 times as much magma than is erupted during a super eruption.
Materials provided by Oregon State University. Note: Content may be edited for style and length.
Adonara E. Mucek, Martin Danišík, Shanaka L. de Silva, Axel K. Schmitt, Indyo Pratomo, Matthew A. Coble. Post-super eruption recovery at Toba Caldera. Nature Communications, 2017; 8: 15248 DOI: 10.1038/ncomms15248
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Oregon State University. "Aftermath of super eruption shows Toba magma system's great size." ScienceDaily. ScienceDaily, 16 May 2017. https://www.sciencedaily.com/releases/2017/05/170516143417.htm
1. This is within the time that Toba blew itself apart, causing tremendous damage to the Indonesian area but also to the rest of the world when the ash began circling the globe. When food supplies dwindled it would have been time to move on or set down and die, why not then build your rafts and hope for the best.
2. This article speaks of the destruction the Toba eruption caused. It is reasonable to presume that the people that had reached the area years, perhaps millennia before was devastated by this super eruption. The only possible chance of survival was to try and reach Australia. They probably knew of the presents of land there by the occasional smoke observed from huge fires, such as still occur today.