A new study provides “incontrovertible evidence” that the volcanic super-eruption of Toba on the island of Sumatra about 73,000 years ago deforested much of central India, some 3,000 miles from the epicenter, researchers report.
The volcano ejected an estimated 800 cubic kilometers of ash into the atmosphere, leaving a crater (now the world’s largest volcanic lake) that is 100 kilometers long and 35 kilometers wide. Ash from the event has been found in India, the Indian Ocean, the Bay of Bengal and the South China Sea.
The bright ash reflected sunlight off the landscape, and volcanic sulfur aerosols impeded solar radiation for six years, initiating an “Instant Ice Age” that — according to evidence in ice cores taken in Greenland — lasted about 1,800 years.
During this instant ice age, temperatures dropped by as much as 16 degrees centigrade (28 degrees Fahrenheit), said University of Illinois anthropology professor Stanley Ambrose, a principal investigator on the new study with professor Martin A.J. Williams, of the University of Adelaide. Williams, who discovered a layer of Toba ash in central India in 1980, led the research.
The climactic effects of Toba have been a source of controversy for years, as is its impact on human populations.
In 1998, Ambrose proposed in the Journal of Human Evolution that the effects of the Toba eruption and the Ice Age that followed could explain the apparent bottleneck in human populations that geneticists believe occurred between 50,000 and 100,000 years ago. The lack of genetic diversity among humans alive today suggests that during this time period humans came very close to becoming extinct.
To address the limited evidence of the terrestrial effects of Toba, Ambrose and his colleagues pursued two lines of research: They analyzed pollen from a marine core in the Bay of Bengal that included a layer of ash from the Toba eruption, and they looked at carbon isotope ratios in fossil soil carbonates taken from directly above and below the Toba ash in three locations in central India.
Carbon isotopes reflect the type of vegetation that existed at a given locale and time. Heavily forested regions leave carbon isotope fingerprints that are distinct from those of grasses or grassy woodlands.
Both lines of evidence revealed a distinct change in the type of vegetation in India immediately after the Toba eruption, the researchers report. The pollen analysis indicated a shift to a “more open vegetation cover and reduced representation of ferns, particularly in the first 5 to 7 centimeters above the Toba ash,” they wrote in the journal Palaeogeography, Palaeoclimatology, Palaeoecology. The change in vegetation and the loss of ferns, which grow best in humid conditions, they wrote, “would suggest significantly drier conditions in this region for at least one thousand years after the Toba eruption.”
The dryness probably also indicates a drop in temperature, Ambrose said, “because when you turn down the temperature you also turn down the rainfall.”
The carbon isotope analysis showed that forests covered central India when the eruption occurred, but wooded to open grassland predominated for at least 1,000 years after the eruption.
“This is unambiguous evidence that Toba caused deforestation in the tropics for a long time,” Ambrose said. This disaster may have forced the ancestors of modern humans to adopt new cooperative strategies for survival that eventually permitted them to replace neandertals and other archaic human species, he said.
Merdeka.com-Village Sitoluama, district Laguboti, Toba Samosir Regency, North Sumatra, restless with unusual occurrences. The soil on the side of the House residents put out hot steam like gas and pungent-smelling.
The alleged harmful vapors showed up on Wednesday (27/5), the right side of the home page of Purasa, about ten kilometers from the Capital town of Balige, Toba Samosir Regency.
“Hot steam like gas and pungent smells coming out of the pores of the soil it is feared to threaten the safety of local people, so we report it to the authorities,” said one resident, Purasa Silalahi on Sitoluama, Saturday (30/5).
Indeed, advanced Purasa, since three weeks the temperature around her very hot, good day or night. In fact, any House floor ceramic tile feels hot.
Feeling suspicious, the conditions he intends to dig into the ground next to his house as deep as 50 centimeters and turns to steam heat with a temperature of smoke had emerged from the pit quarry. Due to fear of minerals with the condition that he immediately covered pit again.
“Hot steam and smells made us feel afraid of the gas that can be burned, so these findings are reported directly to the head of a local village,” explains Purasa.
The village chief Sitoluama, Moppo Old Pangaribuan said, hot steam that is troubling the citizens it has reported to the environmental protection agency of Toba Samosir.
The use, on its territory there has been research on 20 years ago and there is a sign or a PIN that there is oil in the area.
“First there was the research in this area. But the results to date there has been no certainty and now all of a sudden appear in the form of gas. We hope relevant agencies can examine repeated for convenience of society, “said Mappo.
Meanwhile, the Head of the environmental agency of Toba Samosir, Parulian Siregar said, his side has continued to report the discovery of the citizens over the discovery of the hot steam that is troubling.
“We tried to coordinate with the Central Department of mines and energy of North Sumatra as well as the relevant parties to know for sure the source of steam, including handling solutions,” Parulian said.
A supervolcanic eruption thought to have nearly driven humanity extinct may not have endangered the species after all, a new investigation suggests.
Supervolcanoes are capable of eruptions dwarfing anything ever seen in recorded history, expelling thousands of times more magma and ash than even a Mount St. Helens or Pinatubo. A supervolcanic eruption could wreak as much havoc as the impact of a mile-wide asteroid,by blotting out the sun with ash, reflecting its rays and cooling the Earth – a phenomenon called a “volcanic winter.” A dozen or so supervolcanoes exist today, some of them lying at the bottom of the sea.
The largest supervolcano eruption of the past 2.5 million years was a series of explosions of Mount Toba on the Indonesian island of Sumatra about 75,000 years ago. Researchers say Toba spewed out a staggering 700 cubic miles (2,800 cubic kilometers) of magma, equivalent in mass to more than 19 million Empire State Buildings. By comparison, the infamous blast from the volcanic Indonesian island of Krakatoa in 1883, one of the largest eruptions in recorded history, released about 3 cubic miles (12 cubic km) of magma.
About the same time the eruption took place, the number of modern humans apparently dropped cataclysmically, as shown by genetic research. People today evolved from the few thousand survivors of whatever befell humans in Africa at the time. The giant plume of ash from Toba stretched from the South China Sea to the Arabian Sea, and in the past investigators proposed the resulting volcanic winter might have caused this die-off. [Countdown: History’s Most Destructive Volcanoes]
However, recently scientists have suggested that Toba did not sway the course of human history as much as previously thought. For instance, prehistoric artifacts discovered in India and dating from after the eruption hinted that people coped fairly well with any effects of the eruption.
Now researchers have found that the evidence shows Toba didn’t actually cause a volcanic winter in East Africa where humans dwelled.
“We have been able to show that the largest volcanic eruption of the last two million years did not significantly alter the climate of East Africa,” said researcher Christine Lane, a geologist at the University of Oxford.
Ash in Africa
Lane and her colleagues examined ash from Toba recovered from mud extracted from two sites at the bottom of Lake Malawi, the second largest lake in the East African Rift Valley.
“We first started looking for the Toba ash a few years back, but it’s a bit like looking for a needle in a haystack, so it took a while,” Lane told OurAmazingPlanet. “Between myself and my co-author Ben Chorn, we systematically processed every centimeter of sediment between 24 to 46 meters [78 to 150 feet] depth in the central basin core. The layer is so small that if we leave any gaps in our search, we could miss it completely.”
Their analysis discovered that a thin layer of ash in this sediment about 90 feet (27 m) below the lake floor was from the last of the Toba eruptions, known as Youngest Toba Tuff.
“The Toba super-eruption dispersed huge volumes of ash across much of the Indian Ocean, Indian Peninsula and South China Sea,” Lane said. “We have discovered the layer of volcanic ash was carried about twice the distance as previously thought, over more than 7,000 kilometers [4,350 miles].”
The amount of ash found in the Malawi sediment core (a cylindrical log of sediment drilled from the ground), was more than the scientists expected to find.
“I was surprised to find so much ash in the Lake Malawi record,” Lane added. “The ash is very tiny, composed of shards of volcanic glass smaller than the diameter of a human hair. Nevertheless, in a lot of records I have worked on previously, even within just a few hundreds of miles of an eruption center, we sometimes only find less than 100 shards of glass within a gram of sediment. In Malawi, we have thousands of shards of glass per gram, which really shows how voluminous the Youngest Toba Tuff was.”
If the area had seen dramatic cooling because of all the ash spewed into the atmosphere, living matter near the lake surface would likely have died off, significantly altering the composition of the lake’s mud. However, when the researchers investigated algae and other organic matter from the layer that contained the ash from Toba, they saw no evidence of a significant temperature drop in East Africa. Apparently, “the environment very quickly recovered from any atmospheric disturbance that may have occurred,” Lane said.
But these results, detailed online April 29 in the journal Proceedings of the National Academy of Sciences, don’t mean that super-eruptions aren’t as big a risk to Earth’s denizens as previously suggested.
“It is important to realize that every volcanic eruption is different and the Youngest Toba Tuff provides only one example,” Lane said. “The impact of an eruption depends not just on the amount of ash erupted, but also the composition and volume of aerosols, how high in the atmosphere the ash is injected and the meteorological conditions at the time.”
As for what might explain the near-extinction humanity apparently once experienced, perhaps another kind of catastrophe, such as disease, hit the species. It may also be possible that such a disaster never happened in the first place – genetic research suggests modern humans descend from a single population of a few thousand survivors of a calamity, but another possible explanation is that modern humans descend from a few groups that left Africa at different times.
Future research will analyze what effects Toba may or may not have had on other lakes in East Africa.
“Whilst from this we can hypothesize that the global climatic impact was not as dramatic as some have suggested, we will need to find similarly high-resolution records of past climate from other regions that also contain Youngest Toba Tuff in order to definitively test this,” Lane said.