Toba supereruption unveils new insights into early human migration

Modern humans dispersed from Africa multiple times, but the event that led to global expansion occurred less than 100,000 years ago. Some researchers hypothesize that dispersals were restricted to "green corridors" formed during humid intervals when food was abundant and human populations expanded in lockstep with their environments. But a new study in Nature, including ASU researchers Curtis Marean, Christopher Campisano, and Jayde Hirniak, suggests that humans also may have dispersed during arid intervals along "blue highways" created by seasonal rivers. Researchers also found evidence of cooking and stone tools that represent the oldest evidence of archery.

Working in the Horn of Africa, researchers have uncovered evidence showing how early modern humans survived in the wake of the eruption of Toba, one of the largest supervolcanoes in history, some 74,000 years ago. The behavioral flexibility of these people not only helped them live through the supereruption but may have facilitated the later dispersal of modern humans out of Africa and across the rest of the world.

"This study confirms the results from Pinnacle Point in South Africa -- the eruption of Toba may have changed the environment in Africa, but people adapted and survived that eruption-caused environmental change," said Marean, research scientist with the Institute of Human Origins and Foundation Professor with the School of Human Evolution and Social Change.

The team investigated the Shinfa-Metema 1 site in the lowlands of present-day northwestern Ethiopia along the Shinfa River, a tributary of the Blue Nile River.

The supereruption occurred during the middle of the time when the site was occupied and is documented by tiny glass shards whose chemistry matches that of Toba.

Pinpoint timing through cryptotephra

"One of the ground-breaking implications of this study," said Marean, "is that with the new cryptotephra methods developed for our prior study in South Africa, and now applied here to Ethiopia, we can correlate sites across Africa, and perhaps the world, at a resolution of several weeks of time."

Cryptotephra are signature volcanic glass shards that can range from 80-20 microns in size, which is smaller than the diameter of a human hair. To extract these microscopic shards from archaeological sediment requires patience and great attention to detail.

"Searching for cryptotephra at these archaeological sites is like looking for a needle in a haystack, but not knowing if there is even a needle. However, having the ability to correlate sites 5,000 miles apart, and potentially further, to within weeks instead of thousands of years makes it all worth it," said Christopher Campisano, research scientist with the Institute of Human Origins and professor with the School of Human Evolution and Social Change.

"This study, once again," said Campisano, "highlights the importance of the University of Nevada-Las Vegas/Arizona State University team pushing the limits for successfully analyzing extremely low abundance cryptotephra to date and correlate archaeological sites across Africa."

The methods for identifying low abundance cryptotephra at Pinnacle Point were first developed at University of Nevada Las Vegas led by the late Gene Smith and Racheal Johnsen and now carried on at Arizona State University's Sediment and TEphra Preparation (STEP) Lab.

School of Human Evolution and Social Change graduate student Jayde Hirniak led ASU's effort to create its own cryptotephra lab -- the STEP Lab -- working with Campisano and building on methods developed at UNLV. Hirniak also collaborated with cryptotephra labs in the United Kingdom that work with sediment samples preserving hundreds or thousands of glass shards. Now Hirniak's primary expertise is in tephrochronology, which involves the use of volcanic ash to link archaeological and paleoenvironmental records and place them on the same timeline, which was her contribution to this research.

"Our lab at ASU was built to process extremely low abundance cryptotephra horizons (<10 shards per gram) using a highly specialized technique. There are only a few labs in the world with these capabilities," said Hirniak.

Migrations along "blue highways"

Based on isotope geochemistry of the teeth of fossil mammals and ostrich eggshells, they concluded that the site was occupied by humans during a time with long dry seasons on a par with some of the most seasonally arid habitats in East Africa today. Additional findings suggest that when river flows stopped during dry periods, people adapted by hunting animals that came to the remaining waterholes to drink. As waterholes continued to shrink, it became easier to capture fish without any special equipment, and diets shifted more heavily to fish.

Its climatic effects appear to have produced a longer dry season, causing people in the area to rely even more on fish. The shrinking of the waterholes may also have pushed humans to migrate outward in search of more food.

"As people depleted food in and around a given dry season waterhole, they were likely forced to move to new waterholes," said John Kappelman, a UT anthropology and earth and planetary sciences professor and lead author of the study. "Seasonal rivers thus functioned as 'pumps' that siphoned populations out along the channels from one waterhole to another, potentially driving the most recent out-of-Africa dispersal.

The humans who lived at Shinfa-Metema 1 are unlikely to have been members of the group that left Africa. However, the behavioral flexibility that helped them adapt to challenging climatic conditions such as the Toba supereruption was probably a key trait of Middle Stone Age humans that allowed our species to ultimately disperse from Africa and expand across the globe.

The people living in the Shinfa-Metema 1 site hunted a variety of terrestrial animals, from antelope to monkey, as attested to by cut marks on the bones, and apparently cooked their meals as shown by evidence of controlled fire at the site. The most distinctive stone tools are small, symmetrical triangular points. Analyses show that the points are most likely arrowheads that, at 74,000 years in age, represent the oldest evidence of archery.

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Threat of catastrophic supervolcano eruptions is ever-present

Curtin scientists are part of an international research team that studied an ancient supervolcano in Indonesia and found such volcanoes remain active and hazardous for thousands of years after a super-eruption, prompting the need for a rethink of how these potentially catastrophic events are predicted.

Associate Professor Martin Danišík, lead Australian author from the John de Laeter Centre based at Curtin University, said supervolcanoes often erupted several times with intervals of tens of thousands of years between the big eruptions but it was not known what happened during the dormant periods.

"Gaining an understanding of those lengthy dormant periods will determine what we look for in young active supervolcanoes to help us predict future eruptions," Associate Professor Danišík said.

"Super-eruptions are among the most catastrophic events in Earth's history, venting tremendous amounts of magma almost instantaneously. They can impact global climate to the point of tipping the Earth into a 'volcanic winter', which is an abnormally cold period that may result in widespread famine and population disruption.

"Learning how supervolcanoes work is important for understanding the future threat of an inevitable super-eruption, which happen about once every 17,000 years."

Associate Professor Danišík said the team investigated the fate of magma left behind after the Toba super-eruption 75,000 years ago, using the minerals feldspar and zircon, which contain independent records of time based on the accumulation of gasses argon and helium as time capsules in the volcanic rocks.

"Using these geochronological data, statistical inference and thermal modelling, we showed that magma continued to ooze out within the caldera, or deep depression created by the eruption of magma, for 5000 to 13,000 years after the super-eruption, and then the carapace of solidified left-over magma was pushed upward like a giant turtle shell," Associate Professor Danišík said.

"The findings challenged existing knowledge and studying of eruptions, which normally involves looking for liquid magma under a volcano to assess future hazard. We must now consider that eruptions can occur even if no liquid magma is found underneath a volcano -- the concept of what is 'eruptible' needs to be re-evaluated.

"While a super-eruption can be regionally and globally impactful and recovery may take decades or even centuries, our results show the hazard is not over with the super-eruption and the threat of further hazards exists for many thousands of years after.

"Learning when and how eruptible magma accumulates, and in what state the magma is in before and after such eruptions, is critical for understanding supervolcanoes."

Read more at Science Daily

Ample warning of supervolcano eruptions likely, experts say

Erupting volcano

Concern over the potential imminent eruptions of Earth's supervolcanoes, like Taupo in New Zealand or Yellowstone in the United States, may be quelled by the results of a new study suggesting that geological signs pointing to a catastrophic eruption would be clear far in advance.

To help forecast supervolcano eruptions, the study led by the University of Illinois has quantified the often-overlooked effects of tectonic stress on the rocks that house these sleeping giants, and suggests that people need not be quick to panic -- at least not yet.

In the study, researchers set out to investigate regional-scale tectonic stress and unexpectedly found that their models could help forecast supervolcano eruption timing and inform experts on what to expect, geologically, well before an eruption.

"Traditionally, it is thought that eruptions occur when the pressure caused by hot magma overtakes the strength of a volcano's roof rock," said geology professor Patricia Gregg. "But supervolcanoes tend to occur in areas of significant tectonic stress, where plates are moving toward, past or away from each other. That plate motion will affect model calculations."

Gregg, graduate student Haley Cabaniss and Pomona College geology professor Eric Grosfils published their findings in the journal Geophysical Research Letters.

The team created a model based on the Taupo Volcanic Zone in northern New Zealand. They chose this system because of its relatively uncomplicated extensional tectonic setting -- the type of area often associated with supervolcanoes. However, their models found that any tectonic stress would have a profound effect on the stability of supervolcanoes.

"It does not matter if it is extensional, compressional or shear stress," Cabaniss said. "Any tectonic stress will help destabilize rock and trigger eruptions, just on slightly different timescales. The remarkable thing we found is that the timing seems to depend not only on tectonic stress, but also on whether magma is being actively supplied to the volcano."

Using their model, the team looked at scenarios with different amounts of stress, tectonic plate movement and magma supply. They found that in any given tectonic setting, the magma reservoirs inside of supervolcanoes appear to remain stable for hundreds to thousands of years while new magma is being actively suppled to the system.

"We were initially surprised by this very short timeframe of hundreds to thousands of years," Gregg said. "But it is important to realize that supervolcanes can lay dormant for a very long time, sometimes a million years or more. In other words, they may remain stable, doing almost nothing for 999,000 years, then start a period of rejuvenation leading to a large-scale eruption."

Of course, panic sets in whenever Yellowstone or Taupo experience any change in seismic or geyser activity, but this research suggests that the precursors to catastrophic eruption will be far greater and long-lasting than anything yet documented, the researchers said.

"When new magma starts to rejuvenate a supervolcano system, we can expect to see massive uplift, faulting and earthquake activity," Gregg said. "Far greater than the meter-scale events we have seen in recent time. We are talking on the range of tens to hundreds of meters of uplift. Even then, our models predict that the system would inflate for hundreds to thousands of years before we witness catastrophic eruption."

Read more at Science Daily

The Future of Electric Vehicles May Lie Below Ancient Supervolcanoes

Wizard Island in Crater Lake, a caldera lake in Crater Lake National Park, Oregon

Lithium-ion batteries are the fuel source of the future, already powering nearly every electronic gadget in your house and soon most cars on the road. Volvo recently announced that all of its new models will be either hybrid or fully electric starting in 2019, and Chinese automaker BYD expects to have a completely electrified fleet in the next decade.

While global supplies of lithium are currently high, the expected surge in demand from electric carmakers could create a lithium shortage by as early as 2030.

More than 75 percent of the world’s lithium is mined in Chile and Australia, but geologists from Stanford University have discovered that vast stores of the valuable metal may be available at hundreds of sites across North America in the remains of ancient supervolcanoes.

In a paper published in Nature Communications, the researchers explained how these massive volcanoes — 10,000 times more powerful than most active volcanoes today — created the perfect thermodynamic conditions to produce thick deposits of lithium-rich clays.

“Lithium is the new oil,” lead author Thomas Benson, a recent Ph.D. graduate of Stanford’s School of Earth, Energy, and Environmental Sciences, told Seeker.

As the price of lithium goes up, it will become increasingly risky to allow just a handful of countries and companies to control the global lithium supply. By tapping lithium deposits in the calderas of extinct supervolcanoes, many more countries — including the US, Canada, and Mexico — can help diversify lithium production.

Supervolcano isn’t a true scientific term, Benson explained, but generally refers to a volcanic eruption that produces at least 1,000 cubic kilometers of material. For comparison, the eruption of Mount St. Helens in 1980 produced only 4.2 cubic kilometers of material.

The best-known supervolcano site in America is probably Crater Lake in Oregon. At nearly 2,000 feet deep, it’s the deepest lake in the nation, filling a six-mile wide caldera left by the colossal eruption and collapse of Mount Mazama 7,700 years ago.

But when geologists go looking for lithium, places like Crater Lake don’t cut it. What they need is a caldera lakebed that’s long been drained of its water.

That’s why the McDermitt volcanic field in Nevada is just the type of place where America’s lithium boom might begin. Located 60 miles northwest of Winnemucca, Nevada, the ancient caldera was formed from a supervolcanic eruption more than 16 million years and looks today like nothing more than a rocky wasteland. But just 30 meters below the surface lies a seam of sedimentary clays with lithium concentrations of greater than 4,000 parts per million.

“The magma that originally erupted from the supervolcano had about 1,400 ppm lithium in it,” said Benson, describing a red-hot pyroclastic flow of pumice, ash, crystals, and rock that spread for 50 miles in all directions. “That’s not crazy levels of enrichment, but since there was this big hole in the ground and you had 200,000 to 300,000 years, that lithium was progressively leached from the nearby rock by rainwater and deposited in the caldera lake sediments.”

Not all ancient caldera sediments are loaded with lithium. Benson and his colleagues analyzed tiny samples of crystallized magma called melt inclusions taken from supervolcano sites around the world. It turns out that the most lithium-rich magma is formed when a lot of continental crust is melted into the mix. Magma that’s mostly from the deeper mantle, however, doesn’t produce a lot of lithium, neither does magma melted from oceanic crust.

That’s why ancient magma samples from the Pantelleria caldera off the coast of Sicily showed only 100 ppm lithium, while the Hideaway Park supervolcano site in Colorado, sitting atop a thick layer of continental crust, registered at 5,990 ppm lithium on average. Even when the Crater Lake caldera does dry out hundreds of thousands of years from now, its near-coastal location would likely make it a lousy source of lithium.

The McDermitt volcanic site in Nevada is believed to be the largest lithium deposit in America with an estimated two megatons of the prized, but volatile metal. That’s a good cache, considering that the total amount of extractable lithium on the planet is estimated around 14 megatons.

Read more at Seeker