Earth’s most abundant mineral finally has a name

An ancient meteorite and high-energy X-rays have helped scientists conclude a half century of effort to find, identify and characterize a mineral that makes up 38 percent of the Earth.

And in doing so, a team of scientists led by Oliver Tschauner, a mineralogist at the University of Las Vegas, clarified the definition of the Earth’s most abundant mineral – a high-density form of magnesium iron silicate, now called Bridgmanite – and defined estimated constraint ranges for its formation. Their research was performed at the Advanced Photon Source, a U.S. Department of Energy (DOE) Office of Science User Facility located at DOE’s Argonne National Laboratory.

The mineral was named after 1964 Nobel laureate and pioneer of high-pressure research Percy Bridgman. The naming does more than fix a vexing gap in scientific lingo; it also will aid our understanding of the deep Earth.

To determine the makeup of the inner layers of the Earth, scientists need to test materials under extreme pressure and temperatures. For decades, scientists have believed a dense perovskite structure makes up 38 percent of the Earth’s volume, and that the chemical and physical properties of Bridgmanite have a large influence on how elements and heat flow through the Earth’s mantle. But since the mineral failed to survive the trip to the surface, no one has been able to test and prove its existence – a requirement for getting a name by the International Mineralogical Association.

Shock-compression that occurs in collisions of asteroid bodies in the solar system create the same hostile conditions of the deep Earth – roughly 2,100 degrees Celsius (3,800 degrees Farenheit) and pressures of about 240,000 times greater than sea-level air pressure. The shock occurs fast enough to inhibit the Bridgmanite breakdown that takes place when it comes under lower pressure, such as the Earth’s surface. Part of the debris from these collisions falls on Earth as meteorites, with the Bridgmanite “frozen” within a shock-melt vein. Previous tests on meteorites using transmission electron microscopy caused radiation damage to the samples and incomplete results.

So the team decided to try a new tactic: non-destructive micro-focused X-rays for diffraction analysis and novel fast-readout area-detector techniques. Tschauner and his colleagues from Caltech and the GeoSoilEnviroCARS, a University of Chicago-operated X-ray beamline at the APS at Argonne National Laboratory, took advantage of the X-rays’ high energy, which gives them the ability to penetrate the meteorite, and their intense brilliance, which leaves little of the radiation behind to cause damage.

The team examined a section of the highly shocked L-chondrite meteorite Tenham, which crashed in Australia in 1879. The GSECARS beamline was optimal for the study because it is one of the nation’s leading locations for conducting high-pressure research.

Bridgmanite grains are rare in the Tenhma meteorite, and they are smaller than 1 micrometer in diameter. Thus the team had to use a strongly focused beam and conduct highly spatially resolved diffraction mapping until an aggregate of Bridgmanite was identified and characterized by structural and compositional analysis.

This first natural specimen of Bridgmanite came with some surprises: It contains an unexpectedly high amount of ferric iron, beyond that of synthetic samples. Natural Bridgmanite also contains much more sodium than most synthetic samples. Thus the crystal chemistry of natural Bridgmanite provides novel crystal chemical insights. This natural sample of Bridgmanite may serve as a complement to experimental studies of deep mantle rocks in the future.

Prior to this study, knowledge about Bridgmanite’s properties has only been based on synthetic samples because it only remains stable below 660 kilometers (410 miles) depth at pressures of above 230 kbar (23 GPa). When it is brought out of the inner Earth, the lower pressures transform it back into less dense minerals. Some scientists believe that some inclusions on diamonds are the marks left by Bridgmanite that changed as the diamonds were unearthed.

The team’s results were published in the November 28 issue of the journal Science as “Discovery of bridgmanite, the most abundant mineral in Earth, in a shocked meteorite,” by O. Tschauner at University of Nevada in Las Vegas, N.V.; C. Ma; J.R. Beckett; G.R. Rossman at California Institute of Technology in Pasadena, Calif.; C. Prescher; V.B. Prakapenka at University of Chicago in Chicago, IL.

This research was funded by the U.S. Department of Energy, NASA, and NSF.

Massive geographic change may have triggered explosion of animal life

A new analysis from The University of Texas at Austin's Institute for Geophysics suggests a deep oceanic gateway, shown in blue, developed between the Pacific and Iapetus oceans immediately before the Cambrian sea level rise and explosion of life in the fossil record, isolating Laurentia from the supercontinent Gondwanaland. -  Ian Dalziel
A new analysis from The University of Texas at Austin’s Institute for Geophysics suggests a deep oceanic gateway, shown in blue, developed between the Pacific and Iapetus oceans immediately before the Cambrian sea level rise and explosion of life in the fossil record, isolating Laurentia from the supercontinent Gondwanaland. – Ian Dalziel

A new analysis of geologic history may help solve the riddle of the “Cambrian explosion,” the rapid diversification of animal life in the fossil record 530 million years ago that has puzzled scientists since the time of Charles Darwin.

A paper by Ian Dalziel of The University of Texas at Austin’s Jackson School of Geosciences, published in the November issue of Geology, a journal of the Geological Society of America, suggests a major tectonic event may have triggered the rise in sea level and other environmental changes that accompanied the apparent burst of life.

The Cambrian explosion is one of the most significant events in Earth’s 4.5-billion-year history. The surge of evolution led to the sudden appearance of almost all modern animal groups. Fossils from the Cambrian explosion document the rapid evolution of life on Earth, but its cause has been a mystery.

The sudden burst of new life is also called “Darwin’s dilemma” because it appears to contradict Charles Darwin’s hypothesis of gradual evolution by natural selection.

“At the boundary between the Precambrian and Cambrian periods, something big happened tectonically that triggered the spreading of shallow ocean water across the continents, which is clearly tied in time and space to the sudden explosion of multicellular, hard-shelled life on the planet,” said Dalziel, a research professor at the Institute for Geophysics and a professor in the Department of Geological Sciences.

Beyond the sea level rise itself, the ancient geologic and geographic changes probably led to a buildup of oxygen in the atmosphere and a change in ocean chemistry, allowing more complex life-forms to evolve, he said.

The paper is the first to integrate geological evidence from five present-day continents — North America, South America, Africa, Australia and Antarctica — in addressing paleogeography at that critical time.

Dalziel proposes that present-day North America was still attached to the southern continents until sometime into the Cambrian period. Current reconstructions of the globe’s geography during the early Cambrian show the ancient continent of Laurentia — the ancestral core of North America — as already having separated from the supercontinent Gondwanaland.

In contrast, Dalziel suggests the development of a deep oceanic gateway between the Pacific and Iapetus (ancestral Atlantic) oceans isolated Laurentia in the early Cambrian, a geographic makeover that immediately preceded the global sea level rise and apparent explosion of life.

“The reason people didn’t make this connection before was because they hadn’t looked at all the rock records on the different present-day continents,” he said.

The rock record in Antarctica, for example, comes from the very remote Ellsworth Mountains.

“People have wondered for a long time what rifted off there, and I think it was probably North America, opening up this deep seaway,” Dalziel said. “It appears ancient North America was initially attached to Antarctica and part of South America, not to Europe and Africa, as has been widely believed.”

Although the new analysis adds to evidence suggesting a massive tectonic shift caused the seas to rise more than half a billion years ago, Dalziel said more research is needed to determine whether this new chain of paleogeographic events can truly explain the sudden rise of multicellular life in the fossil record.

“I’m not claiming this is the ultimate explanation of the Cambrian explosion,” Dalziel said. “But it may help to explain what was happening at that time.”


To read the paper go to

Rare 2.5-billion-year-old rocks reveal hot spot of sulfur-breathing bacteria

Gold miners prospecting in a mountainous region of Brazil drilled this 590-foot cylinder of bedrock from the Neoarchaean Eon, which provides rare evidence of conditions on Earth 2.5 billion years ago. -  Alan J. Kaufman
Gold miners prospecting in a mountainous region of Brazil drilled this 590-foot cylinder of bedrock from the Neoarchaean Eon, which provides rare evidence of conditions on Earth 2.5 billion years ago. – Alan J. Kaufman

Wriggle your toes in a marsh’s mucky bottom sediment and you’ll probably inhale a rotten egg smell, the distinctive odor of hydrogen sulfide gas. That’s the biochemical signature of sulfur-using bacteria, one of Earth’s most ancient and widespread life forms.

Among scientists who study the early history of our 4.5 billion-year-old planet, there is a vigorous debate about the evolution of sulfur-dependent bacteria. These simple organisms arose at a time when oxygen levels in the atmosphere were less than one-thousandth of what they are now. Living in ocean waters, they respired (or breathed in) sulfate, a form of sulfur, instead of oxygen. But how did that sulfate reach the ocean, and when did it become abundant enough for living things to use it?

New research by University of Maryland geology doctoral student Iadviga Zhelezinskaia offers a surprising answer. Zhelezinskaia is the first researcher to analyze the biochemical signals of sulfur compounds found in 2.5 billion-year-old carbonate rocks from Brazil. The rocks were formed on the ocean floor in a geologic time known as the Neoarchaean Eon. They surfaced when prospectors drilling for gold in Brazil punched a hole into bedrock and pulled out a 590-foot-long core of ancient rocks.

In research published Nov. 7, 2014 in the journal Science, Zhelezinskaia and three co-authors–physicist John Cliff of the University of Western Australia and geologists Alan Kaufman and James Farquhar of UMD–show that bacteria dependent on sulfate were plentiful in some parts of the Neoarchaean ocean, even though sea water typically contained about 1,000 times less sulfate than it does today.

“The samples Iadviga measured carry a very strong signal that sulfur compounds were consumed and altered by living organisms, which was surprising,” says Farquhar. “She also used basic geochemical models to give an idea of how much sulfate was in the oceans, and finds the sulfate concentrations are very low, much lower than previously thought.”

Geologists study sulfur because it is abundant and combines readily with other elements, forming compounds stable enough to be preserved in the geologic record. Sulfur has four naturally occurring stable isotopes–atomic signatures left in the rock record that scientists can use to identify the elements’ different forms. Researchers measuring sulfur isotope ratios in a rock sample can learn whether the sulfur came from the atmosphere, weathering rocks or biological processes. From that information about the sulfur sources, they can deduce important information about the state of the atmosphere, oceans, continents and biosphere when those rocks formed.

Farquhar and other researchers have used sulfur isotope ratios in Neoarchaean rocks to show that soon after this period, Earth’s atmosphere changed. Oxygen levels soared from just a few parts per million to almost their current level, which is around 21 percent of all the gases in the atmosphere. The Brazilian rocks Zhelezinskaia sampled show only trace amounts of oxygen, a sign they were formed before this atmospheric change.

With very little oxygen, the Neoarchaean Earth was a forbidding place for most modern life forms. The continents were probably much drier and dominated by volcanoes that released sulfur dioxide, carbon dioxide, methane and other greenhouse gases. Temperatures probably ranged between 0 and 100 degrees Celsius (32 to 212 degrees Fahrenheit), warm enough for liquid oceans to form and microbes to grow in them.

Rocks 2.5 billion years old or older are extremely rare, so geologists’ understanding of the Neoarchaean are based on a handful of samples from a few small areas, such as Western Australia, South Africa and Brazil. Geologists theorize that Western Australia and South Africa were once part of an ancient supercontinent called Vaalbara. The Brazilian rock samples are comparable in age, but they may not be from the same supercontinent, Zhelezinskaia says.

Most of the Neoarchaean rocks studied are from Western Australia and South Africa and are black shale, which forms when fine dust settles on the sea floor. The Brazilian prospector’s core contains plenty of black shale and a band of carbonate rock, formed below the surface of shallow seas, in a setting that probably resembled today’s Bahama Islands. Black shale usually contains sulfur-bearing pyrite, but carbonate rock typically does not, so geologists have not focused on sulfur signals in Neoarchaean carbonate rocks until now.

Zhelezinskaia “chose to look at a type of rock that others generally avoided, and what she saw was spectacularly different,” said Kaufman. “It really opened our eyes to the implications of this study.”

The Brazilian carbonate rocks’ isotopic ratios showed they formed in ancient seabed containing sulfate from atmospheric sources, not continental rock. And the isotopic ratios also showed that Neoarchaean bacteria were plentiful in the sediment, respiring sulfate and emitted hydrogen sulfide–the same process that goes on today as bacteria recycle decaying organic matter into minerals and gases.

How could the sulfur-dependent bacteria have thrived during a geologic time when sulfur levels were so low? “It seems that they were in shallow water, where evaporation may have been high enough to concentrate the sulfate, and that would make it abundant enough to support the bacteria,” says Zhelezinskaia.

Zhelezinskaia is now analyzing carbonate rocks of the same age from Western Australia and South Africa, to see if the pattern holds true for rocks formed in other shallow water environments. If it does, the results may change scientists’ understanding of one of Earth’s earliest biological processes.

“There is an ongoing debate about when sulfate-reducing bacteria arose and how that fits into the evolution of life on our planet,” says Farquhar. “These rocks are telling us the bacteria were there 2.5 billion years ago, and they were doing something significant enough that we can see them today.”


This research was supported by the Fulbright Program (Grantee ID 15110620), the NASA Astrobiology Institute (Grant No. NNA09DA81A) and the National Science Foundation Frontiers in Earth-System Dynamics program (Grant No. 432129). The content of this article does not necessarily reflect the views of these organizations.

“Large sulfur isotope fractionations associated with Neoarchaean microbial sulfate reductions,” Iadviga Zhelezinskaia, Alan J. Kaufman, James Farquhar and John Cliff, was published Nov. 7, 2014 in Science. Download the abstract after 2 p.m. U.S. Eastern time, Nov. 6, 2014:

James Farquhar home page

Alan J. Kaufman home page

Iadviga Zhelezinskaia home page

Media Relations Contact: Abby Robinson, 301-405-5845,

Writer: Heather Dewar

Australian volcanic mystery explained: ANU media release

This is Dr. Rhodri Davies in the Raijin Supercomputer at The Australian National University. -  Stuart Hay, ANU
This is Dr. Rhodri Davies in the Raijin Supercomputer at The Australian National University. – Stuart Hay, ANU

Scientists have solved a long-standing mystery surrounding Australia’s only active volcanic area, in the country’s southeast.

The research explains a volcanic region that has seen more than 400 volcanic events in the last four million years. The 500 kilometre long region stretches from Melbourne to the South Australian town of Mount Gambier, which surrounds a dormant volcano that last erupted only 5,000 years ago.

“Volcanoes in this region of Australia are generated by a very different process to most of Earth’s volcanoes, which occur on the edges of tectonic plates, such as the Pacific Rim of Fire”, says lead researcher Dr Rhodri Davies, from the Research School of Earth Sciences.

“We have determined that the volcanism arises from a unique interaction between local variations in the continent’s thickness, which we were able to map for the first time, and its movement, at seven centimetres a year northwards towards New Guinea and Indonesia.

The volcanic area is comparatively shallow, less than 200 kilometres deep, in an area where a 2.5 billion year-old part of the continent meets a thinner, younger section, formed in the past 500 million years or so.

These variations in thickness drive currents within the underlying mantle, which draw heat from deeper up to the surface.

The researchers used state-of-the-art techniques to model these currents on the NCI Supercomputer, Raijin, using more than one million CPU hours.

“This boundary runs the length of eastern Australia, but our computer model demonstrates, for the first time, how Australia’s northward drift results in an isolated hotspot in this region,” Dr Davies said.

Dr Davies will now apply his research technique to other volcanic mysteries around the globe.

“There are around 50 other similarly isolated volcanic regions around the world, several of which we may now be able to explain,” he said.

It is difficult to predict where or when future eruptions might occur, Dr Davies said.

“There hasn’t been an eruption in 5,000 years, so there is no need to panic. However, the region is still active and we can’t rule out any eruptions in the future.”

Antarctic ice sheet is result of CO2 decrease, not continental breakup

Climate modelers from the University of New Hampshire have shown that the most likely explanation for the initiation of Antarctic glaciation during a major climate shift 34 million years ago was decreased carbon dioxide (CO2) levels. The finding counters a 40-year-old theory suggesting massive rearrangements of Earth’s continents caused global cooling and the abrupt formation of the Antarctic ice sheet. It will provide scientists insight into the climate change implications of current rising global CO2 levels.

In a paper published today in Nature, Matthew Huber of the UNH Institute for the Study of Earth, Oceans, and Space and department of Earth sciences provides evidence that the long-held, prevailing theory known as “Southern Ocean gateway opening” is not the best explanation for the climate shift that occurred during the Eocene-Oligocene transition when Earth’s polar regions were ice-free.

“The Eocene-Oligocene transition was a major event in the history of the planet and our results really flip the whole story on its head,” says Huber. “The textbook version has been that gateway opening, in which Australia pulled away from Antarctica, isolated the polar continent from warm tropical currents, and changed temperature gradients and circulation patterns in the ocean around Antarctica, which in turn began to generate the ice sheet. We’ve shown that, instead, CO2-driven cooling initiated the ice sheet and that this altered ocean circulation.”

Huber adds that the gateway theory has been supported by a specific, unique piece of evidence-a “fingerprint” gleaned from oxygen isotope records derived from deep-sea sediments. These sedimentary records have been used to map out gradient changes associated with ocean circulation shifts that were thought to bear the imprint of changes in ocean gateways.

Although declining atmospheric levels of CO2 has been the other main hypothesis used to explain the Eocene-Oligocene transition, previous modeling efforts were unsuccessful at bearing this out because the CO2 drawdown does not by itself match the isotopic fingerprint. It occurred to Huber’s team that the fingerprint might not be so unique and that it might also have been caused indirectly from CO2 drawdown through feedbacks between the growing Antarctic ice sheet and the ocean.

Says Huber, “One of the things we were always missing with our CO2 studies, and it had been missing in everybody’s work, is if conditions are such to make an ice sheet form, perhaps the ice sheet itself is affecting ocean currents and the climate system-that once you start getting an ice sheet to form, maybe it becomes a really active part of the climate system and not just a passive player.”

For their study, Huber and colleagues used brute force to generate results: they simply modeled the Eocene-Oligocene world as if it contained an Antarctic ice sheet of near-modern size and shape and explored the results within the same kind of coupled ocean-atmosphere model used to project future climate change and across a range of CO2 values that are likely to occur in the next 100 years (560 to 1200 parts per million).

“It should be clear that resolving these two very different conceptual models for what caused this huge transformation of the Earth’s surface is really important because today as a global society we are, as I refer to it, dialing up the big red knob of carbon dioxide but we’re not moving continents around.”

Just what caused the sharp drawdown of CO2 is unknown, but Huber points out that having now resolved whether gateway opening or CO2 decline initiated glaciation, more pointed scientific inquiry can be focused on answering that question.

Huber notes that despite his team’s finding, the gateway opening theory won’t now be shelved, for that massive continental reorganization may have contributed to the CO2 drawdown by changing ocean circulation patterns that created huge upwellings of nutrient-rich waters containing plankton that, upon dying and sinking, took vast loads of carbon with them to the bottom of the sea.

Victoria’s volcano count rises

Geologists have discovered three previously unrecorded volcanoes in volcanically active southeast Australia.

The new Monash University research, published in the Australian Journal of Earth Sciences, gives a detailed picture of an area of volcanic centres already known to geologists in the region.

Covering an area of 19,000 square kilometres in Victoria and South Australia, with over 400 volcanoes, the Newer Volcanics Province (NVP) features the youngest volcanoes in Australia including Mount Schank and Mount Gambier.

Focusing on the Hamilton region, lead researcher Miss Julie Boyce from the School of Geosciences said the surprising discovery means additional volcanic centres may yet be discovered in the NVP.

“Victoria’s latest episode of volcanism began about eight million years ago, and has helped to shape the landscape. The volcanic deposits, including basalt, are among the youngest rocks in Victoria but most people know little about them,”Miss Boyce said.

“Though it’s been more than 5000 years since the last volcanic eruption in Australia, it’s important that we understand where, when and how these volcanoes erupted. The province is still active, so there may be future eruptions.”

The largest unrecorded volcano is a substantial maar-cone volcanic complex – a broad, low relief volcanic crater caused by an explosion when groundwater comes into contact with hot magma – identified 37 kilometres east of Hamilton.

Miss Boyce said the discoveries were made possible only by analysing a combination of satellite photographs, detailed NASA models of the topography of the area and the distribution of magnetic minerals in the rocks, alongside site visits to build a detailed picture of the Hamilton region of the NVP.

“Traditionally, volcanic sites are analysed by one or two of these techniques. This is the first time that this multifaceted approach has been applied to the NVP and potentially it could be used to study other volcanic provinces worldwide.”

The NVP is considered active, as carbon dioxide is released from the Earth’s mantle in several areas, where there is a large heat anomaly at depth. With an eruption frequency of one volcano every 10,800 years or less, future eruptions may yet occur.

It’s hoped that this multifaceted approach will lead to a better understanding of the distribution and nature of volcanism, allowing for more accurate hazard analysis and risk estimates for future eruptions.

Australia’s deadly eruptions the reason for the first mass extinction

A Curtin University researcher has shown that ancient volcanic eruptions in Australia 510 million years ago significantly affected the climate, causing the first known mass extinction in the history of complex life.

Published in prestigious journal Geology, Curtin’s Associate Professor Fred Jourdan, along with colleagues from several Australian and international institutions, used radioactive dating techniques to precisely measure the age of the eruptions of the Kalkarindji volcanic province.

Dr Jourdan and his team were able to prove the volcanic province occurred at the same time as the Early-Middle Cambrian extinction from 510-511 million years ago – the first extinction to wipe out complex multicellular life.

“It has been well-documented that this extinction, which eradicated 50 per cent of species, was related to climatic changes and depletion of oxygen in the oceans, but the exact mechanism causing these changes was not known, until now,” Dr Jourdan said.

“Not only were we able to demonstrate that the Kalkarindji volcanic province was emplaced at the exact same time as the Cambrian extinction, but were also able to measure a depletion of sulphur dioxide from the province’s volcanic rocks – which indicates sulphur was released into the atmosphere during the eruptions.

“As a modern comparison, when the small volcano Pinatubo erupted in 1991, the resulting discharge of sulphur dioxide decreased the average global temperatures by a few tenths of a degree for a few years following the eruption.

“If relatively small eruptions like Pinatubo can affect the climate just imagine what a volcanic province with an area equivalent to the size of the state of Western Australia can do.”

The team then compared the Kalkarindji volcanic province with other volcanic provinces and showed the most likely process for all the mass extinctions was a rapid oscillation of the climate triggered by volcanic eruptions emitting sulphur dioxide, along with greenhouse gases methane and carbon dioxide.

“We calculated a near perfect chronological correlation between large volcanic province eruptions, climate shifts and mass extinctions over the history of life during the last 550 million years, with only one chance over 20 billion that this correlation is just a coincidence,” Dr Jourdan said.

Dr Jourdan said the rapid oscillations of the climate produced by volcanic eruptions made it difficult for various species to adapt, ultimately resulting in their demise. He also stressed the importance of this research to better understand our current environment.

“To comprehend the long-term climatic and biological effects of the massive injections of gas in the atmosphere by modern society, we need to recognise how climate, oceans and ecosytems were affected in the past,” he said.

Scientists reconstruct ancient impact that dwarfs dinosaur-extinction blast

A graphical representation of the size of the asteroid thought to have killed the dinosaurs, and the crater it created, compared to an asteroid thought to have hit the Earth 3.26 billion years ago and the size of the crater it may have generated. A new study reveals the power and scale of the event some 3.26 billion years ago which scientists think created geological features found in a South African region known as the Barberton greenstone belt. -  American Geophysical Union
A graphical representation of the size of the asteroid thought to have killed the dinosaurs, and the crater it created, compared to an asteroid thought to have hit the Earth 3.26 billion years ago and the size of the crater it may have generated. A new study reveals the power and scale of the event some 3.26 billion years ago which scientists think created geological features found in a South African region known as the Barberton greenstone belt. – American Geophysical Union

Picture this: A massive asteroid almost as wide as Rhode Island and about three to five times larger than the rock thought to have wiped out the dinosaurs slams into Earth. The collision punches a crater into the planet’s crust that’s nearly 500 kilometers (about 300 miles) across: greater than the distance from Washington, D.C. to New York City, and up to two and a half times larger in diameter than the hole formed by the dinosaur-killing asteroid. Seismic waves bigger than any recorded earthquakes shake the planet for about half an hour at any one location – about six times longer than the huge earthquake that struck Japan three years ago. The impact also sets off tsunamis many times deeper than the one that followed the Japanese quake.

Although scientists had previously hypothesized enormous ancient impacts, much greater than the one that may have eliminated the dinosaurs 65 million years ago, now a new study reveals the power and scale of a cataclysmic event some 3.26 billion years ago which is thought to have created geological features found in a South African region known as the Barberton greenstone belt. The research has been accepted for publication in Geochemistry, Geophysics, Geosystems, a journal of the American Geophysical Union.

The huge impactor – between 37 and 58 kilometers (23 to 36 miles) wide – collided with the planet at 20 kilometers per second (12 miles per second). The jolt, bigger than a 10.8 magnitude earthquake, propelled seismic waves hundreds of kilometers through the Earth, breaking rocks and setting off other large earthquakes. Tsunamis thousands of meters deep – far bigger than recent tsunamis generated by earthquakes — swept across the oceans that covered most of the Earth at that time.

“We knew it was big, but we didn’t know how big,” Donald Lowe, a geologist at Stanford University and a co-author of the study, said of the asteroid.

Lowe, who discovered telltale rock formations in the Barberton greenstone a decade ago, thought their structure smacked of an asteroid impact. The new research models for the first time how big the asteroid was and the effect it had on the planet, including the possible initiation of a more modern plate tectonic system that is seen in the region, according to Lowe.

The study marks the first time scientists have mapped in this way an impact that occurred more than 3 billion years ago, Lowe added, and is likely one of the first times anyone has modeled any impact that occurred during this period of the Earth’s evolution.

The impact would have been catastrophic to the surface environment. The smaller, dino-killing asteroid crash is estimated to have released more than a billion times more energy than the bombs that destroyed Hiroshima and Nagasaki. The more ancient hit now coming to light would have released much more energy, experts said.

The sky would have become red hot, the atmosphere would have been filled with dust and the tops of oceans would have boiled, the researchers said. The impact sent vaporized rock into the atmosphere, which encircled the globe and condensed into liquid droplets before solidifying and falling to the surface, according to the researchers.

The impact may have been one of dozens of huge asteroids that scientists think hit the Earth during the tail end of the Late Heavy Bombardment period, a major period of impacts that occurred early in the Earth’s history – around 3 billion to 4 billion years ago.

Many of the sites where these asteroids landed were destroyed by erosion, movement of the Earth’s crust and other forces as the Earth evolved, but geologists have found a handful of areas in South Africa, and Western Australia that still harbor evidence of these impacts that occurred between 3.23 billion and 3.47 billion years ago. The study’s co-authors think the asteroid hit the Earth thousands of kilometers away from the Barberton Greenstone Belt, although they can’t pinpoint the exact location.

“We can’t go to the impact sites. In order to better understand how big it was and its effect we need studies like this,” said Lowe. Scientists must use the geological evidence of these impacts to piece together what happened to the Earth during this time, Lowe said.

The study’s findings have important implications for understanding the early Earth and how the planet formed. The impact may have disrupted the Earth’s crust and the tectonic regime that characterized the early planet, leading to the start of a more modern plate tectonic system, according to the paper’s co-authors.

The pummeling the planet endured was “much larger than any ordinary earthquake,” said Norman Sleep, a physicist at Stanford University and co-author of the study. He used physics, models, and knowledge about the formations in the Barberton greenstone belt, other earthquakes and other asteroid impact sites on the Earth and the moon to calculate the strength and duration of the shaking that the asteroid produced. Using this information, Sleep recreated how waves traveled from the impact site to the Barberton greenstone belt and caused the geological formations.

The geological evidence found in the Barberton that the paper investigates indicates that the asteroid was “far larger than anything in the last billion years,” said Jay Melosh, a professor at Purdue University in West Lafayette, Indiana, who was not involved in the research.

The Barberton greenstone belt is an area 100 kilometers (62 miles) long and 60 kilometers (37 miles) wide that sits east of Johannesburg near the border with Swaziland. It contains some of the oldest rocks on the planet.

The model provides evidence for the rock formations and crustal fractures that scientists have discovered in the Barberton greenstone belt, said Frank Kyte, a geologist at UCLA who was not involved in the study.

“This is providing significant support for the idea that the impact may have been responsible for this major shift in tectonics,” he said.

Reconstructing the asteroid’s impact could also help scientists better understand the conditions under which early life on the planet evolved, the paper’s authors said. Along with altering the Earth itself, the environmental changes triggered by the impact may have wiped out many microscopic organisms living on the developing planet, allowing other organisms to evolve, they said.

“We are trying to understand the forces that shaped our planet early in its evolution and the environments in which life evolved,” Lowe said.

Global map to predict giant earthquakes

A team of international researchers, led by Monash University’s Associate Professor Wouter Schellart, have developed a new global map of subduction zones, illustrating which ones are predicted to be capable of generating giant earthquakes and which ones are not.

The new research, published in the journal Physics of the Earth and Planetary Interiors, comes nine years after the giant earthquake and tsunami in Sumatra in December 2004, which devastated the region and many other areas surrounding the Indian Ocean, and killed more than 200,000 people.

Since then two other giant earthquakes have occurred at subduction zones, one in Chile in February 2010 and one in Japan in March 2011, which both caused massive destruction, killed many thousands of people and resulted in billions of dollars of damage.

Most earthquakes occur at the boundaries between tectonic plates that cover the Earth’s surface. The largest earthquakes on Earth only occur at subduction zones, plate boundaries where one plate sinks (subducts) below the other into the Earth’s interior. So far, seismologists have recorded giant earthquakes for only a limited number of subduction zone segments. But accurate seismological records go back to only ~1900, and the recurrence time of giant earthquakes can be many hundreds of years.

“The main question is, are all subduction segments capable of generating giant earthquakes, or only some of them? And if only a limited number of them, then how can we identify these,” Dr Schellart said.

Dr Schellart, of the School of Geosciences, and Professor Nick Rawlinson from the University of Aberdeen in Scotland used earthquake data going back to 1900 and data from subduction zones to map the main characteristics of all active subduction zones on Earth. They investigated if those subduction segments that have experienced a giant earthquake share commonalities in their physical, geometrical and geological properties.

They found that the main indicators include the style of deformation in the plate overlying the subduction zone, the level of stress at the subduction zone, the dip angle of the subduction zone, as well as the curvature of the subduction zone plate boundary and the rate at which it moves.

Through these findings Dr Schellart has identified several subduction zone regions capable of generating giant earthquakes, including the Lesser Antilles, Mexico-Central America, Greece, the Makran, Sunda, North Sulawesi and Hikurangi.

“For the Australian region subduction zones of particular significance are the Sunda subduction zone, running from the Andaman Islands along Sumatra and Java to Sumba, and the Hikurangi subduction segment offshore the east coast of the North Island of New Zealand. Our research predicts that these zones are capable of producing giant earthquakes,” Dr Schellart said.

“Our work also predicts that several other subduction segments that surround eastern Australia (New Britain, San Cristobal, New Hebrides, Tonga, Puysegur), are not capable of producing giant earthquakes.”

X-ray vision to detect unseen gold

Powerful x-rays can now be used to rapidly and accurately detect gold in ore samples, thanks to a new technique developed by CSIRO – a move that could save Australia’s minerals industry hundreds of millions of dollars each year.

CSIRO has conducted a pilot study that shows that gamma-activation analysis (GAA) offers a much faster, more accurate way to detect gold than traditional chemical analysis methods.

This will mean mining companies can measure what’s coming in and out of their processing plants with greater accuracy, allowing them to monitor process performance and recover small traces of gold – worth millions of dollars – that would otherwise be discarded.

GAA works by scanning mineral samples – typically weighing around half a kilogram – using high-energy x-rays similar to those used to treat patients in hospitals. The x-rays activate any gold in the sample, and the activation is then picked up using a sensitive detector.

According to project leader Dr James Tickner, CSIRO’s study showed that this method is two-to-three times more accurate than the standard industry technique ‘fire assay’, which requires samples to be heated up to 1200°C.

“The big challenge for this project was to push the sensitivity of GAA to detect gold at much lower levels – well below a threshold of one gram per tonne,” he says.

Dr Tickner explains that a gold processing plant may only recover between 65 and 85 per cent of gold present in mined rock. Given a typical plant produces around A$1 billion of gold each year, this means hundreds of millions of dollars worth of gold is going to waste.

“Our experience suggests that better process monitoring can help reduce this loss by about a third,” he says.

Last year, Australia produced over A$10 billion worth of gold. Even if GAA only led to a modest 5 per cent improvement in recovery, that would be worth half a billion dollars annually to the industry.

Dr Tickner says that the other major benefit of GAA is that it is easily automated, allowing for much quicker analysis of ore samples.

“Fire assay usually involves sending samples off to a central lab and waiting several days for the results. Using GAA we can do the analysis in a matter of minutes, allowing companies to respond much more quickly to the data they’re collecting.”

“A compact GAA facility could even be trucked out to remote sites for rapid, on-the-spot analysis.”

Another great advantage of GAA is that it is more sustainable – unlike fire assay it doesn’t require the use of heavy metals such as lead.

It is also very adaptable. “While most of the work we’ve done has been based on the gold industry, the technique can be modified for other valuable commodities such as silver, lead, zinc, tin, copper and the platinum group metals.”

Now that the research team has proved the effectiveness of the technique, their next goal is to partner with local and international companies in order to get a full-scale analysis facility up and running in Australia. They hope to achieve this within the next two years.