Geochemical Detectives Use Lab Mimicry To Look Back In Time

New work from a research team led by Carnegie’s Anat Shahar contains some unexpected findings about iron chemistry under high-pressure conditions, such as those likely found in the Earth’s core, where iron predominates and creates our planet’s life-shielding magnetic field. Their results, published in Science, could shed light on Earth’s early days when the core was formed through a process called differentiation–when the denser materials, like iron, sunk inward toward the center, creating the layered composition the planet has today.

earth

Earth formed from accreted matter surrounding the young Sun. Over time, the iron in this early planetary material moved inward, separating from the surrounding silicate. This process created the planet’s iron core and silicate upper mantle. But much about this how this differentiation process occurred is still poorly understood, due to the technological impossibility of taking samples from the Earth’s core to see which compounds exist there.

Seismic data show that in addition to iron, there are “lighter” elements present in the core, but which elements and in what concentrations they exist has been a matter of great debate. This is because as the iron moved inward toward the core, it interacted with various lighter elements to form different alloyed compounds, which were then carried along with the iron into the planet’s depths.

Which elements iron bonded with during this time would have been determined by the surrounding conditions, including pressure and temperature. As a result, working backward and determining which iron alloy compounds were created during differentiation could tell scientists about the conditions on early Earth and about the planet’s geochemical evolution.

The team–including Carnegie’s Jinfu Shu and Yuming Xiao–decided to investigate this subject by researching how pressures mimicking the Earth’s core would affect the composition of iron isotopes in various alloys of iron and light elements. Isotopes are versions of an element where the number of neutrons differs from the number of protons. (Each element contains a unique number of protons.)

Because of this accounting difference, isotopes’ masses are not the same, which can sometimes cause small variations in how different isotopes of the same element are partitioned in, or are “picked up” by, either silicate or iron metal. Some isotopes are preferred by certain reactions, which results in an imbalance in the proportion of each isotope incorporated into the end products of these reactions–a process that can leave behind trace isotopic signatures in rocks. This phenomenon is called isotope fractionation and is crucial to the team’s research.

Before now, pressure was not considered a critical variable affecting isotope fractionation. But Shahar and her team’s research demonstrated that for iron, extreme pressure conditions do affect isotope fractionation.

More importantly, the team discovered that due to this high-pressure fractionation, reactions between iron and two of the light elements often considered likely to be present in the core–hydrogen and carbon–would have left behind an isotopic signature in the mantle silicate as they reacted with iron and sunk to the core. But this isotopic signature has not been found in samples of mantle rock, so scientists can exclude them from the list of potential light elements in the core.

Oxygen, on the other hand, would not have left an isotopic signature behind in the mantle, so it is still on the table. Likewise, other potential core light elements still need to be investigated, including silicon and sulfur.

“What does this mean? It means we are gaining a better understanding of our planet’s chemical and physical history,” Shahar explained. “Although Earth is our home, there is still so much about its interior that we don’t understand. But evidence that extreme pressures affect how isotopes partition, in ways that we can see traces of in rock samples, is a huge step forward in learning about our planet’s geochemical evolution.”

Scientists Inch Closer to Predicting Phreatic Volcanic Eruptions

One type of a volcanic eruption, a phreatic (steam) eruption, which involves external water, is particularly energetic causing a disproportionate number of fatalities. Throughout the centuries, volcanic eruptions have claimed hundreds of thousands of lives due in part to the lack of accurate signs indicating imminent eruptions. Phreatic eruptions are extremely difficult to forecast, often occurring with little or no geophysical precursors.

phreatic eruptions1

Recently, researchers at the Deep Carbon Observatory (DCO), led by Maarten de Moor from the Observatorio Vulcanológico y Sismológico de Costa Rica, Universidad Nacional, Heredia, Costa Rica, (and postdoc at UNM) along with University of New Mexico Professor Tobias Fischer, Department of Planetary Sciences and chair of the Deep Earth Carbon Degassing initiative, measured gas emissions from crater lake at Poás volcano in Costa Rica, in an attempt to determine some of the precursors to major volcanic eruptions.

“The initial goal of the study was to quantify gas fluxes (CO2, SO2, H2S) from Poas volcano and to monitor changes in gas compositions,” said de Moor. “The motivation behind the measurements was firstly to provide robust constraints on gas fluxes as a contribution to global volcanic gas emissions to the atmosphere, and secondly to monitor degassing in order to track volcanic activity for hazard mitigation purposes.”

Excerpt from EPSL paper: “The Poás crater represents one of the most chemically extreme environments on Earth and Poás Volcano National Park was visited by more than 200,000 tourists in 2014. About 60 seismically registered phreatic blasts occurred from the lake during the same year, ranging from minor “gas bursts” to highly explosive jets ejecting ballistics, sediments, vapor and lake water to more than 400 meters above the lake surface. ”

In a new article, published in Earth and Planetary Science Letters recently, the results from a DECADE (Deep Earth Carbon Degassing initiative) project to investigate gas emissions at Poás have delivered promising results.

“Before this study, phreatic eruptions were primarily thought to be generated by changes in hydrothermal systems, and usually occur with no appreciable precursors,” said de Moor. “Our study shows that there are clear short-term changes in gas compositions prior to phreatic eruptions at Poás, and are generated by short-period changes in high temperature volcanic gas input from the deep magmatic system.”

The team measured gas emissions from the crater lake in situ using a fixed multiple gas analyzer station (Multi-GAS) during a two month period of phreatic activity in 2014. The lake was the site of intense phreatic eruptive behavior between 2006 and 2014.

Both accuracy and precision are important in the Multi-GAS measurements. The Multi-GAS instrument measures gas ratios, such as SO2/ CO2 and H2S / SO2. Precision, or the reproducibility, of the Multi-GAS measurements is important when comparing data points within the researchers’ dataset.

“The accuracy, or proximity of the measured value to the true gas ratio, is most important for quantifying gas emission rates from the volcano and for comparing our measured gas compositions to those from other volcanoes or other studies at Poas,” said de Moor. “We did a series of laboratory tests using gas mixtures to estimate both accuracy and precision of the Multi-GAS measurements. These measurements give us confidence that the variations we see in the field data are real.”

“Diagnostic tests prove that the occurrence of eruptions and high SO2/ CO2 are statistically correlated, and that the occurrence of quiescence (no eruptions) and low SO2/ CO2 are also correlated. The results of these diagnostic tests from Poás show scientists that both true predicted values (successful “prediction” of eruption based on high SO2/CO2) and false predicted values (successful “prediction” of quiescence based on low SO2/CO2) are high, indicating strong evidential worth for the association between gas composition and eruptions.”

The gas composition data show significant variations in the ratio between SO2 and CO2, which are statistically correlated with both the occurrence and the size of phreatic eruptions. The scientists found that the composition of gas emitted directly from the lake approaches that of magmatic gas days before large phreatic eruptions.

“The changes in gas chemistry are due to the susceptibility of different gas species to reaction with hydrothermal fluids,” explained de Moor. “CO2 is essentially inert in ultra-acidic conditions and therefore passes through the hydrothermal system and acid lake with minimal modification. In contrast, SO2 is partially removed from the gas phase by hydrothermal reactions producing aqueous bisulfate and liquid/solid native sulfur.”

Excerpt from DCO report: “Gas flux measurements conducted using mini-DOAS (differential optical absorption spectroscopy) show that high emission rates of SO2 from the lake occur during eruptive activity and are also associated with high SO2/CO2.”

“We argued that the efficiency of S removal from the gas is inhibited with increasing gas flux through the hydrothermal system, resulting in increasing SO2/ CO2,” de Moor said. “Importantly, the results suggest that short-period pulses of magmatic gas and heat are directly responsible for generating individual phreatic eruptions.”

Excerpt from DCO report: “These promising results show that high-frequency gas monitoring may provide an effective means of forecasting phreatic eruptions. The biggest challenge to this monitoring approach is maintaining the Multi-GAS instrument in extremely harsh conditions. Peripheral components of the station were destroyed by a large eruption in June 2014, which spelled the end of the lake gas emission experiment. However, the instrument survived and is currently monitoring changes in fumarole gas composition.”

“My main concern is simply trying to keeping these instruments running at active volcanoes, because they are constantly being damaged by toxic gases and eruptions,” said de Moor. “If we can acquire good time-series data, we will learn a lot more about how volcanoes work, why they erupt, and how to predict explosions.

“There are still many things scientists do not know about the interactions between magmatic gases and hydrothermal systems. This study shows in particular that kinetics are very important in these systems. Most geochemical models that are used to understand volcanic degassing assume equilibrium conditions. ”

“Volcanoes are perhaps the most dynamic physical and chemical systems on Earth,” said de Moor. “Once we accept that kinetic factors are often more influential than equilibrium conditions, we will come closer to understanding volcanic degassing processes.”

JUST IN: New Maps Chart Mantle Plumes Melting Greenland Glaciers

Many large glaciers in Greenland are at greater risk of melting from below than previously thought, according to new maps of the seafloor around Greenland created by an international research team. Like other recent research findings, the maps highlight the critical importance of studying the seascape under Greenland’s coastal waters to better understand and predict global sea level rise.

Uummannaq fjord

Researchers from the University of California, Irvine; NASA’s Jet Propulsion Laboratory, Pasadena, California; and other research institutions combined all observations their various groups had made during shipboard surveys of the seafloors in the Uummannaq and Vaigat fjords in west Greenland between 2007 and 2014 with related data from NASA’s Operation Icebridge and the NASA/U.S. Geological Survey Landsat satellites. They used the combined data to generate comprehensive maps of the ocean floor around 14 Greenland glaciers. Their findings show that previous estimates of ocean depth in this area were as much as several thousand feet too shallow.

Why does this matter? Because glaciers that flow into the ocean melt not only from above, as they are warmed by Sun and air, but from below, as they are warmed by water.

Iceland - Greenland Mid-Atlantic Ridge3

In most of the world, a deeper seafloor would not make much difference in the rate of melting, because typically ocean water is warmer near the surface and colder below. But Greenland is exactly the opposite. Surface water down to a depth of almost a thousand feet (300 meters) comes mostly from Arctic river runoff. This thick layer of frigid, fresher water is only 33 to 34 degrees Fahrenheit (1 degree Celsius). Below it is a saltier layer of warmer ocean water. This layer is currently more than 5 degrees F (3 degrees C) warmer than the surface layer, and climate models predict its temperature could increase another 3.6 degrees F (2 degrees C) by the end of this century.

About 90 percent of Greenland’s glaciers flow into the ocean, including the newly mapped ones. In generating estimates of how fast these glaciers are likely to melt, researchers have relied on older maps of seafloor depth that show the glaciers flowing into shallow, cold seas. The new study shows that the older maps were wrong.

“While we expected to find deeper fjords than previous maps showed, the differences are huge,” said Eric Rignot of UCI and JPL, lead author of a paper on the research. “They are measured in hundreds of meters, even one kilometer [3,300 feet] in one place.” The difference means that the glaciers actually reach deeper, warmer waters, making them more vulnerable to faster melting as the oceans warm.

Co-author Ian Fenty of JPL noted that earlier maps were based on sparse measurements mostly collected several miles offshore. Mapmakers assumed that the ocean floor sloped upward as it got nearer the coast. That’s a reasonable supposition, but it’s proving to be incorrect around Greenland.

Rignot and Fenty are co-investigators in NASA’s five-year Oceans Melting Greenland (OMG) field campaign, which is creating similar charts of the seafloor for the entire Greenland coastline. Fenty said that OMG’s first mapping cruise last summer found similar results. “Almost every glacier that we visited was in waters that were far, far deeper than the maps showed.”

The researchers also found that besides being deeper overall, the seafloor depth is highly variable. For example, the new map revealed one pair of side-by-side glaciers whose bottom depths vary by about 1,500 feet (500 meters). “These data help us better interpret why some glaciers have reacted to ocean warming while others have not,” Rignot said.

The lack of detailed maps has hampered climate modelers like Fenty who are attempting to predict the melting of the glaciers and their contribution to global sea level rise. “The first time I looked at this area and saw how few data were available, I just threw my hands up,” Fenty said. “If you don’t know the seafloor depth, you can’t do a meaningful simulation of the ocean circulation.”

BREAKING NEWS: Volcanoes Responsible for Climate Change Through Much of Earth’s History

A new study in the April 22 edition of the journal ‘Science’, reveals that volcanic activity associated with the plate-tectonic movement of continents may be responsible for climatic shifts from hot to cold throughout much of Earth’s history. The study, led by researchers at The University of Texas at Austin Jackson School of Geosciences, addresses why Earth has fluctuated from periods when the planet was covered in ice to times when polar regions were ice-free.

volcanic arc

Lead researcher Ryan McKenzie said the team found that periods when volcanoes along continental arcs were more active coincided with warmer trends over the past 720 million years. Conversely, periods when continental arc volcanoes were less active coincided with colder, or cooling trends.

For this study, researchers looked at the uranium-lead crystallization ages of the mineral zircon, which is largely created during continental volcanic arc activity. They looked at data for roughly 120,000 zircon grains from thousands of samples across the globe.

zircon and mantle

Zircon is often associated with mantle plumes. If the zircon Hf model age is very close to its formation age (zircon U–Pb) – the magma could be subsequent of a depleted mantle plume. On the other hand, if the zircon Hf model age is older than its formation age, it can be concluded that the magma was derived from enriched mantle sources or was contaminated by crustal materials.

“We’re looking at changes in zircon production on various continents throughout Earth’s history and seeing how the changes correspond with the various cooling and warming trends,” McKenzie said. “Ultimately, we find that during intervals of high zircon production we have warming trends, and as zircon production diminishes, we see a shift into our cooling trends.”

equation-mantle plumes

New Equation:
Increase Charged Particles → Decreased Magnetic Field → Increase Outer Core Convection → Increase of Mantle Plumes → Increase in Earthquake and Volcanoes → Cools Mantle and Outer Core → Return of Outer Core Convection (Mitch Battros – July 2012)

One question unanswered in recent climate change debates, is what caused the fluctuations in CO2 observed in the geologic record. Other theories have suggested that geological forces such as mountain building have, at different times in the planet’s history, introduced large amounts of new material to the Earth’s surface, and weathering of that material has drawn CO2 out of the atmosphere.

warming-cooling-trends4

Using nearly 200 published studies and their own fieldwork and data, researchers created a global database to reconstruct the volcanic history of continental margins over the past 720 million years.

“We studied sedimentary basins next to former volcanic arcs, which were eroded away over hundreds of millions of years,” said co-author Brian Horton, a professor in the Jackson School’s Department of Geological Sciences. “The distinguishing part of our study is that we looked at a very long geologic record – 720 million years – through multiple warming and cooling trends.”

The cooling periods tended to correlate with the assembly of Earth’s supercontinents, which was a time of diminished continental volcanism, Horton said. The warming periods correlated with continental breakup, a time of enhanced continental volcanism.

Shifting Jet Stream and Ocean Currents Cause of Extreme Weather

Disastrous floods in the Balkans two years ago are likely linked to the temporary slowdown of portions of Earth’s jet stream. Jet Stream patterns circling the globe in the form of large oscillating waves between the Equator and the North Pole, along with shifting ocean currents have caused extreme weather events over Bosnia and Herzegovina, Serbia and Croatia that poured out record amounts of rain.

shifing jet stream and ocean currents_m

The study adds evidence that planetary wave resonance is a key mechanism for causing extreme weather event. Further, the scientists showed that extreme rainfall events are strongly increasing in certain geological areas, in this case over the Balkans.

“We were surprised to see how long the weather system that led to this recent flooding stayed over the region,” says Lisa Stadtherr from the Potsdam Institute for Climate Impact Research (PIK), lead-author of the study to be published in Science Advances. “Day after day the rain was soaking the soil until it was saturated, which lead to the flooding that reportedly caused several dozen casualties and 3.5 billion Euro of damages.”

equation 1998

Equation:
Sunspots → Solar Flares (charged particles) → Magnetic Field Shift → Shifting Ocean and Jet Stream Currents → Extreme Weather and Human Disruption (mitch battros 1998)

While the mean daily rainfall in the Balkans has increased only a little since 1950, the intensity of the strongest rainfall events rose by one third, the scientists found. In May 2014, daily rainfall amounts were locally bigger than ever before in the observed period. The frequency of such potentially devastating extremes in the Balkans, though they are still rare, doubled over the past sixty years.

convergence_zone

There was a similar situation in 1977 in Germany, resulting in the “Elbe” flooding. “This is worrisome because we’re seeing increasing extreme rainfall in many parts of the globe,” says co-author and PIK project head Dim Coumou. “The changes over the Balkan are substantially larger than those expected from simple warming of the air.” Regional temperatures rose by one degree since the middle of the past century, and the increased water holding capacity of warmer air intensifies heavy rainfall by about 7 percent per degree of warming. “Yet the observed rainfall changes in the Balkans are roughly five times that much – hence other factors must have come into play.”

This mechanism has first been put forward by PIK scientist Vladimir Petoukhov only a few years ago, opening a new branch of research; he is co-author of the present study. The scientists produced a video to explain the mechanism which might be a decisive factor for creating extreme weather events in summer in general. (actually by Mitch Battros in 1998)

equation 1998

“Our findings provide more evidence that planetary waves cause extreme weather events,” says co-author Stefan Rahmstorf, chair of PIK’s research team. “When such atmospheric waves start to oscillate this can have serious impacts for people on the ground. I am concerned this current climate cycle may be creating conditions more favorable for this kind of fluctuation.”

 

BREAKING NEWS: Ecuador 7.8 Mag. Earthquake – Death Toll Jumps to 233; More Than 1,500 Wounded

The catastrophic earthquake that destroyed buildings in Ecuador on Saturday became far more devastating Sunday, when the death toll rose to 233 — and it’s expected to rise.

sign27

Another 1,500 people were injured, said Ricardo Peñaherrera of Ecuador’s national emergency management office.

“It was the worst experience of my life,” survivor Jose Meregildo said Sunday about the tremors that violently shook his house in Guayaquil, 300 miles away from the quake’s epicenter.

ecuador-earthquake

“Everybody in my neighborhood was screaming saying it was going to be the end of the world. Residents remain on the streets for fear of aftershocks in Pedernales on April 17.

ecuador-quake04-17-2016

People make their way through debris from a collapsed building in Pedernales on Sunday, April 17. A magnitude-7.8 quake struck off Ecuador’s central coast on Saturday, April 16, flattening buildings and buckling highways. It’s the deadliest quake to strike the South

The magnitude-7.8 earthquake hit Saturday night as it buckled homes and knocked out power in Guayaquil, Ecuador’s most populous city, authorities said. Emergency officials recovered one body from the scene of a bridge collapse there.

ecuador-quake-04

“Many highways are in bad shape, especially in the mountainous area because it has been raining recently due to (the) El Niño weather phenomenon.”

Vice President Jorge Glas had said earlier the death toll is expected to rise.

A state of emergency is in effect for six provinces — Guayas, Manabi, Santo Domingo, Los Rios, Esmeraldas and Galapagos. Authorities urged those who left their homes in coastal areas to return after a tsunami alert was lifted.

During his Sunday prayer, Pope Francis asked for those present to pray for the people affected by the earthquakes in Ecuador and Japan.

“Last night a violent earthquake hit Ecuador, causing numerous victims and great damages,” Francis said. “Let’s pray for those populations, and for those of Japan, where as well there has been some earthquakes in the last days. The help of God and of the brothers give them strength and support.”

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Volcanologists Discover How Magma Bubbles Accumulate

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In 1816, summer failed to make an appearance in central Europe and people were starving. Just a year earlier, the Tambora volcano had erupted in Indonesia, spewing huge amounts of ash and sulphur into the atmosphere. As these particles partly blocked sunlight, cooling the climate, it had a serious impact on the land and the people, even in Switzerland.

magma bubbles

Since then, volcanologists have developed more precise ideas of why super-volcanoes such as Tambora are not only highly explosive but also why they release so much sulphur into the atmosphere.

Gas bubbles tend to accumulate in the upper layers of magma reservoirs, which are only a few kilometers beneath the earth’s surface, building up pressure that can then be abruptly liberated by eruption. These bubbles mainly contain water vapor but also sulphur.

“Such volcanic eruptions can be extremely powerful and spew an enormous amount of ash and sulphur to the surface,” says Andrea Parmigiani, a post-doc in the Institute of Geochemistry and Petrology at ETH Zurich. “We’ve known for some time that gas bubbles play a major role in such events, but we had only been able to speculate on how they accumulate in magma reservoirs.”

Together with other scientists from ETH Zurich and Georgia Institute of Technology (Georgia Tech), the researchers studied the behavior of bubbles with a computer model.

The scientists used theoretical calculations and laboratory experiments to examine in particular how bubbles in crystal-rich and crystal-poor layers of magma reservoirs move buoyantly upward. In many volcanic systems, the magma reservoir consists mainly of two zones: an upper layer consisting of viscous melt with almost no crystals, and a lower layer rich in crystals, but still containing pore space.

When Andrea Parmigiani, Christian Huber and Olivier Bachmann started this project, they thought that the bubbles, as they moved upwards through crystal-rich areas of the magma reservoirs, would dramatically slow down, while they would go faster in the crystal-poor zones.

“Instead, we found that, under volatile-rich conditions, they would ascend much faster in the crystal-rich zones, and accumulate in the melt-rich portions above” says Parmigiani.

Parmigiani explains this as follows: when the proportion of bubbles in the pore space of the crystal-rich layers increases, small individual bubbles coalesce into finger-like channels, displacing the existing highly viscous melt. These finger-like channels allow for a higher vertical gas velocity. The bubbles, however, have to fill at least 10 to 15 % of the pore space.

“If the vapor phase cannot form these channels, individual bubbles are mechanically trapped,” says the earth scientist. As these finger-like channels reach the boundary of the crystal-poor melt, individual, more spherical bubbles detach, and continue their ascent towards the surface. However, the more bubble, the more reduce their migration velocity is.

This is because each bubble creates a return flow of viscous melt around it. When an adjacent bubble feels this return flow, it is slowed down. This process was demonstrated in a laboratory experiment conducted by Parmigiani’s colleagues Salah Faroughi and Christian Huber at Georgia Tech, using water bubbles in a viscous silicone solution.

“Through this mechanism, a large number of gas bubbles can accumulate in the crystal-poor melt under the roof of the magma reservoir. This eventually leads to over-pressurization of the reservoir,” says lead author Parmigiani. And because the bubbles also contain sulphur, this also accumulates, explaining why such a volcano might emit more sulphur than expected based on its composition.

What this means for the explosively of a given volcano is still unclear. “This study focuses primarily on understanding the basic principles of gas flow in magma reservoirs; a direct application to prediction of volcanic behavior remains a question for the future,” says the researcher, adding that existing computer models do not depict the entire magma reservoir, but only a tiny part of it: roughly a square of a few cubic centimeter with a clear boundary between the crystal-poor and crystal-rich layers.

To calculate this small volume, Parmigiani used high-performance computers such as the Euler Cluster at ETH Zurich and a supercomputer at the Swiss National Supercomputing Centre in Lugano.

For the software, the researcher had access to the open-source library Palabos, which he continues to develop in collaboration with researchers from University of Geneva. “This software is particularly suitable for this type of simulation,” says the physicist.