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Throughout Earth’s long geologic history, the magnetic pole has not remained stable. For reasons that are still little understood, the Earth’s magnetic field can suddenly – and without warning – weaken, start to shift around, and even completely reverse direction.

Credit: Shutterstock

Records indicate that over the last 160 million years, the magnetic pole has reversed its polarity at least several hundred times. Called a “geomagnetic field reversal,” this has resulted in the poles swapping positions, with magnetic north becoming magnetic south, and vice versa. The magnetic pole has also undergone what are called “excursions.” During an excursion event, the earth’s magnetic field weakens and begins to drift but does not reverse itself. The field re-strengthens and the poles finally return to their initial position.

UC Santa Cruz geology professor Robert Coe will be presenting his paper, “What We Know and Don’t Know about Reversals” during the upcoming American Geophysical Union (AGU) meeting in Washington, D.C. this December.

Coe is an emeritus professor of geophysics, and has had a long and distinguished career. He has received numerous awards and recognition for his many research accomplishments. He received his Ph.D. at the University of California, Berkeley, and did postgraduate work in Australia before returning to the States where he joined the UC Santa Cruz faculty in 1968. He has made significant contributions in a number of areas, including volcanology, geochemistry, and tectonics. In the 1970s, he developed a method of more accurately measuring the intensity of the magnetic field in rocks – a method that bears his name. Perhaps his most significant contribution, however, has been in paleomagnetism, where he has been a pioneer in the study of magnetic field reversals.

“The Earth’s magnetic field is restless,” said Coe in a recent interview.

Evidence for this restlessness first came to light in the early twentieth century when geologists recognized that certain rocks exhibited magnetism that was different in orientation from the Earth’s then current magnetic field. While given little consideration at the time, geologists eventually acknowledged the significance of this observation and became interested in investigating the phenomenon. A number of influential papers published in the 1960s – including a number of papers authored by Coe – shed considerable light on the process by identifying polarity transitions in both lava flows and sediments.

The process by which rocks get magnetized occurs when they are formed, Coe explained. Scientists know much more about how volcanic rocks become magnetized than they do about sedimentary rocks. As igneous rocks cool, for example, they become magnetized in the direction of the field prevailing at the moment. This process may take a few days or a few years and provides a “snapshot” of the Earth’s magnetic field, he added. Consequently, by studying many different rocks formed during different geologic periods, researchers can create a record of the Earth’s history of magnetic wanderings.

One of the best records of the earth’s magnetic reversals comes from Steens Mountain in southeastern Oregon. Here, a series of overlapping Miocene-age basaltic lava flows record a complex history of several thousand years of Earth’s geomagnetic history. Significantly, the Steens Mountain record bears evidence of a complete magnetic reversal that occurred at an extraordinarily rapid pace (between 3 and 8 degrees per day) some15.5 million years ago.

Unfortunately, magnetic reversals can be far more complex than even the best, most detailed paleomagnetic record on hand. Volcanic records are limited by the “discontinuous and episodic nature of volcanic eruptions,” Coe said. To better understand Earth’s geomagnetic history, Coe emphasized, we need to have excellent records not only from volcanic contexts but also from sedimentary data.

Highly detailed deep-sea cores recently obtained during drilling operations in the North Atlantic might provide the lynchpin. These were obtained from a vertical section of the ocean floor and provide a continuous sequence of magnetized strata.

“The North Atlantic records give one hope,” Coe said.

Today, much has been learned about reversals in the Earth’s magnetic field.

It is now known, for example, that magnetic reversals happen much more frequently than previously surmised, and that they can often occur at incredibly rapid clips. It is also known that the last complete reversal, which occurred 770,000 years ago, occurred over a span of less than 100 years.

Much more, however, is still to be learned.

Most importantly, geologists continue to debate the cause of these reversals.

“A magnetic reversal certainly has a large random or chaotic aspect,” Coe said. “And it’s active over many time scales.”

Although a number of theories have been posited, the prevailing explanation suggests that reversals are ultimately tied to the Earth’s convective motion.

“The Earth’s magnetic field comes from a dynamo-like action arising from the motion of the metallic fluids in the outer core,” he said.

Scientists have also debated whether a reversal can cause major hazards, especially to technology. Some have argued that a reversal would cause the failure of the worldwide electronic and communication systems. The question, however, is controversial and remains unanswered.

Author: Tom Garlinghouse | Source: University of California - Santa Cruz [December 11, 2018]

Seventy percent of the current infrastructure in the Arctic has a high potential to be affected by thawing permafrost in the next 30 years. Even meeting the climate change targets of the Paris Agreement will not substantially reduce those projected impacts, according to a new study published in Nature Communications.

UAF researcher Vladimir Romanovsky poses near Fairbanks, Alaska in a place where permafrost has thawed, causing a surface disruption [Credit: University of Alaska Fairbanks]

"Much more needs to be done to prepare Alaska and Alaskans for the adverse consequences of coming changes in permafrost and climate," said Vladimir Romanovsky, a scientist with the University of Alaska Fairbanks Geophysical Institute who has been monitoring permafrost across Alaska for 25 years.

Permafrost is ground that is frozen year-round for a minimum of two years. When it thaws, it can change from solid earth into mud. In many cases, the ground will slump, leading to destructive failure in any structures erected there.

"These observations have led me to believe that the global warming is not a 'fake' but the reality," Romanovsky said. "And here, in Alaska, we are dealing already and will be dealing even more in the near future with this reality."

Romanovsky is one of the study's authors, along with researchers from Finland, Norway, Russia and Michigan. The research is the first to explicitly show the amount of fundamental infrastructure across the Northern Hemisphere that is at risk of structural failure from permafrost thaw caused by climate change.

The paper reports that by 2050, about three-quarters of the population now living on permafrost, about 3.6 million people, will be affected by damage to infrastructure from permafrost thaw. In Alaska, about 340 miles of the trans-Alaska oil pipeline traverses ground where near-surface permafrost may thaw by 2050.

"The results show that most fundamental Arctic infrastructure will be at risk, even if the Paris Agreement target is achieved," the authors write. However, after 2050, attaining the Paris Agreement goals would make a clear difference in potential damage to infrastructure.

The authors looked at measurements of ground temperature, annual thaw depth and other data to make their projections. They note that because of the uncertainties, the amount of infrastructure at risk from permafrost thaw is probably not much smaller than their estimate, but could be substantially larger.

Damage to industrial facilities such as pipelines could lead to major ecosystem disruption if it results in spills. Energy supplies, national security and general economic activity could be adversely affected as well, the authors write. The Yamal-Nenets region in northwestern Siberia is the source of more than one-third of the European Union's pipeline imports of natural gas, for example.

Many parts of the Arctic's infrastructure have relatively short lifespans. Planners and engineers need to know in detail where permafrost is most likely to thaw as they plan for replacements, upgrades and maintenance. This study mapped such areas at a resolution of 0.6 miles, allowing them to target mitigation where it is most needed.

Source: University of Alaska Fairbanks [December 11, 2018]

About 2.6 million years ago, an oddly bright light arrived in the prehistoric sky and lingered there for weeks or months. It was a supernova some 150 light years away from Earth. Within a few hundred years, long after the strange light in the sky had dwindled, a tsunami of cosmic energy from that same shattering star explosion could have reached our planet and pummeled the atmosphere, touching off climate change and triggering mass extinctions of large ocean animals, including a shark species that was the size of a school bus.

A nearby supernova remnant [Credit: NASA]

The effects of such a supernova -- and possibly more than one -- on large ocean life are detailed in a paper just published in Astrobiology.

"I've been doing research like this for about 15 years, and always in the past it's been based on what we know generally about the universe -- that these supernovae should have affected Earth at some time or another," said lead author Adrian Melott, professor emeritus of physics & astronomy at the University of Kansas. "This time, it's different. We have evidence of nearby events at a specific time. We know about how far away they were, so we can actually compute how that would have affected the Earth and compare it to what we know about what happened at that time -- it's much more specific."

Melott said recent papers revealing ancient seabed deposits of iron-60 isotopes provided the "slam-dunk" evidence of the timing and distance of supernovae.

"As far back as the mid-1990s, people said, 'Hey, look for iron-60. It's a telltale because there's no other way for it to get to Earth but from a supernova.' Because iron-60 is radioactive, if it was formed with the Earth it would be long gone by now. So, it had to have been rained down on us. There's some debate about whether there was only one supernova really nearby or a whole chain of them. I kind of favor a combo of the two -- a big chain with one that was unusually powerful and close. If you look at iron-60 residue, there's a huge spike 2.6 million years ago, but there's excess scattered clear back 10 million years."

Melott's co-authors were Franciole Marinho of Universidade Federal de Sao Carlos in Brazil and Laura Paulucci of Universidade Federal do ABC, also in Brazil.

According to the team, other evidence for a series of supernovae is found in the very architecture of the local universe.

"We have the Local Bubble in the interstellar medium," Melott said. "We're right on its edge. It's a giant region about 300 light years long. It's basically very hot, very low-density gas -- nearly all the gas clouds have been swept out of it. The best way to manufacture a bubble like that is a whole bunch of supernovae blows it bigger and bigger, and that seems to fit well with idea of a chain. When we do calculations, they're based on the idea that one supernova that goes off, and its energy sweeps by Earth, and it's over. But with the Local Bubble, the cosmic rays kind of bounce off the sides, and the cosmic-ray bath would last 10,000 to 100,000 years. This way, you could imagine a whole series of these things feeding more and more cosmic rays into the Local Bubble and giving us cosmic rays for millions of years."

Muons showering Earth may have spelled curtains for Megalodon, a school-bus-sized shark, 2.6 million years ago [Credit: Karen Carr]

Whether or not there was one supernova or a series of them, the supernova energy that spread layers of iron-60 all over the world also caused penetrating particles called muons to shower Earth, causing cancers and mutations -- especially to larger animals.

"The best description of a muon would be a very heavy electron - but a muon is a couple hundred times more massive than an electron," Melott said. "They're very penetrating. Even normally, there are lots of them passing through us. Nearly all of them pass through harmlessly, yet about one-fifth of our radiation dose comes by muons. But when this wave of cosmic rays hits, multiply those muons by a few hundred. Only a small faction of them will interact in any way, but when the number is so large and their energy so high, you get increased mutations and cancer -- these would be the main biological effects. We estimated the cancer rate would go up about 50 percent for something the size of a human -- and the bigger you are, the worse it is. For an elephant or a whale, the radiation dose goes way up."

A supernova 2.6 million years ago may be related to a marine megafaunal extinction at the Pliocene-Pleistocene boundary where 36 percent of the genera were estimated to become extinct. The extinction was concentrated in coastal waters, where larger organisms would catch a greater radiation dose from the muons.

According to the authors of the new paper, damage from muons would extend down hundreds of yards into ocean waters, becoming less severe at greater depths: "High energy muons can reach deeper in the oceans being the more relevant agent of biological damage as depth increases," they write.

Indeed, a famously large and fierce marine animal inhabiting shallower waters may have been doomed by the supernova radiation.

"One of the extinctions that happened 2.6 million years ago was Megalodon," Melott said. "Imagine the Great White Shark in 'Jaws,' which was enormous -- and that's Megalodon, but it was about the size of a school bus. They just disappeared about that time. So, we can speculate it might have something to do with the muons. Basically, the bigger the creature is the bigger the increase in radiation would have been."

The KU researcher said the evidence of a supernova, or series of them, is "another puzzle piece" to clarify the possible reasons for the Pliocene-Pleistocene boundary extinction.

"There really hasn't been any good explanation for the marine megafaunal extinction," Melott said. "This could be one. It's this paradigm change -- we know something happened and when it happened, so for the first time we can really dig in and look for things in a definite way. We now can get really definite about what the effects of radiation would be in a way that wasn't possible before."

Source: University of Kansas [December 11, 2018]

Our future on Earth may also be our past. In a study published in the Proceedings of the National Academy of Sciences, researchers show that humans are reversing a long-term cooling trend tracing back at least 50 million years. And it's taken just two centuries.

Epihippus gracilis, one of the many early horses found in the Hancock Mammal Quarry in Oregon, depicted around 30 million years ago. Their ancestors would have gotten their start in the Eocene [Credit: National Park Services]

By 2030, Earth's climate is expected to resemble that of the mid-Pliocene, going back more than 3 million years in geologic time. Without reductions in our greenhouse gas emissions, our climates by 2150 could compare to the warm and mostly ice-free Eocene, an epoch that characterized the globe 50 million years ago.

"If we think about the future in terms of the past, where we are going is uncharted territory for human society," says the study's lead author, Kevin Burke, who conducted the work while a graduate student in the lab of paleoecologist John "Jack" Williams, professor of geography at the University of Wisconsin-Madison. "We are moving toward very dramatic changes over an extremely rapid time frame, reversing a planetary cooling trend in a matter of centuries."

All of the species on Earth today had an ancestor that survived the Eocene and the Pliocene, but whether humans and the flora and fauna we are familiar with can adapt to these rapid changes remains to be seen. The accelerated rate of change appears to be faster than anything life on the planet has experienced before.

The new study builds upon work Williams and colleagues first published in 2007, which compared future climate projections to historical climate data from the early 20th century. The new study relies on extensive data about climate conditions to probe much deeper in Earth's geologic past and expand those comparisons.

"We can use the past as a yardstick to understand the future, which is so different from anything we have experienced in our lifetimes," says Williams. "People have a hard time projecting what the world will be like five or 10 years from now. This is a tool for predicting that -- how we head down those paths, and using deep geologic analogs from Earth's history to think about changes in time."

During the Eocene, Earth's continents were packed more closely together and global temperatures averaged 23.4 degrees Fahrenheit (13 degrees Celsius) warmer than they are today. Dinosaurs had recently gone extinct and the first mammals, like ancestral whales and horses, were spreading across the globe. The Arctic was occupied by swampy forests like those found today in the southern U.S.

Future climate analogs for the years 2020, 2050, 2100 and 2200 according to three well-established models. If greenhouse gas emissions are not curbed, the study says, the climate will continue to warm until it begins to resemble the Eocene in 2100 [Credit: Burke et al. 2018]

In the Pliocene, North and South America joined tectonically, the climate was arid, land bridges allowed animals to spread across continents and the Himalayas formed. Temperatures were between 3.2 and 6.5 degrees Fahrenheit (1.8 to 3.6 degrees Celsius) warmer than they are today.

For the study, Burke and Williams -- along with colleagues at the University of Bristol, Columbia University, University of Leeds, NASA Goddard Institute for Space Studies and the National Center for Atmospheric Research -- examined the similarities between future climate projections as set forth by the Intergovernmental Panel on Climate Change Fifth Assessment Report and several periods of geologic history.

These included the Early Eocene, the mid-Pliocene, the Last Interglacial (129 to 116 thousand years ago), the mid-Holocene (6,000 years ago), the pre-industrial era (before A.D. 1850) and the early 20th century.

They used Representative Concentration Pathway 8.5 (RCP8.5), which represents a future climate scenario in which we do not mitigate greenhouse gas emissions, and RCP4.5, a scenario in which we moderately reduce greenhouse gas emissions, and climate simulations using three different but well-established models: the Hadley Centre Coupled Model version 3, the Goddard Institute for Space Studies ModelE2-R and the Community Climate System Model.

While not without their flaws, each of these models represents the best available data and state-of-the-art techniques.

Under both scenarios and across each model, compared to previous eras, the Earth's climate most closely resembled the mid-Pliocene by 2030 (under RCP8.5) or 2040 (under RCP4.5). Under the greenhouse gas stabilization scenario of RCP4.5, the climate then stabilizes at mid-Pliocene-like conditions, but under the higher greenhouse gas emissions of RCP8.5, the climate continues to warm until it begins to resemble the Eocene in 2100, achieving Eocene-like conditions more broadly by 2150.

The models showed these deep-geological climates emerging first from the center of continents and then expanding outward over time. Temperatures rise, precipitation increases, ice caps melt and climates become temperate near the Earth's poles.

"Madison (Wisconsin) warms up more than Seattle (Washington) does, even though they're at the same latitude," Williams explains. "When you read that the world is expected to warm by 3 degrees Celsius this century, in Madison we should expect to roughly double the global average."


The study also showed that under RCP8.5, "novel" climates emerge across nearly 9 percent of the planet. These are conditions that do not have known geologic or historical precedent and they concentrate in eastern and southeastern Asia, northern Australia and the coastal Americas.

"Based on observational data, we are tracking on the high end of the emissions scenarios, but it's too soon to tell," says Burke. "We may be somewhere between RCP4.5 and RCP8.5, though if we increase our climate mitigation efforts -- like switching to renewable energy -- we could find ourselves closer to the low end."

About a decade ago, Swedish scientist Johan Rockström and colleagues introduced the idea of "safe operating space," referring to the climate conditions under which modern agricultural societies developed. By comparing to the deep past, Williams and Burke say, we are able to better understand the planetary boundaries and thresholds that delineate this space.

"The further we move from the Holocene, the greater the potential that we move out of safe operating space," says Williams, a faculty affiliate with the UW-Madison Nelson Institute Center for Climatic Research. "In the roughly 20 to 25 years I have been working in the field, we have gone from expecting climate change to happen, to detecting the effects, and now, we are seeing that it's causing harm. People are dying, property is being damaged, we're seeing intensified fires and intensified storms that can be attributed to climate change. There is more energy in the climate system, leading to more intense events."

In their paper, the researchers try to strike a balance between alarm and optimism. On the one hand, Earth is headed into the unknown in our children's and grandchildren's lifetimes. On the other, life has long proven to be resilient. And, Williams says, in many places we are moving away from fossil fuels toward more sustainable and carbon-free energy sources. But more needs to be done.

"We've seen big things happen in Earth's history -- new species evolved, life persists and species survive. But many species will be lost, and we live on this planet," says Williams. "These are things to be concerned about, so this work points us to how we can use our history and Earth's history to understand changes today and how we can best adapt."

Author: Kelly April Tyrrell | Source: University of Wisconsin-Madison [December 10, 2018]

The largest extinction in Earth's history marked the end of the Permian period, some 252 million years ago. Long before dinosaurs, our planet was populated with plants and animals that were mostly obliterated after a series of massive volcanic eruptions in Siberia.

This illustration shows the percentage of marine animals that went extinct at the end of the Permian era by latitude, from the model (black line) and from the fossil record (blue dots). A greater percentage of marine animals survived in the tropics than at the poles. The color of the water shows the temperature change, with red being most severe warming and yellow less warming. At the top is the supercontinent Pangaea, with massive volcanic eruptions emitting carbon dioxide. The images below the line represent some of the 96 percent of marine species that died during the event. Includes  fossil drawings by Ernst Haeckel/Wikimedia; Blue crab photo by Wendy Kaveney/Flickr; Atlantic cod photo by Hans-Petter Fjeld/Wikimedia; Chambered nautilus photo by ©2010 John White/CalPhotos [Credit: Justin Penn and Curtis Deutsch/University of Washington]

Fossils in ancient seafloor rocks display a thriving and diverse marine ecosystem, then a swath of corpses. Some 96 percent of marine species were wiped out during the "Great Dying," followed by millions of years when life had to multiply and diversify once more.

What has been debated until now is exactly what made the oceans inhospitable to life - the high acidity of the water, metal and sulfide poisoning, a complete lack of oxygen, or simply higher temperatures.

New research from the University of Washington and Stanford University combines models of ocean conditions and animal metabolism with published lab data and paleoceanographic records to show that the Permian mass extinction in the oceans was caused by global warming that left animals unable to breathe. As temperatures rose and the metabolism of marine animals sped up, the warmer waters could not hold enough oxygen for them to survive.

"This is the first time that we have made a mechanistic prediction about what caused the extinction that can be directly tested with the fossil record, which then allows us to make predictions about the causes of extinction in the future," said first author Justin Penn, a UW doctoral student in oceanography.

This fossilized spiraling shark tooth is from the Helicoprion, an unusual shark that lived during the Permian. The tooth whorl was located inside the shark’s lower jaw. The fossil is on display at the Idaho Museum of Natural History [Credit: James St. John/Flickr]

Researchers ran a climate model with Earth's configuration during the Permian, when the land masses were combined in the supercontinent of Pangaea. Before ongoing volcanic eruptions in Siberia created a greenhouse-gas planet, oceans had temperatures and oxygen levels similar to today's. The researchers then raised greenhouse gases in the model to the level required to make tropical ocean temperatures at the surface some 10 degrees Celsius (20 degrees Fahrenheit) higher, matching conditions at that time.

The model reproduces the resulting dramatic changes in the oceans. Oceans lost about 80 percent of their oxygen. About half the oceans' seafloor, mostly at deeper depths, became completely oxygen-free.

To analyze the effects on marine species, the researchers considered the varying oxygen and temperature sensitivities of 61 modern marine species -- including crustaceans, fish, shellfish, corals and sharks -- using published lab measurements. The tolerance of modern animals to high temperature and low oxygen is expected to be similar to Permian animals because they had evolved under similar environmental conditions. The researchers then combined the species' traits with the paleoclimate simulations to predict the geography of the extinction.

"Very few marine organisms stayed in the same habitats they were living in -- it was either flee or perish," said second author Curtis Deutsch, a UW associate professor of oceanography.

A fossil from Morocco of a Diademaproetus, one of the trilobites that were plentiful in the world’s oceans but went extinct at the end of the Permian [Credit: Géry Parent/Flickr]

The model shows the hardest hit were organisms most sensitive to oxygen found far from the tropics. Many species that lived in the tropics also went extinct in the model, but it predicts that high-latitude species, especially those with high oxygen demands, were nearly completely wiped out.

To test this prediction, co-authors Jonathan Payne and Erik Sperling at Stanford analyzed late-Permian fossil distributions from the Paleoceanography Database, a virtual archive of published fossil collections. The fossil record shows where species were before the extinction, and which were wiped out completely or restricted to a fraction of their former habitat.

The fossil record confirms that species far from the equator suffered most during the event.

"The signature of that kill mechanism, climate warming and oxygen loss, is this geographic pattern that's predicted by the model and then discovered in the fossils," Penn said. "The agreement between the two indicates this mechanism of climate warming and oxygen loss was a primary cause of the extinction."

A fossil of a Paramblypterus, a species of fish that went extinct during the Permian. This fossil is on display at the State Museum of Natural History in Karlsruhe, Germany [Credit: H. Zell/WikiCommons]

The study builds on previous work led by Deutsch showing that as oceans warm, marine animals' metabolism speeds up, meaning they require more oxygen, while warmer water holds less. That earlier study shows how warmer oceans push animals away from the tropics.

The new study combines the changing ocean conditions with various animals' metabolic needs at different temperatures. Results show that the most severe effects of oxygen deprivation are for species living near the poles.

"Since tropical organisms' metabolisms were already adapted to fairly warm, lower-oxygen conditions, they could move away from the tropics and find the same conditions somewhere else," Deutsch said. "But if an organism was adapted for a cold, oxygen-rich environment, then those conditions ceased to exist in the shallow oceans."

The so-called "dead zones" that are completely devoid of oxygen were mostly below depths where species were living, and played a smaller role in the survival rates. "At the end of the day, it turned out that the size of the dead zones really doesn't seem to be the key thing for the extinction," Deutsch said. "We often think about anoxia, the complete lack of oxygen, as the condition you need to get widespread uninhabitability. But when you look at the tolerance for low oxygen, most organisms can be excluded from seawater at oxygen levels that aren't anywhere close to anoxic."

This roughly 1.5-foot slab of rock from southern China shows the Permian-Triassic boundary. The bottom section is pre-extinction limestone. The upper section is microbial limestone deposited after the extinction [Credit: Jonathan Payne/Stanford University]

Warming leading to insufficient oxygen explains more than half of the marine diversity losses. The authors say that other changes, such as acidification or shifts in the productivity of photosynthetic organisms, likely acted as additional causes.

The situation in the late Permian -- increasing greenhouse gases in the atmosphere that create warmer temperatures on Earth -- is similar to today.

"Under a business-as-usual emissions scenarios, by 2100 warming in the upper ocean will have approached 20 percent of warming in the late Permian, and by the year 2300 it will reach between 35 and 50 percent," Penn said. "This study highlights the potential for a mass extinction arising from a similar mechanism under anthropogenic climate change."

The study is published in the journal Science.

Author: Hannah Hickey | Source: University of Washington [December 06, 2018]

Scientists long believed that the lower mantle was composed of Bridgmanite (Mg,Fe)SiO₃ and magnesiowüstite (Mg,Fe)O, in which Fe2+ dwells. This view changed when experiments showed that Fe²⁺ simply can't exist at the pressure and temperature of the lower mantle. What is present is Fe³⁺. The two phases (Mg,Fe)SiO₃ and (Mg,Fe)O both shed Fe²⁺ and, in turn, MgSiO₃ and MgO remain. However, what mineral hosts Fe³⁺ had remained a secret.

Maohokite [Credit: CHEN Ming]

Now scientists have a possible answer: Maohokite, a newly discovered high-pressure mineral. It may be what composes the Earth's lower mantle along with Bridgmanite MgSiO₃ and magnesiowüstite MgO. The study reporting this new mineral was published in Meteoritics & Planetary Science.

Maohokite was discovered by CHEN Ming's team from the Guangzhou Institute of Geochemistry of the Chinese Academy of Sciences and SHU Jinfu from the Center for High Pressure Science and Technology Advanced Research. The mineral was named after Hokwang Mao, in honor of his great contribution to high-pressure research.

The mineral and its name have been approved by the Commission on New Minerals, Nomenclature and Classification of the International Mineralogical Association under the designator IMA 2017-047.

Natural minerals can be divided into two types: low-pressure minerals and high-pressure minerals, depending on their formation pressures. The pressure and temperature required for the formation of high-pressure minerals can only be provided by the environment of the mantle or the hypervelocity collision between celestial bodies.

Maohokite is the second case. It was found in shock-metamorphosed rocks from the Xiuyan impact crater in China.

This high-pressure mineral was formed from the decomposition of ferromagnesian carbonate via a self-oxidation-reduction reaction at a temperature >900 °C and impact pressure >25 GPa (a pressure range found at depths more than 670km below Earth's surface). In this reaction,  Fe²⁺ oxidizes into Fe³⁺ and then later combines with  Mg²⁺ to form maohokite, thus making it a possible important constituent of the lower mantle.

Maohokite, with a composition of MgFe₂O₄, has an orthorhombic CaFe₂O₄-type structure. The existing mineralogical model of the Earth's mantle shows that the ferromagnesian lower mantle is mainly composed of Bridgmanite (Mg,Fe)SiO₃ and magnesiowüstite (Mg,Fe)O. Therefore, the fact that Maohokite contains Mg and Fe, two major components of the lower mantle, only makes the case stronger that Maokohite is a key mineral in the lower mantle.

Source: Chinese Academy of Sciences [December 05, 2018]

Surface melting across Greenland's mile-thick ice sheet began increasing in the mid-19th century and then ramped up dramatically during the 20th and early 21st centuries, showing no signs of abating, according to new research published in the journal Nature. The study provides new evidence of the impacts of climate change on Arctic melting and global sea level rise.

Large rivers form on the surface of Greenland each summer, rapidly moving meltwater from the ice sheet to the ocean [Credit: Sarah Das, Woods Hole Oceanographic Institution]

"Melting of the Greenland Ice Sheet has gone into overdrive. As a result, Greenland melt is adding to sea level more than any time during the last three and a half centuries, if not thousands of years," said Luke Trusel, a glaciologist at Rowan University's School of Earth & Environment and former post-doctoral scholar at Woods Hole Oceanographic Institution, and lead author of the study. "And increasing melt began around the same time as we started altering the atmosphere in the mid-1800s."

"From a historical perspective, today's melt rates are off the charts, and this study provides the evidence to prove this" said Sarah Das, a glaciologist at Woods Hole Oceanographic Institution (WHOI) and co-author of the study. "We found a fifty percent increase in total ice sheet meltwater runoff versus the start of the industrial era, and a thirty percent increase since the 20th century alone."

Ice loss from Greenland is one of the key drivers of global sea level rise. Icebergs calving into the ocean from the edge of glaciers represent one component of water re-entering the ocean and raising sea levels. But more than half of the ice-sheet water entering the ocean comes from runoff from melted snow and glacial ice atop the ice sheet. The study suggests that if Greenland ice sheet melting continues at "unprecedented rates" -- which the researchers attribute to warmer summers -- it could accelerate the already fast pace of sea level rise.

"Rather than increasing steadily as climate warms, Greenland will melt increasingly more and more for every degree of warming. The melting and sea level rise we've observed already will be dwarfed by what may be expected in the future as climate continues to warm," said Trusel.


To determine how intensely Greenland ice has melted in past centuries, the research team used a drill the size of a traffic light pole to extract ice cores from the ice sheet itself and an adjacent coastal ice cap, at sites more than 6,000 feet above sea level. The scientists drilled at these elevations to ensure the cores would contain records of past melt intensity, allowing them to extend their records back into the 17th century. During warm summer days in Greenland, melting occurs across much of the ice sheet surface. At lower elevations, where melting is the most intense, meltwater runs off the ice sheet and contributes to sea level rise, but no record of the melt remains. At higher elevations, however, the summer meltwater quickly refreezes from contact with the below-freezing snowpack sitting underneath. This prevents it from escaping the ice sheet in the form of runoff. Instead, it forms distinct icy bands that stack up in layers of densely packed ice over time.

The core samples were brought back to ice core labs at the U.S. National Science Foundation Ice Core Facility in Denver, Colo., WHOI in Woods Hole, Mass., Wheaton College in Norton, Mass., and the Desert Research Institute in Reno, Nev. where the scientists measured physical and chemical properties along the cores to determine the thickness and age of the melt layers. Dark bands running horizontally across the cores, like ticks on a ruler, enabled the scientists to visually chronicle the strength of melting at the surface from year to year. Thicker melt layers represented years of higher melting, while thinner sections indicated years with less melting.

Combining results from multiple ice cores with observations of melting from satellites and sophisticated climate models, the scientists were able to show that the thickness of the annual melt layers they observed clearly tracked not only how much melting was occurring at the coring sites, but also much more broadly across Greenland. This breakthrough allowed the team to reconstruct meltwater runoff at the lower-elevation edges of the ice sheet -- the areas that contribute to sea level rise.

Study lead author and WHOI post-doc Dr. Luke Trusel (now at Rowan University) takes field measurements of a section of ice core from Greenland before packing it for transport home [Credit: Sarah Das, Woods Hole Oceanographic Institution]

Ice core records provide critical historical context because satellite measurements -- which scientists rely on today to understand melting rates in response to changing climate -- have only been around since the late 1970s, said Matt Osman, a graduate student in the MIT-WHOI Joint Program and co-author of the study.

"We have had a sense that there's been a great deal of melting in recent decades, but we previously had no basis for comparison with melt rates going further back in time," he said. "By sampling ice, we were able to extend the satellite data by a factor of 10 and get a clearer picture of just how extremely unusual melting has been in recent decades compared to the past."

Trusel said the new research provides evidence that the rapid melting observed in recent decades is highly unusual when put into a historical context.

"To be able to answer what might happen to Greenland next, we need to understand how Greenland has already responded to climate change," he said. "What our ice cores show is that Greenland is now at a state where it's much more sensitive to further increases in temperature than it was even 50 years ago."

One noteworthy aspect of the findings, Das said, was how little additional warming it now takes to cause huge spikes in ice sheet melting.

"Even a very small change in temperature caused an exponential increase in melting in recent years," she said. "So the ice sheet's response to human-caused warming has been non-linear." Trusel concluded, "Warming means more today than it did in the past."

Additional co-authors are: Matthew B. Osman, MIT/WHOI Joint Program in Oceanography; Matthew J. Evans, Wheaton College; Ben E. Smith, University of Washington; Xavier Fettweis, University of Leige; Joseph R. McConnell, Desert Research Institute; and Brice P. Y. Noël and and Michiel R. van den Broeke Utrecht University.

This research was funded by the US National Science Foundation, institutional support from Rowan University and Woods Hole Oceanographic Institution, the US Department of Defense, the Netherlands Organization for Scientific Research, the Netherlands Earth System Science Center, and the Belgian National Fund for Scientific Research.

Source: Woods Hole Oceanographic Institution [December 05, 2018]

Volcanoes are not fed by molten magma formed in large chambers finds a new study, overturning classic ideas about volcanic eruptions.

Volcano Fuego in Antigua, Guatemala [Credit: fboudrias/Shutterstock]

Instead, the study suggests that volcanoes are fed by so-called 'mush reservoirs' - areas of mostly solid crystals with magma in the small spaces between the crystals.

Our understanding of volcanic processes, including those leading to the largest eruptions, has been based on magma being stored in liquid-filled 'magma' chambers - large, underground caves full of liquid magma. However, these have never been observed.

The new study, by researchers at Imperial College London and the University of Bristol and published in Nature, suggests the fundamental assumption of a magma chamber needs a re-think.

Lead author Professor Matthew Jackson, from the Department of Earth Sciences and Engineering at Imperial, said: "We now need to look again at how and why eruptions occur from mush reservoirs. We can apply our findings to understanding volcanic eruptions with implications for public safety and also to understand the formation of metal ore deposits associated with volcanic systems."

In order to erupt, volcanoes need a source of magma - melted, liquid rock - containing relatively few solid crystals. Traditionally, this magma was thought to be formed and stored in a large underground cave, called a magma chamber.

The traditional picture of a magma chamber needs a re-think [Credit: Artur Balytskyi/Shutterstock]

Recent studies of magma chemistry have challenged this view, leading to the suggestion of the mush reservoir model, where smaller pools of magma sit in the small gaps between solid crystals. However, the mush reservoir model could not explain how magmas containing relatively few crystals arise and are delivered to volcanoes in order for them to erupt at the surface.

Now, with sophisticated modelling of mush reservoirs, the research team has come up with a solution. Within the mush reservoir scenario, the magma is less dense than the crystals, causing it to rise up through the spaces between them.

As it rises, the magma reacts with the crystals, melting them and leading to local areas containing magma with relatively few crystals. It is these short-lived areas of increased magma that can lead to eruptions.

Co-author Professor Stephen Sparks, from the University of Bristol's School of Earth Sciences, said: "A major mystery about volcanoes is that they were thought to be underlain by large chambers of molten rock. Such magma chambers, however, were very difficult to find.

"The new idea developed by geologists at Imperial and Bristol is that molten rock forms within largely crystalline hot rocks, spending most of its time in little pores within the rock rather than in large magma chambers. However, the rock melt is slowly squeezed out to form pools of melt, which can then erupt or form ephemeral magma chambers."

As well as the initiation of eruptions, the new mush reservoir model can help explain other phenomena in volcanic systems, such as how the magma chemical composition evolves and how much older crystals can be erupted within younger magmas.

Author: Hayley Dunning | Source: Imperial College London [December 04, 2018]

When a population grows quickly and farms intensively, the environment often suffers. This is not only true today, but was also the case as early as Roman times. Evidence of this has been found by Eawag researchers in sediments in Lake Murten.

Reconstruction of the city of Aventicum on Lake Murten, former capital of Roman Switzerland. The picture is taken from the book “Aventicum — A Roman Capital City” by Daniel Castella et al (2015)

“We are polluting the rivers and the natural elements, and even ruining the very thing that is essential to life — the air.” These words were not spoken by nature conservationists in the 21st century but flowed from the pen of the Roman scholar Pliny the Elder. In fact ancient history researchers agree today that even in Roman times the environment was being polluted – by unfiltered wastewater, the mining of metals such as iron or lead and clear-cutting of the forests. Lake Murten did not escape these depredations, as a new Eawag investigation has shown.

For the study, the research team led by paleolimnologist Mischa Haas took a ten-meter long sediment core from the deepest part of Lake Murten, which enabled them to create a reconstruction of environmental conditions that spanned several centuries.

Removing a long sediment core requires a great deal of expertise [Credit: Franziska Baumann]

The results of the sediment-core analysis surprised the researchers: “We had not expected that signs of the Romans would be so evident in the lake sediment,” comments Mischa Haas. He is referring to the varves, clearly recognizable in the sediment core and stemming from the period in which the Romans flourished on Lake Murten. Varves are alternating dark and light sediment layers that arise when neither oxygen nor living things are found on the lake bottom.

The results can be traced back to the explosive population growth during Roman times, which led to clear-cutting of numerous forests by the Lake Murten population in order to acquire wood for burning and building and to establish fields for agriculture. The ensuing erosion of the earth washed many nutrients like phosphorous, nitrogen and iron into Lake Murten, which became eutrophied – resulting in oxygen deprivation for many fish and other organisms.

This part of the sediment core shows the section with the Roman varves. Each pair of dark and light layers represents one year [Credit: Eawag]

The researchers were not only able to prove the drastic impingement by the Romans on the ecosystem: “It is also interesting that we can see in the sediments exactly when the Roman empire began to fall apart and how the lake reacted to such social revolution,” says Mischa Haas. The lake sediments show that from about the 2nd century AD more oxygen was present in the lake depths. However, it took a good 300 years for the ecosystem to recover,” the researcher points out.

This finding also has relevance to us today also plays an important role at present, as the recovery rate of lake systems is still largely unknown – in spite of numerous renaturalisation projects and new environmental legislation. “Our study shows that human interference in an ecosystem has an effect that can last for hundreds of years,” says Mischa Haas.

The study is published in Earth and Planetary Sciences Letters.

Source: Eawag [December 01, 2018]

One of the most fundamental unexplained questions in modern science is how life began. Scientists generally believe that simple molecules present in early planetary environments were converted to more complex ones that could have helped jumpstart life by the input of energy from the environment.

Starting from hydrogen cyanide, the one-pot synthesis of cyanamide and precursors to simple sugars in water -- using  gamma rays in the presence of ammonium and chloride salts -- offers a way forward for engineering complex  mixtures that can evolve important, potentially prebiological compounds [Credit: Chemistry Select]

Scientists consider the early Earth was suffused with many kinds of energy, from the high temperatures produced by volcanoes to the ultraviolet radiation beamed down by the sun. One of the most classic studies of how organic compounds could have been made on the early Earth is the Miller-Urey experiment, which showed you electrical discharges simulating lightning can help make a variety of organic compounds, including amino acids, which are basic building blocks of all life.

Another important source of energy in planetary environments is high-energy radiation, which has various sources including radioactive decay of naturally occurring chemical elements such as uranium and potassium. Research led by Yi Ruiqin and Albert Fahrenbach from the Earth-Life Science Institute (ELSI) at Tokyo Institute of Technology, Japan, has recently shown that a variety of compounds useful for the synthesis of RNA, are produced when simple compound, combined with sodium chloride, are exposed to gamma rays.

This work importantly brings us one step closer to understanding how RNA, which is widely thought to be a candidate molecule for helping start life, could have arisen abiotically on early Earth. Due to its complexity, making RNA "from scratch" under primitive solar system conditions is no easy task. Biology is great at it, because it has evolved over billions of years to do the job with amazing efficiency.

Before life emerged, there would have been little in the environment that would have assisted in making RNA. These researchers found that sodium chloride - or common table salt - can assist in making the necessary building blocks for RNA. Sodium chloride is the chemical compound that makes the sea salty, thus it is highly likely this process could occur on primitive planets, including Earth.

The most challenging aspect of this work was figuring out that salt, specifically the chloride component, played a crucial role in these reactions. Typically, chemists ignore chloride in their reactions. When chemists conduct reactions in water, it is highly likely at least some chloride is in there anyway, though most of the time it just sits idly by as a "spectator." It often doesn't play a significant role in the reactions chemists are interested in, it's just part of the background a lot of the time.

These researchers found out though, that this was not the case in their experiments, and it took them some time to figure that out. What they eventually deduced was that the ionizing radiation they were using as the energy source to drive their reactions causes chloride to lose an electron and become what is known as a "radical". As the name suggests, the chloride is then no longer so mild-mannered and becomes much more chemically reactive. Once the chloride is activated by gamma radiation, it is free to help construct other high energy compounds which finally can help build up complex RNA molecules.

While these researchers haven't yet coaxed their reactions all the way to RNA, this work shows that there is now nothing in principle which should stop this from occurring. The question now is not so much how to make all the necessary building blocks to make RNA, but how to combine them in a "warm little pond" to make the first RNA polymers. One of the major challenges to this is understanding how other molecules, that is, other than those important for making RNA, might affect this process.

The authors think this could be pretty "messy" chemistry in the sense that a lot of other molecules, which could interfere with this process, would be made at the same time. Whether these other molecules will interfere with RNA synthesis, or even have a beneficial effect, is the future focus of these scholars' research. Understanding very complex mixtures of chemicals is not only a challenge in origins of life research, but a major challenge for organic chemistry in general.

The findings are published in Chemistry Select.

Source: Tokyo Institute of Technology [November 29, 2018]

New research reveals the extinction of plant or animal species from extreme environmental change increases the risk of an 'extinction domino effect' that could annihilate all life on Earth.

Virtual earths modelling shows an 'extinction domino effect' risk ten times higher than forecast, indicating rising global temperatures due to climate change could wipeout entire species [Credit: Flinders University]

This would be the worst-case scenario of what scientists call 'co-extinctions', where an organism dies out because it depends on another doomed species, with the findings published in the journal Scientific Reports.

Think of a plant's flower pollinated by only one species of bee -- if the bee becomes extinct, so too will the plant eventually.

"Even the most resilient species will inevitably fall victim to the synergies among extinction drivers as extreme stresses drive ecosystems to collapse." says lead author Dr Giovanni Strona of the European Commission's Joint Research Centre based in Ispra in northern Italy.

Researchers from Italy and Australia simulated 2,000 'virtual earths' linking animal and plant species. Using sophisticated modelling, they subjected the virtual earths to catastrophic environmental changes that ultimately annihilated all life.

Examples of the kinds of catastrophes they simulated included runaway global warming, scenarios of 'nuclear winter' following the detonation of multiple atomic bombs, and a large asteroid impact.

"What we were trying to test is whether the variable tolerances to extreme global heating or cooling by different species are enough to explain overall extinction rates,"


"But because all species are connected in the web of life, our paper demonstrates that even the most tolerant species ultimately succumb to extinction when the less-tolerant species on which they depend disappear."

"Failing to take into account these co-extinctions therefore underestimates the rate and magnitude of the loss of entire species from events like climate change by up to 10 times," says co-author Professor Bradshaw of Flinders University in South Australia

Professor Bradshaw and Dr Strona say that their virtual scenarios warn humanity not to underestimate the impact of co-extinctions.

"Not taking into account this domino effect gives an unrealistic and exceedingly optimistic perspective about the impact of future climate change", warns Professor Bradshaw.

It can be hard to imagine how the demise of a small animal or plant matters so much, but the authors argue that tracking species up to total annihilation demonstrates how the loss of one can amplify the effects of environmental change on the remainder.

"Another really important discovery was that in the case of global warming in particular, the combination of intolerance to heat combined with co-extinctions mean that 5-6 degrees of average warming globally is enough to wipe out most life on the planet", says Dr Strona.

Professor Bradshaw further warns that their work shows how climate warming creates extinction cascades in the worst possible way, when compared to random extinctions or even from the stresses arising from nuclear winter.

Source: Flinders University [November 29, 2018]

Ancient wildfires played a crucial role in the formation and spread of grasslands like those that now cover large parts of the Earth, according to scientists at Penn State and the Smithsonian National Museum of Natural History.

Outcrops in Pakistan provided paleosol, or fossil soil samples, used to test the role of fire in the spread of grasslands nearly 10 million years ago [Credit: Anna K. Behrensmeyer]

A new study links a large rise in wildfires nearly 10 million years ago, in the late Miocene, with a major shift in vegetation on land, as indicated by carbon isotopes of plant biomarkers found in the fossil record. Frequent, seasonal fires helped turn forested areas into open landscapes, and drove the expansion of grasslands, the researchers said.

The team developed an innovative approach to test the role of fire in the rise of early grasslands. They analyzed tracers of ancient leaves and of burned organic matter left behind in paleosols, or fossil soils, in northern Pakistan.

"The tools we use are molecules and biomarkers produced by organisms in Earth history and preserved in rocks," said Allison Karp, a graduate student in geosciences at Penn State and lead author on the paper. "We can use these as clues to figure out what was happening with climate and ecology in the past."

The new technique has broad implications as a tool for scientists seeking to answer questions about past vegetation and climate change, the researcher said.

This shows that the tool can pinpoint the location of a fire where it occurred, according to Karp. "In a paleosol record you are really capturing an integrated picture of what was happening when the soil was forming," she said.

The researchers recently reported their findings in the Proceedings of the National Academy of Sciences. Katherine Freeman, Evan Pugh University Professor of Geosciences at Penn State and Karp's adviser, is a co-author on the paper.

"This is one of the biggest ecological changes in the last 66 million years," said Karp. "None of the open grassland systems we have today existed before this transition. It was a very different looking world, especially in sub-tropical places like Pakistan."

Scientists have long studied the rise of C4 grasslands, named after plants that evolved a new way to handle photosynthesis that allows them to thrive in dry, tropical conditions and with lower amounts of carbon dioxide. These plants include modern crops like corn and sugarcane.

A drop in global carbon dioxide levels was once believed to be behind the rise of C4 grasslands. More recent research has shown that the grasses spread at different rates on different continents, indicating that regional factors, like rain patterns -- and potentially fire -- played important roles. But there had been little direct evidence that linked a rise in wildfires to this transition.

"We were interested in reconstructing fire and the expansion of grasslands in the same geologic record to see if we could find proxy evidence of the role fire played," Karp said. "We now have a nice line of observational evidence to compare to what the models have said."

Karp and her collaborators used polycyclic aromatic hydrocarbons (PAHs), found in paleosols, as fire proxies. PAHs are chemicals that are created by the burning of organic matter like wood and plants. They also are naturally found in coal and crude oil.

PAHs increased five-fold across the study area while evidence of conifer trees declined and ultimately disappeared. The heavily forested landscape opened up in two stages. Around 10 million years ago, forests were replaced by more fire-prone, open woodlands or grasslands, and between six and eight million years ago, C4 grasslands became dominant just as the quantity of fire signatures sharply increased.

Modern fire ecology can explain the process. Grasses grow faster than trees after a fire and they also help create conditions ripe for subsequent fires, promoting open landscapes. In the late Miocene, wet seasons brought on by monsoon conditions encouraged plant growth, which in turn created more fuel for fires during hot, dry seasons in Pakistan.

"The role fire played in the expansion and evolution of grassland systems in deep time is important because understanding how fire has maintained systems in the past can help us predict what may happen to these important systems in the future as climate continues to change," Karp said.

The new fire marker approach could be used to examine landscape-scale interactions between fire and vegetation for other geographic regions and climactic transitions, like glacial-interglacial transitions or catastrophic climate-change events, researchers said.

Author: Matthew James Carroll | Source: Pennsylvania State University [November 28, 2018]