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Tuesday, June 27, 2017

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President Wallace D. Loh Statement on Fliers

March 14, 2017

The white nationalist posters found on college campuses, including our own, contain detestable language that is an affront to who we are, and what we stand for, as the State's flagship university. As a community, we stand for excellence, diversity, and inclusion. We stand against all forms of ignorance and hate. UMPD is investigating this matter as a hate bias.

The University of Maryland, College Park will close tonight, March 13, 2017 at 9 p.m. and will remain closed Tuesday, March 14, 2017 due to expected inclement weather.

March 13, 2017

The University of Maryland, College Park will close tonight, March 13, 2017 at 9 p.m. and will remain closed Tuesday, March 14, 2017 due to expected inclement weather.

Methane-filled Atmosphere of Early Earth Helped ‘Clear the Air’ for Oxygen

March 13, 2017
Contacts: 

Matthew Wright, 301-405-9267

COLLEGE PARK, Md. -- More than 2.4 billion years ago, Earth’s atmosphere was inhospitable, filled with toxic gases that drove wildly fluctuating surface temperatures. New research from the University of Maryland, the University of St. Andrews, NASA’s Jet Propulsion Laboratory, the University of Leeds and the Blue Marble Space Institute of Science suggests that a million-year-long methane haze helped clear the way for today’s world of mild climates and breathable air.

Photo of Earth’s atmosphere filled with a thick, methane-rich haze The team’s new research indicates that this methane-rich haze drove a large amount of hydrogen out of the atmosphere, making room for massive amounts of oxygen.  Their work, published March 13, 2017 in the early online edition of the Proceedings of the National Academy of Sciences, thus proposes a new contributing cause for the “Great Oxidation Event,” which occurred 2.4 billion years ago. During this event, oxygen concentrations in Earth’s atmosphere increased more than 10,000 times, resulting in an atmosphere much like the one that sustains life on Earth today. 

“The transformation of Earth’s air from a toxic mix to a more welcoming, oxygen-rich atmosphere happened in a geological instant,” said James Farquhar, a professor of geology at UMD and a co-author of the study. Farquhar also has an appointment at UMD’s Earth System Science Interdisciplinary Center. “With this study, we finally have the first complete picture of how methane haze made this happen.”

The researchers used detailed chemical records and sophisticated atmospheric models to reconstruct atmospheric chemistry during the time period immediately before the Great Oxidation Event. Their results suggest that ancient bacteria—the only life on Earth at the time—produced massive amounts of methane that reacted to fill the air with a thick haze, resembling the modern-day atmosphere of Saturn’s moon Titan.  

Previous studies by many of the same researchers had identified several such haze events early in Earth’s history. But the current study is the first to show how rapidly these events began and how long they lasted.

“High methane levels meant that more hydrogen, the main gas preventing the build up of oxygen, could escape into outer space, paving the way for global oxygenation,” said Aubrey Zerkle, a biogeochemist at the University of St. Andrews and a co-author of the study. “Our new dataset constitutes the highest resolution record of Archean atmospheric chemistry ever produced, and paints a dramatic picture of Earth surface conditions before the oxygenation of our planet.”

The methane haze persisted for about a million years. After enough hydrogen left the atmosphere, the right chemical conditions took over and the oxygen boom got underway, enabling the evolution of all multicellular life. 

The key to the researchers’ analysis was the discovery of anomalous patterns of sulfur isotopes in the geochemical records from this time. Sulfur isotopes are often used as a proxy to reconstruct ancient atmospheric conditions, but previous investigations into the time period in question had not revealed anything too unusual.

“Reconstructing the evolution of atmospheric chemistry has long been the focus of geochemical research,” said Gareth Izon, lead author of the study, who contributed to the research while a postdoctoral researcher at St. Andrews and is now a postdoctoral researcher at the Massachusetts Institute of Technology. “Our new data show that the chemical composition of the atmosphere was dynamic and, at least in the prelude to the Great Oxidation Event, hypersensitive to biological regulation.” 

This release is based on text provided by the University of St. Andrews.

The research paper, “Biological regulation of atmospheric chemistry en route to planetary oxygenation,” Gareth Izon, Aubrey Zerkle, Kenneth Williford, James Farquar, Simon Poulton, and Mark Claire, was published March 13, 2017 in the Proceedings of the National Academy of Sciences.

This work was supported by the Natural Environment Research Council (Award Nos. NE/H016805 and NE/J023485), the Scottish Alliance for Geoscience, Environment and Society, The Geological Society of London’s Alan and Charlotte Welch Fund, NASA (Award No. NNX12AD91G), The Royal Society, and the European Research Council (Award No. 678812). The content of this article does not necessarily reflect the views of these organizations.


Photo caption:  A period more than 2.4 billion years ago, when Earth’s atmosphere was filled with a thick, methane-rich haze much like Saturn’s moon Titan, seen in an image taken by NASA’s Cassini spacecraft in 2013. Photo credit: NASA/JPL-Caltech/Space Science Institute

 

University of Maryland’s Annual Giving Day Raises Over $2 Million

March 9, 2017
Contacts: 

Katie Lawson, 301-405-4622

COLLEGE PARK, Md. –  The University of Maryland held its fourth annual day of giving on March 8, raising $2,226,934, with 6,355 total gifts from students and parents, faculty and staff, campus organizations, and alumni. Giving Day, a 24-hour giving challenge, supports student scholarships, academic programs, and campus initiatives. 

"Giving Day included contributions from every college and school, dozens of student groups and other units – a true team effort," said University of Maryland President Wallace D. Loh. "With great successes like this, our University’s tremendous momentum continues to build."

Donors were asked to give a minimum gift of $10 to one of the many giving options available-- schools and colleges, athletics, libraries, performing arts, as well as Greek and student organizations-- or to support a specific department or program within a school and college of their choice if it was not listed. Gifts were also donated to several University funds, including the President’s Fearless Fund, which supports the university’s Do Good Institute, and Keep Me Maryland Fund, which provides fast, emergency aid to students at risk of withdrawing from Maryland.

Athletics led the donations with $312,046, followed by the College of Behavioral and Social Sciences and the Robert H. Smith School of Business, who raised $83,602 and $61,296 respectively. The College of Behavioral and Social Sciences saw the highest number of gifts with 611, followed by the A. James Clark School of Engineering, with 491, and the College of Arts and Humanities with 298.

“This year’s Giving Day was a ground-breaking success for the University of Maryland,” said Brian Logue, Senior Director of Annual Giving at UMD. “Through the collaborative efforts of the entire campus, we were able to bring together the university community, locally and beyond, to create excitement around supporting our institution.”

To engage the University of Maryland community in giving, the offices of Annual Giving and University Marketing created hourly challenges and several opportunities for units to receive matching funds, which were donated by Michael and Debbie Schwab and family, the Clarvit family, the College of Education’s Board of Visitors, Robert Satterfield ‘95, Dr. Allen Schick, the School of Public Health, the College of Computer, Mathematical, and Natural Sciences, and Robert Infantino and Doris Campos-Infantino. As donors made gifts, the results were displayed in real time on a leadership board on the website givingday.umd.edu

Leading up to Giving Day, the university generated buzz around the fundraising event with its What’s in the Box?  tease on social media. Giant gift boxes were placed across campus. The contents of the box were revealed on March 8 on the Giving Day website, where visitors were encouraged to provide a gift to the university to help bring Fearless Ideas to life. 

Since its launch in 2013, UMD’s day of giving has raised more than $3,172,774,receiving 12,384 giftsfrom students, alumni, parents, faculty, staff, and friends of the University. 

Scientists Create World’s First Time Crystals

March 8, 2017
Contacts: 

Chris Cesare JQI, 301-405-0824

COLLEGE PARK, Md. -- A team of researchers led by physicists at the University of Maryland-based Joint Quantum Institute (JQI) have created the world’s first time crystal using a chain of atomic ions. 

Photo of Time CrystalsCrystals such as ice or diamond are made of atoms arranged in a repeating pattern in space. These new time crystals have atoms follow a repeating pattern, but in time rather than space. The UMD-led team’s creation brings to life the exotic idea that it might be possible to create such time crystals that was proposed in 2012 by Nobel-prize winning MIT physicist Frank Wilczek.

Much like freezing destroys the symmetry of liquid water, a time crystal disturbs a regularity in time. This is somewhat surprising, says lead author and JQI/ UMD postdoctoral researcher Jiehang Zhang, since nature usually responds in sync to things that change in time. “The earth rotates around the sun once a year, and the seasons have the same period,” Zhang says. “That’s what you would naturally expect.”

A time crystal doesn’t follow this expectation, instead responding with a slower frequency—like a bell struck once a second that rings every other second. The atomic ions in the Maryland experiment, which researchers manipulated using laser pulses, responded exactly half as fast as the sequence of pulses that drove them. Their results are  reported in the March 9 issue of the journal Nature.

Zhang, Christopher Monroe, a UMD Distinguished University Professor of Physics and a JQI Fellow, and a group of experimentalists at UMD teamed up with a theory group at the University of California, Berkeley to create their time crystal. The Berkeley group, led by physicist Norman Yao, had previously proposed a way to create time crystals in the lab. For a chain of atomic ions, the challenge came down to finding the right sequence of laser pulses, along with assembling the sea of mirrors and lenses that ensured the lasers impinged on the ions in the right way.

To create their time crystal, researchers activated three types of laser-driven behavior in a chain of ten ytterbium ions. First, each ion was bombarded with its own individual laser beam, flipping an internal quantum property called spin by roughly 180 degrees with each pulse. Second, the ions were induced to interact with each other, coupling their internal spins together like two neighboring magnets. Finally, random disorder—essentially noise—was sprinkled onto each ion, a feature known from previous experiments to prevent the spins from jostling and heating up the chain. 

Altogether, this sequence twisted around the ions’ spins, and researchers kept track of the orientation of each spin after many repetitions of the sequence. When all three laser-driven behaviors were turned on, the spins of each ion synced up, and they would rhythmically return to their original direction at half the speed of the laser sequence.

But a time crystal is more than mere repetition, and this alone would not be enough to claim the creation of a time crystal, Zhang says. A crystal also needs to be rigid. “If you put a bunch of billiard balls on a pool table separated by exactly 10 centimeters, is that a crystal?” Zhang says.  “Not really, because if you shake the table a little bit it will fall apart.”

Zhang and his colleagues demonstrated that their ions had this rigidity by attempting to artificially “melt” the time crystal. By modifying one of the laser pulses—essentially shaking the table—they observed that the rhythm remained stable, up to a point. Past a certain amount of heating, the time crystal dissolved away, just as an ice cube can melt back into a small puddle of water. But with weak shaking, it remained stable, a fact that provided the key evidence that they had created a time crystal.

This rigidity makes time crystals a potential ingredient for clocking complex quantum systems that have inherent defects and are hard to control. They could have applications to future quantum computers, which will also need to be robust. But such applications are still a long way off, especially since the time crystal that Zhang and collaborators produced lasted less than a millisecond.

“This bizarre state of matter results from a complex interplay between many quantum controls at the individual atomic level,” says UMD’s Monroe. “But time crystals can also emerge in certain solid-state devices, so a general understanding of this phenomenon could help bring such systems into future quantum devices.”

It was with a solid-state device approach that a group of researchers from Harvard University, also working with Berkeley’s Yao, reported the creation of a time crystal. Instead of ions, they used natural defects found in diamond to set up their crystal. The Harvard team’s results also are published in the March 9 issue of Nature.

 

Rapid Changes Point to Origin of Ultra-fast Black Hole “Burps”

March 8, 2017
Contacts: 

 Irene Ying, 301-405-5204

 

COLLEGE PARK, Md. – Gas outflows are common features of active supermassive black holes that reside in the center of large galaxies. Millions to billions of times the mass of the Sun, these black holes feed on the large disks of gas that swirl around them. Occasionally, the black holes eat too much and burp out an ultra-fast wind, or outflow. These winds may have a strong influence on regulating the growth of the host galaxy by clearing the surrounding gas away and suppressing star formation.

Photo of a supermassive black hole Scientists have now made the most detailed observation yet of such an outflow, coming from an active galaxy named IRAS 13224–3809. The outflow’s temperature changed on time scales of less than an hour, which is hundreds of times faster than ever seen before. The rapid fluctuations in the outflow’s temperature indicated that the outflow was responding to X-ray emissions from the accretion disk, a dense zone of gas and other materials that surrounds the black hole. 

The new observations are published in the March 2 issue of the journal Nature.

“Although we have seen these outflows before, this observation was the first time we were able to see the launching of the gases being connected with changes in the luminosity of black holes,” said Erin Kara, a postdoctoral researcher in astronomy at the University of Maryland and a co-author of the study.

Scientists made these measurements using two space telescopes, NASA’s NuSTAR (Nuclear Spectroscopic Telescope Array) telescope and the European Space Agency’s (ESA) XMM-Newton. To capture the variability of these signals, scientists focused the XMM-Newton on the black hole for 17 days in a row, and observed the black hole with NuSTAR for six days.

To measure the temperatures of these winds, scientists studied X-rays coming from the edge of the black hole. As they travel towards Earth, these X-rays pass through the outflows. Elements such as iron or magnesium present in the outflows can absorb specific parts of the X-ray spectrum, creating signature “dips” in the X-ray signal. By observing these dips, called absorption features, astronomers can learn what elements exist in the wind.

The team noticed that the absorption features disappeared and reappeared in the span of a few hours. The researchers concluded that the X-rays were heating up the winds to millions of degrees Celsius, at which point the winds became incapable of absorbing any more X-rays.

The observations that the outflows appear to be linked with X-rays, and that both are so highly variable, provide possible clues for locating where exactly the X-rays and outflows originate.

“The radiating gas flows into black holes are most variable at their centers,” Kara said. “Because we saw such rapid variability in the winds, we know that the emission is coming from very close to the black hole itself, and because we observed that the wind was also changing on rapid time scales, it must also be coming from very close to the black hole.”

To further study galaxy formation and black holes, Chris Reynolds, a professor of astronomy at UMD and a co-PI on the project, noted the need for more detailed data and observations.

“We need to observe this black hole with better and more spectrometers, so we can get more details about these outflows,” Reynolds said. “For instance, we don’t know whether the outflow is composed of one or multiple sheets of gas. And we need to observe on multiple bands in addition to X-rays—that would allow us to detect molecular gases, and colder gases, that can be driven by these high-energy outflows. All that information will be crucial to understanding how these outflows are connected to galaxy formation.” 

The research paper, “Relativistically outflowing gas responds to the inner accretion disk of a black hole," Michael Parker, Ciro Pinto, Andrew Fabian, Anne Lohfink, Douglas Buisson, William Alston, Erin Kara, Edward Cackett, Chia-Ying Chiang, Thomas Dauser, Barbara De Marco, Luigi Gallo, Javier Garcia, Fiona Harrison, Ashley King, Matthew Middleton, Jon Miller, Giovanni Miniutti, Christopher Reynolds, Phil Uttley, Ranjan Vasudevan, Dominic Walton, Daniel Wilkins and Abderahmen Zoghbi, was published in the journal Nature on March 2, 2017.

This research was supported by NASA, the European Space Agency, the European Research Council (Award No. 340492), the European Union Seventh Framework Programme (Award No. n.312789, StrongGravity), and the United Kingdom Science and Technology Facilities Council. The content of this article does not necessarily reflect the views of these organizations.


Photo: Supermassive black hole with X-ray emission emanating from its inner region (pink) and ultra-fast winds streaming from the surrounding disk (purple). Photo credit: European Space Agency

 

University of Maryland Develops New CRISPR-Cpf1 Gene Editing System for Plants

March 3, 2017
Contacts: 

Graham Binder 301-405-9235 

College Park, MD -- Yiping Qi, an assistant professor from the University of Maryland’s College of Agriculture and Natural Resources, and an international research team have developed an upgrade to gene editing technology in plants. This new model is based on the CRISPR-Cpf1, a newer addition to the CRISPR system, which was named as “Breakthrough of the Year” by Science in 2015. Qi’s technology has the potential to establish highly efficient editing systems in crop plants, which will help to ensure the security of our global food system and feed a rapidly growing world population.

While prior groups have utilized CRISPR-Cpf1 on plants, gene editing frequencies have generally been below 50%. Qi’s research utilizes self-cleaving ribozymes - a ribonucleic (RNA) molecule capable of acting as an enzyme - to facilitate precise processing of CRISPR RNA, the key RNA component that mediates DNA targeting. These results established a new system that delivered 100% mutations of target genes in rice crop. This represents a new and cost-effective breeding tool that will help generate elite plant varieties in agriculture within a few generations.  In the same study, the CRISPR-Cpf1 system was also successfully repurposed as a strong gene silencing tool as demonstrated in the plant Arabidopsis, a model organism for studying plant biology.

“This is a very exciting time in CRISPR research, and I’m pleased to unveil this new development in gene editing technology for plants. As scientists and as representatives of our state’s land-grant, we are committed to improving the lives and livelihoods of our residents, and this offers a new approach to growing resilient crops,” said Dr. Qi. “The College of Agriculture is very focused on protecting our nation’s agriculture enterprise and ensuring a sufficient global food supply and I’m excited to help contribute to this important mission throughout advancement in technology.”

In collaboration with researchers from East Carolina University, University of Minnesota and two other Universities in China, Qi and his team recently produced a paper titled “A CRISPR-Cpf1 system for efficient genome editing and transcriptional repression in plants,” which was recently published (link is external) in the research journal Nature Plants. Qi is interested in applying this CRISPR-Cpf1 system in other plant species, including major crops such as maize and wheat. He’s also hoping to encourage other researchers to test his strategy in different organisms for potential improvement of editing efficiency with Cpf1.

UMD Research Finds Young Latino Boys Tend to Have Stable Family Lives, Yet Lag on Academics

March 2, 2017
Contacts: 

Audrey Hill 301-405-3468

COLLEGE PARK, Md. – Researchers led by University of Maryland College of Education Professor Natasha Cabrera have found that Latino boys at nine months of age have similar cognitive and social-emotional skills as their peers and live in stable home environments. Yet by preschool, they lag behind their peers on many academic measures that are used as indicators of future success in school and in the workforce. 

Their recent study examined the development and early home experiences of young Latino boys compared to white boys and Latina girls and the peer-reviewed findings were just published in a research brief that is part of the initiative My Brother's Keeper, which was launched by the Obama administration and is focused on improving the ability of boys of color to achieve success and reach their full potential. The findings of Cabrera and her colleagues provide insight into the development and early home environment of Latino boys and builds a case for early interventions that prepare Latino boys to thrive from the beginning of their academic careers. 

“Our research focused on the early childhood experiences of Latino boys because that is such a crucial time for the development of skills needed for school and life success,” Dr. Cabrera said. “A better understanding of the strengths as well as the difficulties of the home environment and development could help in crafting interventions that improve academic performance for Latino boys.” 

The brief was published by the National Research Center on Hispanic Children and Families as part of its series on Latino families, La Familia: Latino Families Strong and Stable, Despite Limited Resources. The brief was based on a peer-reviewed journal article published in Infant Mental Health Journal in December 2016.  

Cabrera and her research team found that similar to their white peers, Latino boys tend to grow up in homes with high levels of family functioning, which is defined by measures such as parenting stress and couple happiness. The home environments of Latino boys generally function well, despite significantly fewer available parental resources—education and income—and investments relative to white families, as reflected in higher levels of household poverty in Latino homes. 

However, there were differences in the cognitive developmental outcomes and the home experiences of Latino boys, as compared to their white male and Latina female peers:

  • At preschool age, Latino boys lag behind white boys on all academic measures—math (e.g., recognizing numbers, shapes), early reading (e.g., letter identification, conventions of print), and language skills—but not on social skills. In general, these patterns continue to be present at the start of kindergarten.
  • From toddlerhood through kindergarten entry, the differences between Latino boys and Latina girls are fewer, not as persistent, and smaller in magnitude than the differences between Latino boys and white boys.

The research team used data that spanned from birth to entry into kindergarten from the national, large-scale Early Childhood Longitudinal Study.

“Based on the significant difference in academic skills between Latino boys and white boys, which are found by 24 months of age and persist into kindergarten, we recommend that policies and programs that address this achievement gap among Latinos be put into place as early as nine months of age and build on the strengths of these families,” said Dr. Cabrera.

She also recommended programs for Latino parents that encourage them to interact with their young children in ways that support early learning. 

Vigilante Coffee Company Welcomed as Latest Greater College Park Addition

March 2, 2017
Contacts: 

Katie Lawson 301-405-4622

COLLEGE PARK, Md. – Vigilante Coffee Company, LLC—pioneers of specialty coffee in the Washington, D.C. area, specializing in award-winning single origin coffee and coffee education—will open its second café later this year in College Park. Vigilante Coffee Company's expanded presence in the area is another step forward in the University of Maryland’s Greater College Park initiative, a $2 billion public-private investment to rapidly revitalize the Baltimore Avenue corridor and academic campus.

Photo of Viligante Coffee

“The Baltimore Avenue corridor, from the beltway down to Hyattsville, is becoming more vibrant thanks to University leadership, community collaboration and committed business owners like Chris Vigilante," said Ken Ulman, the university's chief strategist for economic development. “This local company embodies the entrepreneurial spirit we work to instill in our students and will be a welcome addition to the many new amenities available to our innovation ecosystem."

Vigilante Coffee Company also plans to help curate and excel student start-ups, while sourcing products from the University. They will lease from the University a now-vacant space located at 8200 Baltimore Avenue, adjacent to campus and the University View and The Varsity apartments. 

 “We are thrilled to become a part of the University of Maryland community, engage in campus life and create a space where people come together,” said Chris Vigilante, Founder, Vigilante Coffee Company. “By working directly with students and faculty we will be creating opportunities to learn about specialty coffee and the business of specialty coffee, as well as sustainability and direct trade within the industry.”  

Vigilante began his career in the coffee industry in the Hawaiian Islands in 2008 where he learned about specialty coffee from farm to cup. Starting in 2012—when Vigilante returned to D.C.—he began roasting coffee to sell at pop-up coffee shops at farmers markets all over D.C., Maryland and Virginia as the Vigilante Coffee Company. That same year, Vigilante Coffee Company made the decision to source their coffees directly and traveled to Colombia.  Today, they travel the world purchasing their coffees directly from small farms. 

Local leaders see Vigilante Coffee Company as a natural fit for the community as Baltimore Avenue continues to evolve and attract new businesses. 

“The City of College Park is thrilled to welcome another local, innovative company to our community, and we are proud of the continued investment by the University and its partners in making College Park a top college town,” said College Park Mayor Patrick L. Wojahn.

“Having a strong City-University partnership is key in helping us attract top amenities to College Park,” said Eric Olson, Executive Director, College Park City-University Partnership. “The collaboration between the City of College Park and the University of Maryland—and investments being made by both—means bringing incredible businesses like Vigilante Coffee Company to the area is just the beginning.” 

The company is adamant about an ethical and sustainable approach in specialty coffee and seek to bridge the gap between their customers and producers. Education is the nucleus of their business—an area where they plan to continue to grow. They believe in giving back to the communities they are a part of and supporting the farming communities that make their coffees possible.  

Earth Likely Began with a Solid Shell

March 1, 2017
Contacts: 

Matthew Wright 301-405-9267

 

COLLEGE PARK, Md.-- Today’s Earth is a dynamic planet with an outer layer composed of giant plates that grind together, sliding past or dipping beneath one another, giving rise to earthquakes and volcanoes. Others separate at undersea mountain ridges, where molten rock spreads out from the centers of major ocean basins. But new research suggests that this was not always the case. Instead, shortly after Earth formed and began to cool, the planet’s first outer layer was a single, solid but deformable shell. Later, this shell began to fold and crack more widely, giving rise to modern plate tectonics.

The research, described in a paper published February 27, 2017 in the journal Nature, is the latest salvo in a long-standing debate in the geological research community-- did plate tectonics start right away—a theory known as uniformitarianism—or did Earth first go through a long phase with a solid shell covering the entire planet? The new results suggest the solid shell model is closest to what really happened.

“Models for how the first continental crust formed generally fall into two groups: those that invoke modern-style plate tectonics and those that do not,” said Michael Brown, a professor of geology at the University of Maryland and a co-author of the study. “Our research supports the latter—a ‘stagnant lid’ forming the planet’s outer shell early in Earth’s history.”

To reach these conclusions, Brown and his colleagues from Curtin University and the Geological Survey of Western Australia studied rocks collected from the East Pilbara Terrane, a large area of ancient granitic crust located in the state of Western Australia. Rocks here are among the oldest known, ranging from 3.5 to about 2.5 billion years of age. (Earth is roughly 4.5 billion years old.) The researchers specifically selected granites with a chemical composition usually associated with volcanic arcs—a telltale sign of plate tectonic activity.

Brown and his colleagues also looked at basalt rocks from the associated Coucal formation. Basalt is the rock produced when volcanoes erupt, but it also forms the ocean floor, as molten basalt erupts at spreading ridges in the center of ocean basins. In modern-day plate tectonics, when ocean floor basalt reaches the continents, it dips—or subducts—beneath the Earth’s surface, where it generates fluids that allow the overlying mantle to melt and eventually create large masses of granite beneath the surface.

Previous research suggested that the Coucal basalts could be the source rocks for the granites in the Pilbara Terrane, because of the similarities in their chemical composition. Brown and his collaborators set out to verify this, but also to test another long-held assumption-- could the Coucal basalts have melted to form granite in some way other than subduction of the basalt beneath Earth’s surface? If so, perhaps plate tectonics was not yet happening when the Pilbara granites formed.

To address this question, the researchers performed thermodynamic calculations to determine the phase equilibria of average Coucal basalt. Phase equilibria are precise descriptions of how a substance behaves under various temperature and pressure conditions, including the temperature at which melting begins, the amount of melt produced and its chemical composition.

For example, one of the simplest phase equilibria diagrams describes the behavior of water--at low temperatures and/or high pressures, water forms solid ice, while at high temperatures and/or low pressures, water forms gaseous steam. Phase equilibria gets a bit more involved with rocks, which have complex chemical compositions that can take on very different mineral combinations and physical characteristics based on temperature and pressure.

“If you take a rock off the shelf and melt it, you can get a phase diagram. But you’re stuck with a fixed chemical composition,” Brown said. “With thermodynamic modeling, you can change the composition, pressure and temperature independently. It’s much more flexible and helps us to answer some questions we can’t address with experiments on rocks.”

Using the Coucal basalts and Pilbara granites as a starting point, Brown and his colleagues constructed a series of modeling experiments to reflect what might have transpired in an ancient Earth without plate tectonics. Their results suggest that, indeed, the Pilbara granites could have formed from the Coucal basalts.

More to the point, this transformation could have occurred in a pressure and temperature scenario consistent with a “stagnant lid,” or a single shell covering the entire planet.

Plate tectonics substantially affects the temperature and pressure of rocks within Earth’s interior. When a slab of rock subducts under the Earth’s surface, the rock starts off relatively cool and takes time to gain heat. By the time it reaches a higher temperature, the rock has also reached a significant depth, which corresponds to high pressure—in the same way a diver experiences higher pressure at greater water depth.

In contrast, a “stagnant lid” regime would be very hot at relatively shallow depths and low pressures. Geologists refer to this as a “high thermal gradient.”

“Our results suggest the Pilbara granites were produced by melting of the Coucal basalts or similar materials in a high thermal gradient environment,” Brown said. “Additionally, the composition of the Coucal basalts indicates that they, too, came from an earlier generation of source rocks. We conclude that a multi-stage process produced Earth’s first continents in a ‘stagnant lid’ scenario before plate tectonics began.”

This work was supported by The Institute of Geoscience Research at Curtin University, Perth, Australia. The content of this article does not necessarily reflect the views of this organization.


Photo caption: The outer layer of modern Earth is a collection of interlocking rigid plates. Credit: USGS

 

 

 

 

 

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