Hot spot at Hawaii? Not so fast

– AUGUST 18, 2017

Hot spot at Hawaii? Not so fast

Rice University scientists’ model shows global mantle plumes don’t move as quickly as thought

HOUSTON – (Aug. 18, 2017) – Through analysis of volcanic tracks, Rice University geophysicists have concluded that hot spots like those that formed the Hawaiian Islands aren’t moving as fast as recently thought.

Hot spots are areas where magma pushes up from deep Earth to form volcanoes. New results from geophysicist Richard Gordon and his team confirm that groups of hot spots around the globe can be used to determine how fast tectonic plates move.

Rice University geophysicists have developed a method that uses the average motion of hot-spot groups by plate to determine that the spots aren't moving as fast as geologists thought. For example, the Juan Fernandez Chain (outlined by the white rectangle) on the Nazca Plate west of Chile was formed by a hot spot now at the western end of the chain as the Nazca moved east-northeast relative to the hotspot forming the chain that includes Alejandro Selkirk and Robinson Crusoe islands. The white arrow shows the direction of motion of the Nazca Plate relative to the hot spot, and it is nearly indistinguishable from the direction predicted from global plate motions relative to all the hot spots on the planet (green arrow). The similarity in direction indicates that very little motion of the Juan Fernandez hot spot relative to other hot spots is needed to explain its trend. Illustration by Chengzu Wang

Gordon, lead author Chengzu Wang and co-author Tuo Zhang developed a method to analyze the relative motion of 56 hot spots grouped by tectonic plates. They concluded that the hot-spot groups move slowly enough to be used as a global reference frame for how plates move relative to the deep mantle. This confirmed the method is useful for viewing not only current plate motion but also plate motion in the geologic past.

The study appears in Geophysical Research Letters.

Hot spots offer a window into the depths of Earth, as they mark the tops of mantle plumes that carry hot, buoyant rock from deep Earth to near the surface and produce volcanoes. These mantle plumes were once thought to be straight and stationary, but recent results suggested they can also shift laterally in the convective mantle over geological time.

The primary evidence of plate movement relative to the deep mantle comes from volcanic activity that forms mountains on land, islands in the ocean or seamounts, mountain-like features on the ocean floor. A volcano forms on a tectonic plate above a mantle plume. As the plate moves, the plume gives birth to a series of volcanoes. One such series is the Hawaiian Islands and the Emperor Seamount Chain; the youngest volcanoes become islands while the older ones submerge. The series stretches for thousands of miles and was formed as the Pacific Plate moved over a mantle plume for 80 million years.

Rice University geophysicists have developed a method that uses the average motion of hot-spot groups by plate to determine that the spots aren’t moving as fast as geologists thought. From left, Chengzu Wang, Richard Gordon and Tuo Zhang. Photo by Jeff Fitlow

The Rice researchers compared the observed hot-spot tracks with their calculated global hot-spot trends and determined the motions of hot spots that would account for the differences they saw. Their method demonstrated that most hot-spot groups appear to be fixed and the remainder appear to move slower than expected.

“Averaging the motions of hot-spot groups for individual plates avoids misfits in data due to noise,” Gordon said. “The results allowed us to say that these hot-spot groups, relative to other hot-spot groups, are moving at about 4 millimeters or less a year.

“We used a method of analysis that’s new for hot-spot tracks,” he said. “Fortunately, we now have a data set of hot-spot tracks that is large enough for us to apply it.”

For seven of the 10 plates they analyzed with the new method, average hot-spot motion measured was essentially zero, which countered findings from other studies that spots move as much as 33 millimeters a year. Top speed for the remaining hot-spot groups — those beneath the Eurasia, Nubia and North America plates — was between 4 and 6 millimeters a year but could be as small as 1 millimeter per year. That’s much slower than most plates move relative to the hot spots. For example, the Pacific Plate moves relative to the hot spots at about 100 millimeters per year.

Gordon said those interested in paleogeography should be able to make use of the model. “If hot spots don’t move much, they can use them to study prehistorical geography. People who are interested in circum-Pacific tectonics, like how western North America was assembled, need to know that history of plate motion.

“Others who will be interested are geodynamicists,” he said. “The motions of hot spots reflect the behavior of mantle. If the hot spots move slowly, it may indicate that the viscosity of mantle is higher than models that predict fast movement.”

“Modelers, especially those who study mantle convection, need to have something on the surface of Earth to constrain their models, or to check if their models are correct,” Wang said. “Then they can use their models to predict something. Hot-spot motion is one of the things that can be used to test their models.”

Gordon is the W.M. Keck Professor of Earth Science. Wang and Zhang are Rice graduate students. The National Science Foundation supported the research.

 

Read the paper at http://onlinelibrary.wiley.com/doi/10.1002/2017GL073430/full

Data mining finds more than expected beneath Andean Plateau

Seismic data suggests means of producing massive volumes of continental crust

Seismologists investigating how Earth forms new continental crust have compiled more than 20 years of seismic data from a wide swath of South America’s Andean Plateau and determined that processes there have produced far more continental rock than previously believed.

“When crust from an oceanic tectonic plate plunges beneath a continental tectonic plate, as it does beneath the Andean Plateau, it brings water with it and partially melts the mantle, the layer below Earth’s crust,” said Rice University’s Jonathan Delph, co-author of the new study published online this week in Scientific Reports. “The less dense melt rises, and one of two things happens: It either stalls in the crust to crystallize in formations called plutons or reaches the surface through volcanic eruptions.”

Jonathan Delph

Delph, a Wiess Postdoctoral Research Associate in Rice’s Department of Earth, Environmental and Planetary Science, said the findings suggest that mountain-forming regions like the Andean Plateau, which geologists refer to as “orogenic plateaus,” could produce much larger volumes of continental rock in less time than previously believed.

Study lead author Kevin Ward, a postdoctoral researcher at the University of Utah, said, “When we compared the amount of trapped plutonic rock beneath the plateau with the amount of erupted volcanic rock at the surface, we found the ratio was almost 30:1. That means 30 times more melt gets stuck in the crust than is erupted, which is about six times higher than what’s generally believed to be the average. That’s a tremendous amount of new material that has been added to the crust over a relatively short time period.”

A true-color image of the Central Andes and surrounding landscape acquired by the Moderate-resolution Imaging Spectroradiometer (MODIS), flying aboard NASA’s Terra spacecraft. (Image courtesy of NASA)

The Andean Plateau covers much of Bolivia and parts of Peru, Chile and Argentina. Its average height is more than 12,000 feet, and though it is smaller than Asia’s Tibetan Plateau, different geologic processes created the Andean Plateau. The mountain-building forces at work in the Andean plateau are believed to be similar to those that worked along the western coast of the U.S. some 50 million years ago, and Delph said it’s possible that similar forces were at work along the coastlines of continents throughout Earth’s history.

Most of the rocks that form Earth’s crust initially came from partial melts of the mantle. If the melt erupts quickly, it forms basalt, which makes up the crust beneath the oceans on Earth; but there are still questions about how continental crust, which is more buoyant than oceanic crust, is formed. Delph said he and Ward began their research in 2016 as they were completing their Ph.D.s at the University of Arizona. The pair spent several months combining public datasets from seismic experiments by several U.S. and German institutions. Seismic energy travels through different types of rock at different speeds, and by combining datasets that covered a 500-mile-wide swath of the Andean Plateau, Ward and Delph were able to resolve large plutonic volumes that had previously been seen only in pieces.

West-east cross sections from north (top) to south (bottom) of a 500-mile-wide portion of the Andean Plateau show subsurface features to a depth of 80 kilometers. Colors represent the speed at which seismic waves pass through the Earth; arrows point to plutonic regions of continent-building material in each section. (Image courtesy of J. Delph/Rice University)

Over the past 11 million years, volcanoes have erupted thousands of cubic miles’ worth of material over much of the Andean Plateau. Ward and Delph calculated their plutonic-to-volcanic ratio by comparing the volume of regions where seismic waves travel extremely slowly beneath volcanically active regions, indicating some melt is present, with the volume of rock deposited on the surface by volcanoes.

“Orogenic oceanic-continental subduction zones have been common as long as modern plate tectonics have been active,” Delph said. “Our findings suggest that processes similar to those we observe in the Andes, along with the formation of supercontinents, could have been a significant contributor to the episodic formation of buoyant continental crust.”

Additional co-authors include George Zandt and Susan Beck of the University of Arizona and Mihai Ducea of the University of Arizona and University of Bucharest.

The research was supported by the National Science Foundation and Rice University, and data was obtained by request from the Incorporated Research Institutions for Seismology and the German Research Centre for Geosciences, Potsdam.

 

Hidden river once flowed beneath Antarctic ice

Antarctic researchers from Rice University have discovered one of nature’s supreme ironies: On Earth’s driest, coldest continent, where surface water rarely exists, flowing liquid water below the ice appears to play a pivotal role in determining the fate of Antarctic ice streams.

Rice University researchers (from left) Lindsay Prothro, Lauren Simkins and John Anderson and colleagues discovered a long-dead river system that once flowed beneath Antarctica’s ice. (Photo by Jeff Fitlow/Rice University)

The finding, which appears online this week in Nature Geoscience, follows a two-year analysis of sediment cores and precise seafloor maps covering 2,700 square miles of the western Ross Sea. As recently as 15,000 years ago, the area was covered by thick ice that later retreated hundreds of miles inland to its current location. The maps, which were created from state-of-the-art sonar data collected by the National Science Foundation research vessel Nathaniel B. Palmer, revealed how the ice retreated during a period of global warming after Earth’s last ice age. In several places, the maps show ancient water courses — not just a river system, but also the subglacial lakes that fed it.

Today, Antarctica is covered by ice that is in some places more than 2 miles thick. Though deep, the ice is not static. Gravity compresses the ice, and it moves under its own weight, creating rivers of ice that flow to the sea. Even with the best modern instruments, the undersides of these massive ice streams are rarely accessible to direct observation.

This schematic depicts a subglacial Antarctic river and overlying ice sheet. Black lines t1, t2 and t3 show where the ice sheet was grounded to the seafloor during pauses in ice retreat. Rice University researchers used such lines from precise maps of the Ross Sea floor to study how liquid water influenced the ice sheet during a period of its retreat starting about 15,000 years ago. (Image courtesy of L. Prothro/Rice University)

“One thing we know from surface observations is that some of these ice streams move at velocities of hundreds of meters per year,” said Rice postdoctoral researcher Lauren Simkins, lead author of the new study. “We also know that ice, by itself, is only capable of flowing at velocities of no more than tens of meters per year. That means the ice is being helped along. It’s sliding on water or mud or both.”

Because of the paucity of information about how water presently flows beneath Antarctic ice, Simkins said the fossilized river system offers a unique picture of how Antarctic water drains from subglacial lakes via rivers to the point where ice meets sea.

“The contemporary observations we have of Antarctic hydrology are recent, spanning maybe a couple decades at best,” Simkins said. “This is the first observation of an extensive, uncovered, water-carved channel that is connected to both subglacial lakes on the upstream end and the ice margin on the downstream end. This gives a novel perspective on channelized drainage beneath Antarctic ice. We can track the drainage system all the way back to its source, these subglacial lakes, and then to its ultimate fate at the grounding line, where freshwater mixed with ocean water.”

An example of seafloor bathymetry data that Rice University oceanographers used to identify a paleo-subglacial channel, grounding line landforms, volcanic seamounts and other features used in their study. (Image courtesy of L. Simkins/Rice University)

Simkins said meltwater builds up in subglacial lakes. First, intense pressures from the weight of ice causes some melting. In addition, Antarctica is home to dozens of volcanoes, which can heat ice from below. Simkins found at least 20 lakes in the fossil river system, along with evidence that water built up and drained from the lakes in episodic bursts rather than a steady stream. She worked with Rice co-author and volcanologist Helge Gonnermann to confirm that nearby volcanoes could have provided the necessary heat to feed the lakes.

Study co-author John Anderson, a Rice oceanographer and veteran of nearly 30 Antarctic research expeditions, said the size and scope of the fossilized river system could be an eye-opener for ice-sheet modelers who seek to simulate Antarctic water flow. For example, the maps show exactly how ice retreated across the channel-lake system. The retreating ice stream in the western Ross Sea made a U-turn to follow the course of an under-ice river. Simkins said that’s notable because “it’s the only documented example on the Antarctic seafloor where a single ice stream completely reversed retreat direction, in this case to the south and then to the west and finally to the north, to follow a subglacial hydrological system.”

Location of study area in the western Ross Sea. (Image courtesy of L. Simkins/Rice University)

Simkins and Anderson said the study may ultimately help hydrologists and modelers better predict how today’s ice streams will behave and how much they’ll contribute to rising sea levels.

“It’s clear from the fossil record that these drainage systems can be large and long-lived,” Anderson said. “They play a very important role in the behavior of the ice sheet, and most numerical models today are not at a state where they can deal with that kind of complexity.”

He said another key finding is that drainage through the river system took place on a time scale measured in tens to several hundreds of years.

“We’re kind of in this complacent mode of thinking right now,” Anderson said. “Some people say, ‘Well, the ice margin seems to be stable.’ Some people may take comfort in that, but I don’t because what this new research is telling us is that there are processes that operate on decadal time scales that influence ice behavior. The probability of us having observed a truly stable condition in the contemporary system, given our limited observation time, is pretty low.”

Additional co-authors are Lindsay Prothro of Rice, Sarah Greenwood of Stockholm University, Anna Ruth Halberstadt and Robert DeConto of the University of Massachusetts-Amherst, Leigh Stearns of the University of Kansas and David Pollard of Pennsylvania State University.

The research was supported by the National Science Foundation and the Swedish Research Council.

New plate adds plot twist to ancient tectonic tale

Rice University scientists say Malpelo microplate helps resolve geological misfit under Pacific Ocean

By Mike Williams
713-348-6728
mikewilliams@rice.edu

HOUSTON – (Aug. 14, 2017) – A microplate discovered off the west coast of Ecuador adds another piece to Earth’s tectonic puzzle, according to Rice University scientists.

Researchers led by Rice geophysicist Richard Gordon discovered the microplate, which they have named “Malpelo,” while analyzing the junction of three other plates in the eastern Pacific Ocean. 

The Malpelo Plate, named for an island and an underwater ridge it contains, is the 57th plate to be discovered and the first in nearly a decade, they said. They are sure there are more to be found.

Misfit plates in the Pacific led Rice University scientists to the discovery of the Malpelo Plate between the Galapagos Islands and the South American coast. Click on the image for a larger version. Illustration by Tuo Zhang

The research by Gordon, lead author Tuo Zhang and co-authors Jay Mishra and Chengzu Wang, all of Rice, appears in Geophysical Research Letters.

How do geologists discover a plate? In this case, they carefully studied the movements of other plates and their evolving relationships to one another as the plates move at a rate of millimeters to centimeters per year. 

The Pacific lithospheric plate that roughly defines the volcanic Ring of Fire is one of about 10 major rigid tectonic plates that float and move atop Earth’s mantle, which behaves like a fluid over geologic time. Interactions at the edges of the moving plates account for most earthquakes experienced on the planet. There are many small plates that fill the gaps between the big ones, and the Pacific Plate meets two of those smaller plates, the Cocos and Nazcawest of the Galapagos Islands. 

One way to judge how plates move is to study plate-motion circuits, which quantify how the rotation speed of each object in a group (its angular velocity) affects all the others. Rates of seafloor spreading determined from marine magnetic anomalies combined with the angles at which the plates slide by each other over time tells scientists how fast the plates are turning.

“When you add up the angular velocities of these three plates, they ought to sum to zero,” Gordon said. “In this case, the velocity doesn’t sum to zero at all. It sums to 15 millimeters a year, which is huge.”

Rice University researchers have discovered a microplate off the coast of South America. From left, Tuo Zhang, Richard Gordon and Chengzu Wang. Photo by Jeff Fitlow

That made the Pacific-Cocos-Nazca circuit a misfit, which meant at least one other plate in the vicinity had to make up the difference. Misfits are a cause for concern – and a clue.

Knowing the numbers were amiss, the researchers drew upon a Columbia University database of extensive multibeam sonar soundings west of Ecuador and Colombia to identify a previously unknown plate boundary between the Galapagos Islands and the coast.  

Previous researchers had assumed most of the region east of the known Panama transform fault was part of the Nazca plate, but the Rice researchers determined it moves independently. “If this is moving in a different direction, then this is not the Nazca plate,” Gordon said. “We realized this is a different plate and it’s moving relative to the Nazca.”

Evidence for the Malpelo plate came with the researchers’ identification of a diffuse plate boundary that runs from the Panama Transform Fault eastward to where the diffuse plate boundary intersects a deep oceanic trench just offshore of Ecuador and Colombia. 

“A diffuse boundary is best described as a series of many small, hard-to-spot faults rather than a ridge or transform fault that sharply defines the boundary of two plates,” Gordon said. “Because earthquakes along diffuse boundaries tend to be small and less frequent than along transform faults, there was little information in the seismic record to indicate this one’s presence.” 

“With the Malpelo accounted for, the new circuit still doesn’t close to zero and the shrinking Pacific Plate isn’t enough to account for the difference either,” Zhang said. “The nonclosure around this triple junction goes down — not to zero, but only to 10 or 11 millimeters a year. 

“Since we’re trying to understand global deformation, we need to understand where the rest of that velocity is going,” he said. “So we think there’s another plate we’re missing.” 

Plate 58, where are you?

Gordon is the W.M. Keck Professor of Geophysics. Zhang and Wang are Rice graduate students and Mishra is a Rice alumnus. 

The National Science Foundation supported the research.

Read the abstract at http://onlinelibrary.wiley.com/doi/10.1002/2017GL073704/full

This news release can be found online at http://news.rice.edu/2017/08/13/new-plate-adds-plot-twist-to-ancient-tectonic-tale/

 

Glaciers may have helped warm Earth

Glaciers may have helped warm Earth

Rice professor’s study details effect of glacial versus nonglacial weathering on carbon cycle

It seems counterintuitive, but over the eons, glaciers may have made Earth warmer, according to a Rice University professor.

Weathering of Earth by glaciers may have warmed Earth over eons by aiding the release of carbon dioxide into the atmosphere.
A new study shows the cumulative effect may have created negative feedback that prevented runaway glaciation.
Photo by Paul Quackenbush

Mark Torres, an assistant professor of Earth, environmental and planetary sciences, took a data-driven dive into the mechanics of weathering by glaciation over millions of years to see how glacial cycles affected the oceans and atmosphere and continue to do so.


Mark Torres

Torres, who joined the Rice faculty in July, is lead author of a paper in the Proceedings of the National Academy of Sciences. He wanted to know how and when chemicals released by weathering of the land reached the atmosphere and ocean, and what effect they have had.

The study shows that glaciation, through enhanced erosion, probably increased the rate of carbon dioxide released to the environment. The researchers determined enhanced oxidation of pyrite, an iron sulfide also known as fool’s gold, most likely generated acidity that fed carbon dioxide into the oceans and altered the carbon cycle. The oscillation of glaciers over 10,000 years could have changed atmospheric carbon dioxide by 25 parts per million or more. While this is a significant percentage of the 400 parts per million measured in recent months, present anthropogenic carbon dioxide release is occurring at a much faster rate than it is naturally released by glaciation.

Over long timescales, they found, glaciers’ contribution to the release of carbon dioxide could have acted as a negative feedback loop that may have inhibited runaway glaciation.“The ocean stores a lot of carbon,” Torres said. “If you change the chemistry of the ocean, you can release some of that stored carbon into the atmosphere as carbon dioxide. This release of carbon dioxide affects Earth’s climate, due to the greenhouse effect.”

Glacial runoff appeared to have an outsize effect on carbon dioxide levels compared with that of rivers in warmer climes. Torres, until recently a postdoctoral researcher at the California Institute of Technology, studied glacier-fed rivers and used existing databases to compare their chemical contents with that of thousands of rivers around the world.

The goal was to evaluate the dominant chemical reactions associated with glacial weathering and explore the long-term implications. “Mainly, we’re thinking about the effect of glaciers and glaciation on the way our planet works,” he said. “In particular, we’re looking at rivers that drain areas of land surface that are covered by glaciers, and whether or not there are any differences in the chemical composition of those rivers.”

Mark Torres, an assistant professor of Earth, environmental and planetary sciences,
looked into the mechanics of weathering by glaciation over millions of years to see
how glacial cycles affected the oceans and atmosphere.

The researchers acknowledged that glaciers are equal-opportunity weathering agents, as they also break down silicates in rocks. Silicates release alkalinity that removes carbon from the atmosphere. Still, they believe the net effect of glaciation could be to supply carbon dioxide to the atmosphere rather than to remove it.

The results support a couple of interesting additional theories. One is that billions of years ago in the Archeaneon and Paleoproterozoic era, when the atmosphere contained little oxygen, Earth may indeed have been a “snowball” as oxidative weathering in glaciated regions and the subsequent release of carbon would have been less active. Another is that the growth of a sulfide reservoir in Earth’s crust over time may have helped to stabilize the climate, which is important for maintaining Earth’s habitability over geologic timescales.

The paper’s authors include Nils Moosdorf of the Center for Tropical Marine Ecology in Bremen, Germany, Jens Hartmann of the University of Hamburg, Jess Adkins of the California Institute of Technology and A. Joshua West of the University of Southern California.

Glacial weathering, sulfide oxidation, and global carbon cycle feedbacks PNAS 2017 published ahead of print July 31, 2017doi:10.1073/pnas.1702953114

 

Biochar could clear the air in more ways than one

New research by Professor Carrie Masiello’s Post-Doctoral Fellow Ghasideh Pourhashem is highlighted.  

“I really like her team’s work because it models a couple of important parts of environmental science – the fundamental team nature of problem-solving (her team’s work required integrating soil science, air quality, and health economics), and then also the idea that addressing environmental problems does not mean just pointing out that something doesn’t work, or even taking the next step of identifying a solution.  We also have to keep going and look at the economics of the solution, the potential unintended consequences, and the social implications of solutions.  In this case they identified a positive unintended consequence, and Ghasideh’s team was able to show the extra financial benefits from the process.  I hope that her team created a little more of a financial incentive for this particular technology!” —Dr. Carrie Masiello

Rice University study suggests health, economic benefits of capturing agricultural nitric oxide

 

MIKE WILLIAMS – JULY 26, 2017

HOUSTON – (July 26, 2017) – Biochar from recycled waste may both enhance crop growth and save health costs by helping clear the air of pollutants, according to Rice University researchers.

Rice researchers in Earth science, economics and environmental engineering have determined that widespread use of biochar in agriculture could reduce health care costs, especially for those who live in urban areas close to farmland.

Biochar is ground charcoal produced from waste wood, manure or leaves. Added to soil, the porous carbon has been shown to boost crop yields, lessen the need for fertilizer and reduce pollutants by storing nitrogen that would otherwise be released to the atmosphere.

Using biochar to cut emissions of nitric oxide (NO) and nitrogen dioxide (NO2) would lower ozone and particulate matter levels in urban areas near farmland and save lives and money, according to Rice University researchers. Illustration by Ghasideh Pourhashem

The study led by Ghasideh Pourhashem, a postdoctoral fellow at Rice’s Baker Institute for Public Policy, appears in the American Chemical Society journal Environmental Science and Technology.

Pourhashem worked with environmental engineering graduate student Quazi Rasool and postdoc Rui Zhang, Rice Earth scientist Caroline Masiello, energy economist Ken Medlock and environmental scientist Daniel Cohan to show that urban dwellers in the American Midwest and Southwest would gain the greatest benefits in air quality and health from greater use of biochar.

 

Biochar could reduce local air pollution from agriculture by reducing emissions of nitric oxide from soil, according to Rice University researchers. Courtesy of Ghasideh Pourhashem

They said the U.S. counties that would stand to save the most in health care costs from reduced smog are Will, La Salle and Livingston counties in Illinois; San Joaquin, San Diego, Fresno and Riverside counties in California; Weld County in Colorado; Maricopa County in Arizona; and Fort Bend County in Texas.

“Our model projections show health care cost savings could be on the order of millions of dollars per year for some urban counties next to farmland,” Pourhashem said. “These results are now ready to be tested by measuring changes in air pollutants from specific agricultural regions.”

Pourhashem noted the key measurements needed are the rate of soil emission of nitric oxide (NO), which is a smog precursor, after biochar is applied to fields. Many studies have already shown that biochar reduces the emissions of a related compound, nitrous oxide, but few have measured NO.

“We know that biochar impacts the soil nitrogen cycle, and that’s how it reduces nitrous oxide,” said Masiello, a professor of Earth, environmental and planetary science. “It likely reduces NO in the same way. We think the local impact of biochar-driven NO reductions could be very important.”

Ghasideh Pourhashem

NO contributes to urban smog and acid rain. NO also is produced by cars and power plants, but the Rice study focused on its emission from fertilized soils.

The Rice team used data from three studies of NO emissions from soil in Indonesia and Zambia, Europe and China. The data revealed a wide range of NO emission curtailment — from 0 percent to 67 percent — depending on soil type, meteorological conditions and the chemical properties of biochar used.

Using the higher figure in their calculations, they determined that a 67 percent reduction in NO emissions in the United States could reduce annual health impacts of agricultural air pollution by up to $660 million. Savings through the reduction of airborne particulate matter — to which NO contributes — could be 10 times larger than those from ozone reduction, they wrote.

“Agriculture rarely gets considered for air pollution control strategies,” said Cohan, an associate professor of civil and environmental engineering. “Our work shows that modest changes to farming practices can benefit the air and soil too.”

Medlock is the James A. Baker III and Susan G. Baker Fellow in Energy and Resource Economics and senior director of the Center for Energy Studies at Rice’s Baker Institute for Public Policy and lecturer of economics.

The research was supported by the NASA Air Quality Applied Sciences Team, Rice’s Shell Center for Sustainability and the Baker Institute.

Read the abstract at http://pubs.acs.org/doi/10.1021/acs.est.7b00748

This news release can be found online at news.rice.edu

 

Zealandia should hold answers about tectonics and past climate

Zealandia should hold answers about tectonics, past climate

JADE BOYD – JULY 18, 2017

Scientific expedition will explore Tasman Sea for clues about submerged continent

Thirty scientists will sail from Australia July 27 on a two-month ocean drilling expedition to the submerged continent of Zealandia in search of clues about its history, which relates to key questions about plate tectonic processes and Earth’s past greenhouse climate.

Jerry Dickens standing on a map of Zealandia in Rice’s Keith-Wiess Geological Laboratories (Photo by Jeff Fitlow/Rice University)

“We’re really looking at the best place in the world to understand how plate subduction initiates,” said expedition co-chief scientist Gerald Dickens, professor of Earth, environmental and planetary science at Rice University. “This expedition will answer a lot of lingering questions about Zealandia.”

Expedition 371, a cruise sponsored by the National Science Foundation and its international partners in the International Ocean Discovery Program (IODP), will sail from Townsville, Australia, aboard JOIDES Resolution, one of the world’s most sophisticated scientific drill ships. Expedition scientists will join more than 20 scientific crew members in drilling at six Tasman Sea sites at water depths ranging from 1,000 to 5,000 meters. At each site, the crew will drill from 300 to 800 meters into the seafloor to collect cores — complete samples of sediments deposited over millions of years. The cores hold fossil evidence the scientists can use to assemble a detailed record of Zealandia’s past.

“Some 50 million years ago a massive shift in plate movement happened in the Pacific Ocean,” said Jamie Allan, program director in the National Science Foundation’s Division of Ocean Sciences, which supports IODP. “It resulted in the diving of the Pacific Plate under New Zealand, the uplift of New Zealand above the waterline and the development of a new arc of volcanoes. This IODP expedition will look at the timing and causes of these changes, as well as related changes in ocean circulation patterns and ultimately Earth’s climate.”

IODP Expedition 371 map (Image courtesy IODP)

Zealandia is a mass of continental crust about half the size of Australia that surrounds New Zealand. Increasingly detailed seafloor maps have brought Zealandia into focus in recent decades. Unlike other continents, though, more than 90 percent of Zealandia is submerged.

“If you go way back, about 100 million years ago, Antarctica, Australia and Zealandia were all one continent,” Dickens said. “Around 85 million years ago, Zealandia split off on its own, and for a time, the seafloor between it and Australia was spreading on either side of an ocean ridge that separated the two.”

The relative movements of Zealandia and Australia are due to plate tectonics, the constant movement of interlocking sections of Earth’s surface. There are some 25 tectonic plates that fit like puzzle pieces to form Earth’s crust. Plates are in constant motion. They can crash together to form mountain ranges and slide past one another in earthquake zones. Oceanic plates form on either side of ocean ridges and also can slide beneath lighter, more buoyant continental plates in a process known as subduction.

JOIDES Resolution (Photo courtesy IODP)

Expedition 371 will examine a shift that occurred about 50 million years ago in the direction of movement of the enormous Pacific Plate northeast of Zealandia. In its scientific prospectus, the expedition refers to this shift as “the most profound subduction initiation event and global plate-motion change” in the past 80 million years. Prior to the shift, Australia and New Zealand were spreading apart, and after the shift, the area that separated them was under compression for millions of years. Then, in the final stage of the tectonic shift, the Pacific Plate dove beneath Zealandia, forming a new subduction zone. This relieved the compressive forces across the region.

“What we want to understand is why and when the various stages from extension to relaxation occurred,” Dickens said. “The cores will help tell us that. They’ll be analyzed for sediment composition, microfossil components, mineral and water chemistry and physical properties.”

He said the research also could answer many questions about the way Earth’s climate has evolved in the last 60 million years. For example, Zealandia is left out of many climate models, and Dickens said this could be one reason that this region has been among the most difficult parts of Earth to accurately model in greenhouse climates around 50 million years ago.

“When the community does climate modeling for the Eocene (Epoch), this is the area that causes consternation, and we’re not sure why,” he said. “It may be because we had continents that were much shallower than we had thought. Or we could have the continents right but at the wrong latitude. Either way, the cores will help us figure that out.”

IODP is an international research collaboration that coordinates seagoing expeditions to study the history of Earth recorded in sediments and rocks beneath the ocean floor. Scientists apply to participate in IODP expeditions, and participation is open to all scientists from IODP’s member countries. Opportunities exist for researchers, including graduate students, in all shipboard specialties, which include but are not limited to sedimentology, micropaleontology, paleomagnetism, inorganic/organic geochemistry, petrology, petrophysics, microbiology and borehole geophysics. For more information, visit http://iodp.tamu.edu/index.html.

JR in a Minute the Whole Ship!

 

Seismic CT scan points to rapid uplift of Southern Tibet

 

JUNE 7, 2017

By Jade Boyd

Tomographic model indicates Southern Tibet formed within 10 million years  

HOUSTON — (June 7, 2017) — Using seismic data and supercomputers, Rice University geophysicists have conducted a massive seismic CT scan of the upper mantle beneath the Tibetan Plateau and concluded that the southern half of the “Roof of the World” formed in less than one-quarter of the time since the beginning of India-Eurasia continental collision.

Rice University geophysicists conducted a seismic CT scan of the upper mantle (figure above) beneath the Tibetan Plateau and concluded that that most of the uplift across Southern Tibet occurred within 10 million years due to the breakaway of a thickened segment of lithosphere that today extends at least 660 kilometers below the plateau. (Image courtesy of M. Chen/Rice University)

 

The research, which appears online this week in the journal Nature Communications, finds that the high-elevation of Southern Tibet was largely achieved within 10 million years. Continental India’s tectonic collision with Asia began about 45 million years ago.

“The features that we see in our tomographic image are very different from what has been seen before using traditional seismic inversion techniques,” said Min Chen, the Rice research scientist who headed the project. “Because we used full waveform inversion to assimilate a large seismic data set, we were able to see more clearly how the upper-mantle lithosphere beneath Southern Tibet differs from that of the surrounding region. Our seismic image suggests that the Tibetan lithosphere thickened and formed a denser root that broke away and sank deeper into the mantle. We conclude that most of the uplift across Southern Tibet likely occurred when this lithospheric root broke away.”

 

 

The research could help answer longstanding questions about Tibet’s formation. Known as the “Roof of the World,” the Tibetan Plateau stands more than three miles above sea level. The basic story behind its creation — the tectonic collision between the Indian and Eurasian continents — is well-known to schoolchildren the world over, but the specific details have remained elusive. For example, what causes the plateau to rise and how does its high elevation impact Earth’s climate?

“The leading theory holds that the plateau rose continuously once the India-Eurasia continental collision began, and that the plateau is maintained by the northward motion of the Indian plate, which forces the plateau to shorten horizontally and move upward simultaneously,” said study co-author Fenglin Niu, a professor of Earth science at Rice. “Our findings support a different scenario, a more rapid and pulsed uplift of Southern Tibet.”

Min Chen (Photo by Jeff Fitlow/Rice University)

 

 

It took three years for Chen and colleagues to complete their tomographic model of the crust and upper-mantle structure beneath Tibet. The model is based on readings from thousands of seismic stations in China, Japan and other countries in East Asia. Seismometers record the arrival time and amplitude of seismic waves, pulses of energy that are released by earthquakes and that travel through Earth. The arrival time of a seismic wave at a particular seismometer depends upon what type of rock it has passed through. Working backward from instrument readings to calculate the factors that produced them is something scientists refer to as an inverse problem, and seismological inverse problems with full waveforms incorporating all kinds of usable seismic waves are some of the most complex inverse problems to solve.

 

(Figure at right ) The collision of the Indian and Eurasian continental plates began about 45 million years ago and caused lithospheric thickening that led to (a) uplift of the Tibetan Plateau due to convective removal of a thickened segment of lithosphere 30 million to 25 million years ago, (b) magmatism in Southern Tibet 25 million to 15 million years ago, (c) decrease of magmatism in Southern Tibet due to northward underthrusting of the Indian plate’s lithosphere 15 million to 10 million years ago and (d) ongoing magmatism today in Northern Tibet. (Image courtesy of M. Chen/Rice University)

Chen and colleagues used a technique called full waveform inversion, “an iterative full waveform-matching technique that uses a complicated numerical code that requires parallel computing on supercomputers,” she said.

“The technique really allows us to use all the wiggles on a large number of seismographs to build up a more realistic 3-D model of Earth’s interior, in much the same way that whales or bats use echo-location,” she said. “The seismic stations are like the ears of the animal, but the echo that they are hearing is a seismic wave that has either been transmitted through or bounced off of subsurface features inside Earth.”

The tomographic model includes features to a depth of about 500 miles below Tibet and the Himalaya Mountains. The model was computed on Rice’s DAVinCI computing cluster and on supercomputers at the University of Texas that are part of the National Science Foundation’s Extreme Science and Engineering Discovery Environment (XSEDE).

“The mechanism that led to the rise of Southern Tibet is called lithospheric thickening and foundering,” Chen said. “This happened because of convergence of two continental plates, which are each buoyant and not easy to subduct underneath the other plate. One of the plates, in this case on the Tibetan side, was more deformable than the other, and it began to deform around 45 million years ago when the collision began. The crust and the rigid lid of upper mantle — the lithosphere — deformed and thickened, and the denser lower part of this thickened lithosphere eventually foundered, or broke off from the rest of the lithosphere. Today, in our model, we can see a T-shaped section of this foundered lithosphere that extends from a depth of about 250 kilometers to at least 660 kilometers.”

Chen said that after the denser lithospheric root broke away, the remaining lithosphere under Southern Tibet experienced rapid uplift in response.

“The T-shaped piece of foundered lithosphere sank deeper into the mantle and also induced hot upwelling of the asthenosphere, which leads to surface magmatism in Southern Tibet,” she said.

Such magmatism is documented in the rock record of the region, beginning around 30 million years ago in an epoch known as the Oligocene.

“The spatial correlation between our tomographic model and Oligocene magmatism suggests that the Southern Tibetan uplift happened in a relatively short geological span that could have been as short as 5 million years,” Chen said.

Additional co-authors include Adrian Lenardic, Cin-Ty Lee, Wenrong Cao and Julia Ribeiro, all of Rice, and Jeroen Tromp of Princeton University.

The research was supported by a grant from the National Science Foundation (NSF), by the NSF’s Extreme Science and Engineering Discovery Environment (XSEDE) program, and by the China Earthquake Administration’s China Seismic Array Data Management Center. Rice’s DAVinCI supercomputer is administered by Rice’s Center for Research Computing and procured in partnership with the Ken Kennedy Institute for Information Technology.

 

High-resolution IMAGES are available for download at:

http://news.rice.edu/files/2017/06/0607_TIBET-fitlow14-lg-1vrjuae.jpg
CAPTION: Min Chen (Photo by Jeff Fitlow/Rice University)

http://news.rice.edu/files/2017/06/0607_TIBET-3Dfront-lg-1yvcz73.jpg
CAPTION: Rice University geophysicists conducted a seismic CT scan of the upper mantle beneath the Tibetan Plateau and concluded that that most of the uplift across Southern Tibet occurred within 10 million years due to the breakaway of a thickened segment of lithosphere that today extends at least 660 kilometers below the plateau. (Image courtesy of M. Chen/Rice University)

http://news.rice.edu/files/2017/06/0607_TIBET-figure-lg-1svqq6l.jpg
CAPTION: The collision of the Indian and Eurasian continental plates began about 45 million years ago and caused lithospheric thickening that led to (a) uplift of the Tibetan Plateau due to convective removal of a thickened segment of lithosphere 30 million to 25 million years ago, (b) magmatism in Southern Tibet 25 million to 15 million years ago, (c) decrease of magmatism in Southern Tibet due to northward underthrusting of the Indian plate’s lithosphere 15 million to 10 million years ago and (d) ongoing magmatism today in Northern Tibet. (Image courtesy of M. Chen/Rice University)

https://eol.jsc.nasa.gov/searchphotos/photo.pl?mission=STS41G&roll=120&frame=22
TITLE: STS41G-120-0022
CAPTION: The Tibetan Plateau as seen from Space Shuttle Challenger in October 1984. (Image courtesy of NASA)

The DOI of the Nature Communications paper is: 10.1038/NCOMMS15659

A copy of the paper, “Lithospheric Foundering and Underthrusting Imaged Beneath Tibet,” is available at: https://www.nature.com/articles/ncomms15659

More information is available at:

Rice Earth Science: https://earthscience.rice.edu/

Rice Research Computing: https://oit.rice.edu/research-computing

Min Chen home page: https://sites.google.com/site/minchenresearch/

XSEDE: https://www.xsede.org/

TACC: https://www.tacc.utexas.edu/

This release can be found online at news.rice.edu.

– See more at: http://news.rice.edu/2017/06/07/seismic-ct-scan-points-to-rapid-uplift-of-southern-tibet/#sthash.UJGcQGuI.dpuf

 

Nittrouer and Ma featured in New York Times Science News

From June 6-Dateline Rice:

A new formula to help tame China’s Yellow River

 Jeffrey Nittrouer, assistant professor of Earth science, and postdoctoral research associate Hongbo Ma are highlighted in the New York Times, Science news.

U.S. and Chinese geologists studying China’s Yellow River have created a new tool that could help Chinese officials better predict and prevent the river’s all-too-frequent floods, which threaten as many as 80 million people. The new tool, a physics-based formulation to calculate sediment transport, can also be applied to study the sustainability of eroding coastlines worldwide.

New York Times 

June 2, 2017

http://nyti.ms/2s9IJdW

Carrie Masiello- 2017 Geological Society of America Fellow

Society Fellowship is an honor bestowed on the best of our profession by election at the spring GSA Council meeting. GSA members are nominated by existing GSA Fellows in recognition of their distinguished contributions to the geosciences through such avenues as publications, applied research, teaching, administration of geological programs, contributing to the public awareness of geology, leadership of professional organizations, and taking on editorial, bibliographic, and library responsibilities.

Dr. Carrie Masiello has been a professor of Earth, Environmental, and Planetary Sciences at Rice University since 2004, and is jointly appointed in the departments of Chemistry and Biosciences.  Her research bridges organic geochemistry, soil science and geology.

Masiello’s research focuses on the development and application of tools to understand the cycling and fate of carbon in the Earth system.  Much of her work has involved the use of radiocarbon, nuclear magnetic resonance, and various other forms of spectroscopy and microscopy to understand the cycling and fate of charcoal in the Earth system.  The behavior of charcoal in the environment is relevant both in theoretical and applied contexts: charcoal’s environmental recalcitrance leads to an important role in the long-term storage of carbon in the Earth system, and in addition, it is being intentionally added to soils to store carbon and improve crop performance.  Masiello’s work has contributed to both our theoretical understanding of the mechanisms controlling charcoal’s environmental recalcitrance and to our understanding of the mechanisms driving its ability to alter agronomic processes.

Most recently her work has expanded to include the application of new synthetic biology tools to understanding microbial processes driving carbon, nitrogen, and water fluxes in the Earth system. Masiello was one of the first Earth scientists to recognize that the new capabilities of synthetic biology could be used in the construction of laboratory tools to address hard theoretical problems in carbon and nitrogen cycling. She leads a Rice team that was recently awarded 1 million dollars by the Keck Foundation to  build new microbial biosensors appropriate for soil and marine science applications.  These organisms report in on their environmental experiences (e.g. temperature, moisture, nutrient status) and/or their decision-making (e.g. horizontal gene transfer, greenhouse-gas emissions, pathogenicity) by releasing non-volatile gases.

Lastly, Masiello is deeply committed to creative teaching, science outreach, and advocacy for underrepresented groups in science. She has mentored the research experiences of 27 undergraduates, 14 of whom are underrepresented minorities, and 19 of whom are women.  Her research group regularly hosts public school teachers from local school districts, mentoring them through the development of Earth science curricular materials appropriate for the K-12 community. She also has collaborated with Rice’s Program in Writing and Communication and the Center for Teaching Excellence in expanding students’ skills in writing and public speaking, both within existing classes and through the creating of capstone communication courses.