Former piece of Pacific Ocean floor imaged deep beneath China

JADE BOYD – NOVEMBER 16, 2020

Study offers clues about the fate of tectonic plates that sink deep in Earth’s mantle

In a study that gives new meaning to the term “rock bottom,” seismic researchers have discovered the underside of a rocky slab of Earth’s surface layer, or lithosphere, that has been pulled more than 400 miles beneath northeastern China by the process of tectonic subduction.

A graphic showing the convective heat cycle (red arrows) that drives plate tectonic motion (black arrows) on Earth. Heat flows toward subduction zones through the uppermost mantle layer, the asthenosphere. A computer model from Rice University finds that the asthenosphere can locally drag plates along with it rather than acting exclusively as a brake on plate movements as had been widely believed. (Image courtesy of Surachit/Wikimedia Commons)

The study, published by a team of Chinese and U.S. researchers in Nature Geoscience, offers new evidence about what happens to water-rich oceanic tectonic plates as they are drawn through Earth’s mantle beneath continents.

Rice University seismologist Fenglin Niu, a co-corresponding author, said the study provides the first high-resolution seismic images of the top and bottom boundaries of a rocky, or lithospheric, tectonic plate within a key region known as the mantle transition zone, which starts about 254 miles (410 kilometers) below Earth’s surface and extends to about 410 miles (660 kilometers).

“A lot of studies suggest that the slab actually deforms a lot in the mantle transition zone, that it becomes soft, so it’s easily deformed,” Niu said. How much the slab deforms or retains its shape is important for explaining whether and how it mixes with the mantle and what kind of cooling effect it has.

Earth’s mantle convects like heat in an oven. Heat from Earth’s core rises through the mantle at the center of oceans, where tectonic plates form. From there, heat flows through the mantle, cooling as it moves toward continents, where it drops back toward the core to collect more heat, rise and complete the convective circle.

Fenglin Niu (Photo courtesy of Rice University)

Previous studies have probed the boundaries of subducting slabs in the mantle, but few have looked deeper than 125 miles (200 kilometers) and none with the resolution of the current study, which used more than 67,000 measurements collected from 313 regional seismic stations in northeastern China. That work, which was done in collaboration with the China Earthquake Administration, was led by co-corresponding author Qi-Fu Chen from the Chinese Academy of Sciences.

The research probes fundamental questions about the processes that shaped Earth’s surface over billions of years. Mantle convection drives the movements of Earth’s tectonic plates, rigid interlocked pieces of Earth’s surface that are in constant motion as they float atop the asthenosphere, the topmost mantle layer and the most fluid part of the inner planet.

Where tectonic plates meet, they jostle and grind together, releasing seismic energy. In extreme cases, this can cause destructive earthquakes and tsunamis, but most seismic motion is too faint for humans to feel without instruments. Using seismometers, scientists can measure the magnitude and location of seismic disturbances. And because seismic waves speed up in some kinds of rock and slow in others, scientists can use them to create images of Earth’s interior, in much the same way a doctor might use ultrasound to image what’s inside a patient.

Illustration of the subduction of an oceanic lithospheric plate sliding beneath a continental plate. (Modified from image provided courtesy of Booyabazooka/Wikimedia Commons)

Niu, a professor of Earth, environmental and planetary sciences at Rice, has been at the forefront of seismic imaging for more than two decades. When he did his Ph.D. training in Japan more than 20 years ago, researchers were using dense networks of seismic stations to gather some of the first detailed images of the submerged slab boundaries of the Pacific plate, the same plate that was imaged in study published this week.

“Japan is located about where the Pacific plate reaches around 100-kilometer depths,” Niu said. “There is a lot of water in this slab, and it produces a lot of partial melt. That produces arc volcanoes that helped create Japan. But, we are still debating whether this water is totally released in that depth. There is increasing evidence that a portion of the water stays inside the plate to go much, much deeper.”

Northeastern China offers one of the best vantage points to investigate whether this is true. The region is about 1,000 kilometers from the Japan trench where the Pacific plate begins its plunge back into the planet’s interior. In 2009, with funding from the National Science Foundation and others, Niu and scientists from the University of Texas at Austin, the China Earthquake Administration, the Earthquake Research Institute of Tokyo University and the Research Center for Prediction of Earthquakes and Volcanic Eruptions at Japan’s Tohoku University began installing broadband seismometers in the region.

“We put 140 stations there, and of course the more stations the better for resolution,” Niu said. “The Chinese Academy of Sciences put additional stations so they can get a finer, more detailed image.”

Seismic imaging in northeastern China revealed both the top (X1) and bottom (X2) boundaries of a tectonic plate (blue) that formerly sat at bottom of the Pacific Ocean and is being pulled into Earth’s mantle transition zone, which lies about 254-410 miles (410-660 kilometers) beneath Earth’s surface. (Image courtesy of F. Niu/Rice University)

In the new study, data from the stations revealed both the upper and lower boundaries of the Pacific plate, dipping down at a 25-degree angle within the mantle transition zone. The placement within this zone is important for the study of mantle convection because the transition zone lies below the asthenosphere, at depths where increased pressure causes specific mantle minerals to undergo dramatic phase changes. These phases of the minerals behave very differently in seismic profiles, just as liquid water and solid ice behave very different even though they are made of identical molecules. Because phase changes in the mantle transition zone happen at specific pressures and temperatures, geoscientists can use them like a thermometer to measure the temperature in the mantle.

Niu said the fact that both the top and bottom of the slab are visible is evidence that the slab hasn’t completely mixed with the surrounding mantle. He said heat signatures of partially melted portions of the mantle beneath the slab also provide indirect evidence that the slab transported some of its water into the transition zone.

“The problem is explaining how these hot materials can be dropped into the deeper part of the mantle,” Niu said. “It’s still a question. Because they are hot, they are buoyant.”

Illustration of a process where holes in the subducting Pacific plate would allow heat to escape, driving volcanic activity in the Changbaishan region at the border of China and North Korea, even as the plate continues to sink into the mantle. (Image courtesy of F. Niu/Rice University)

That buoyancy should act like a life preserver, pushing upward on the underside of the sinking slab. Niu said the answer to this question could be that holes have appeared in the deforming slab, allowing the hot melt to rise while the slab sinks.

“If you have a hole, the melt will come out,” he said. “That’s why we think the slab can go deeper.”

Holes could also explain the appearance of volcanos like the Changbaishan on the border between China and North Korea.

“It’s 1,000 kilometers away from the plate boundary,” Niu said. “We don’t really understand the mechanism of this kind of volcano. But melt rising from holes in the slab could be a possible explanation.”

Study co-authors include Xin Wang and Juan Li, both of the Chinese Academy of Sciences, Shengji Wei of Singapore’s Nanyang Technological University, Weijun Wang of the China Earthquake Administration, Johannes Buchen of the California Institute of Technology and Lijun Liu of the University of Illinois at Urbana-Champaign. The research was funded by the Chinese Academy of Sciences and the National Natural Science Foundation of China.

Biochar helps hold water, saves money

– OCTOBER 19, 2020

The abstract benefits of biochar for long-term storage of carbon and nitrogen on American farms are clear, and now new research from Rice University shows a short-term, concrete bonus for farmers as well.

That would be money. To be precise, money not spent on irrigation.

In the best-case scenarios for some regions, extensive use of biochar could save farmers a little more than 50% of the water they now use to grow crops. That represents a significant immediate savings to go with the established environmental benefits of biochar.

Biochar’s benefits for the long-term sequestration of carbon and nitrogen on American farms are clear, but new research from Rice University shows it can help farmers save money on irrigation as well. The study showed that sandy soil, in particular, gains ability to retain more water when amended with biochar. Courtesy of the Masiello Lab

The open-access study appears in the journal GCB-Bioenergy.

Biochar is basically charcoal produced through pyrolysis, the high-temperature decomposition of biomass, including straw, wood, shells, grass and other materials. It has been the subject of extensive study at Rice and elsewhere as the agriculture industry seeks ways to enhance productivity, sequester carbon and preserve soil.

The new model built by Rice researchers explores a different benefit, using less water.

“There’s a lot of biochar research that focuses mostly on its carbon benefits, but there’s fairly little on how it could help stakeholders on a more commercial level,” said lead author and Rice alumna Jennifer Kroeger, now a fellow at the Science and Technology Policy Institute in Washington, D.C. “It’s still an emerging field.”

The study co-led by Rice biogeochemist Caroline Masiello and economist Kenneth Medlock provides formulas to help farmers estimate irrigation cost savings from increased water-holding capacity (WHC) with biochar amendment.

Jennifer Kroeger

Jennifer Kroeger

The researchers used their formulas to reveal that regions of the country with sandy soils would see the most benefit, and thus the most potential irrigation savings, with biochar amendment, areas primarily in the southeast, far north, northeast and western United States.

The study analyzes the relationship between biochar properties, application rates and changes in WHC for various soils detailed in 16 existing studies to judge their ability to curtail irrigation.

The researchers defined WHC as the amount of water that remains after allowing saturated soil to drain for a set period, typically 30 minutes. Clay soils have a higher WHC than sandy soils, but sandy soils combined with biochar open more pore space for water, making them more efficient.

WHC is also determined by pore space in the biochar particles themselves, with the best results from grassy feedstocks, according to their analysis.

In one comprehensively studied plot of sandy soil operated by the University of Nebraska-Lincoln’s Agricultural Water Management Network, Kroeger calculated a specific water savings of 37.9% for soil amended with biochar. Her figures included average rainfall and irrigation levels for the summer of 2019.

The researchers noted that lab experiments typically pack more biochar into a soil sample than would be used in the field, so farmers’ results may vary. But they hope their formula will be a worthy guide to those looking to structure future research or maximize their use of biochar.

More comprehensive data for clay soils, along with better characterization of a range of biochar types, will help the researchers build models for use in other parts of the country, they wrote.

A map shows low, mid-range and high estimates for theoretical water-holding capacity changes in soil with the addition of biochar. A study by Rice University scientists showed how biochar can help curtail excess irrigation in agriculture, depending on the type of soil and biochar characteristics. Courtesy of the Masiello Lab

“This study draws attention to the value of biochar amendment especially in sandy soils, but it’s important to note that the reason we are calling out sandy soils here is because of a lack of data on finer-textured soils,” Masiello said. “It’s possible that there are also significant financial benefits on other soil types as well; the data just weren’t available to constrain our model under those conditions.”

“Nature-based solutions are gaining traction at federal, state and international levels,” Medlock added, noting the recently introduced Growing Climate Solutions Act as one example. “Biochar soil amendment can enhance soil carbon sequestration while providing significant co-benefits, such as nitrogen remediation, improved water retention and higher agricultural productivity. The suite of potential benefits raises the attractiveness for commercial action in the agriculture sector as well as supportive policy frameworks.”

Rice alumna Ghasideh Pourhashem, a nonresident faculty scholar at the Center for Energy Studies (CES) at Rice’s Baker Institute for Public Policy, is co-author of the paper. Masiello is the W. Maurice Ewing Professor, a professor of Earth, environmental and planetary sciences and a faculty scholar at the CES. Medlock is the James A. Baker, III, and Susan G. Baker Fellow in Energy and Resource Economics at the Baker Institute, senior director of the CES and an adjunct assistant professor of economics.

The Rice Department of Earth, Environmental and Planetary Sciences and the Rice Shell Center for Sustainability supported the research.

Study: Darwin’s theory about coral reef atolls is fatally flawed

– OCTOBER 12, 2020

 

Scientists compile new evidence that atolls are formed by cyclic changes in sea level

Marine geologist and oceanographer André Droxler knows Charles Darwin’s theory about atolls is incorrect. But Droxler, who’s studied coral reefs for more than 40 years, understands why Darwin’s model persists in textbooks, university lecture halls, natural science museums and Wikipedia entries.

“It’s so beautiful, so simple and pleasing that everybody still teaches it,” said Droxler, who recently retired from Rice University. “Every introductory book you can find in Earth science and marine science still has Darwin’s model. If they teach one thing about reefs or carbonates in marine science 101, they teach that model.”

André Droxler (Photo by Jeff Fitlow/Rice University)

Droxler, a professor of Earth, environmental and planetary sciences at Rice for 33 years, is hoping to set the record straight with a 37-page, tour de force paper about the origins of atolls. Published this month in the Annual Review of Marine Science, the paper was co-authored by Droxler and longtime collaborator Stéphan Jorry, a marine geologist and oceanographer at the French Research Institute for Exploitation of the Sea (IFREMER).

Darwin’s theory about the formation of atolls was published in 1842, six years after his legendary voyage aboard the British survey ship HMS Beagle. A geologist by training, Darwin was keenly interested in the rocks and landforms he encountered in his five years aboard the Beagle. The ship’s primary mission was surveying coastlines and hazards to navigation, and the ship’s orders included collecting detailed observations of the tides and ocean depths around a coral atoll.

“They spent a lot of time mapping reefs because they were such hazards to shipping,” Droxler said of the Royal Navy. Atolls were particularly interesting and dangerous. Some were topped with low-lying islands but many were jagged rings of coral-topped rock that sat just below the water’s surface, ready to rip the bottom out of unwary passing ships. “They come out of the abyssal plain of the ocean to almost no depth,” Droxler said. “So they needed to know exactly where they were located.”

The Beagle, like every Royal Navy vessel, carried charts with the marked location of every known reef, and Darwin put these to use in his 1842 paper.

“He published a beautiful map that compiled all the known reefs on Earth,” Droxler said. “It’s amazing, when you compare satellite images of reefs today versus his map. It’s almost the same. It’s unbelievably accurate.”

A comparison of contemporary Google Earth satellite images (right) and Charles Darwin’s 1842 maps (left) for: Vanikoro fringing reef, Solomon Islands (top), Chuuck barrier reef, Micronesia (middle); and Peros Banhos Atoll, Chagos Archipelago, Indian Ocean. (bottom). (Images courtesy A. Droxler)

But unlike navy maps that simply marked reefs as hazards to navigation, Darwin systematically classified each into one of three categories. Those attached to land, he called fringing reefs. Those detached from land and separated by a lagoon were barrier reefs. The third category was atolls, ring reefs that enclosed a central lagoon but no land.

At the time, geologists believed continents were steadily rising out of the Earth and oceans were steadily sinking. Darwin noticed that both fringing and barrier reefs tended to surround volcanic islands, and he reasoned reefs initially formed on the fringe of volcanic islands. When the volcano died and slowly sank back into the ocean, the reef remained, first becoming a separated barrier reef and eventually, after the volcano sank entirely, an atoll.

Droxler said he’s awed by Darwin’s ability to synthesize all that was known about reefs in his day and come up with such a simple, comprehensive and compelling theoretical model. But beauty aside, Darwin could not have accurately predicted how atolls form because he lacked the key piece of information, Droxler said.

“Cyclic changes in sea level drive atoll formation,” Droxler said. “Darwin had no concept that sea level could go up and down, because glaciation didn’t become common knowledge until the 1860s.”

Droxler said the simplicity of Darwin’s classification system and theory could play a role in its continued appeal. A more accurate description of atoll formation has been around since the 1930s, but it is considerably more complicated and much of the evidence to support it is more recent, coming in the past 40 years from dozens of scientific and oil industry drilling expeditions as well as from the compiled record of Earth’s climate and sea level history.

Today’s atolls formed in the past 500,000 years, Droxler said, driven by five wild swings in sea level that occurred every 100,000 years. In each cycle, sea level rose and fell by 120 meters or more. But to fully appreciate how changing sea level created atolls, it helps to start much earlier, Droxler said.

“The Earth’s climate has changed quite dramatically in the last 5 million years,” he said. “From about 5 million years ago to 2.5 million years ago, we had a rather warm climate that did not change very much, and sea level remained relatively constant. At that time, the Earth was producing flat-topped banks where today we have atolls.”

Sea level rose steadily but slowly, and the flat-topped banks that would give birth to atolls were created by countless generations of corals and other sea creatures that lived and died, adding their skeletons to the mineralized floor of the shallow, flat-topped marine ecosystem. The flat-top banks grew steadily, keeping pace with sea level until the warm period ended about 2.5 million years ago.

South Keeling Island, one of 27 atolls in the Indian Ocean’s Cocos Islands, as seen from NASA’s Earth Observing-1 satellite on July 31, 2009. The Cocos, about 800 miles southeast of Jakarta, Indonesia, were visited by Charles Darwin in April 1836 during his voyage aboard the HMS Beagle. (Photo by Jesse Allen and Robert Simmon, provided courtesy of NASA’s EO-1)

“The climate began to fluctuate into cycles,” Droxler said. “There were alternate periods of warm and cold, but overall, the trend was that the Earth’s climate got colder and colder and colder, interrupted by short warm swings.”

Throughout this period, ice caps were thickening. As ice accumulated, sea level fell, exposing the tops of the flat carbonate banks, which rose out of the ocean like bleached stone mesas. When rain fell atop the exposed banks, it slowly dissolved the carbonate, and standing water sped up the process. Puddles and ponds gradually carved bowl-like depressions. And over 2 million years, this process turned white mesas into ring-like towers with hollowed-out central depressions.

“Ice volume on Earth reached its initial maximum around 500,000-600,000 years ago, when a mile of ice covered Chicago, and New York was at the southern edge of a massive ice sheet on North America, comparable to modern Antarctica,” Droxler said “There was so much ice in North America, Scotland, Scandinavia and Siberia that sea level was reaching 120 meters to 130 meters below what it is today.”

The five dramatic swings in sea level that occurred in the past half-million years were driven by Earth’s ability to form large northern ice sheets, and by the sensitivity of those ice sheets to slight climatic changes, like fluctuations in the amount of sunlight landing in the far Northern Hemisphere due to slight changes in the planet’s orbit and tilt.

“Because these big ice sheets formed in North America, not on the pole, but centered in relatively low latitude about 65 degrees north, they accumulated huge ice volumes that lowered sea level by more than 120 meters,” he said. “But also, they were able to melt very quickly. And so we observe, now, these cyclic high-amplitude swings of sea level. And the first big swing was about at 450,000 years ago, when it went from minus-135 meters to plus-10 meters of what we have today.”

Stéphan Jorry, a postdoctoral research associate at Rice University from 2005-06, is a marine geologist and oceanographer at the French Research Institute for Exploitation of the Sea (IFREMER). (Photo courtesy of S. Jorry/IFREMER)

During each swing, the hollowed out flat-topped banks were resubmerged during warm periods, when sea level rose near its highest level. During those periods, as today, coral recolonized the highest parts of the eroded banks, in particular along their raised outer rims.

“Now you’re adding carbonate on to their raised rim, and you’re creating the modern atolls,” Droxler said. “But this period of high sea level doesn’t last for more than 10,000-12,000 years, and it goes down again. So now you are adding some reef on the rim, but then dissolving the lagoon again when sea level retreats. So you are enhancing the morphology even more with each cycle now, growing on the margin and dissolving in the middle.”

Droxler’s and Jorry’s in-depth study contains dozens of illustrations, including some comparisons of Darwin’s original drawings with contemporary maps and satellite imagery. And the paper draws on decades of marine geological data compiled from dozens of expeditions, including recent datasets acquired by both co-authors in the Indian Ocean. Droxler said he and Jorry had discussed such a paper for years, but it might not have happened without the 2020 pandemic.

Droxler moved to a remote ranch in Central Texas after retiring, and when the pandemic shut down travel in March, he was faced with the prospect of being there for some time.

“For years, Stéphan had pushed me, saying we should publish this, but you know, you always kind of do something else and something else,” Droxler said. “At the end of March, Stéphan called me and said, ‘I’m stuck in France, at home, and you’re stuck in the middle of the countryside in Mason County. Let’s write this paper.’ And so that’s what we did.”

The research was supported by the National Science Foundation, Royal Dutch Shell, Total, the Environmental Protection Agency of the Maldives, the University of South Florida and the Passive Margins Exploration Laboratories research program of IFREMER, Total, the French National Center for Scientific Research, the University of Rennes, the University of Western Brittany, Pierre and Marie Curie University and the French Institute of Petroleum.

Ocean water could melt precarious Antarctic glacier

– SEPTEMBER 28, 2020

Rice helps study threats to Thwaites, a glacier that could add 25 inches to sea level

Rice University researchers, alumni and staff are part of an international effort that has discovered a pathway for warm ocean water to melt the underside of Thwaites Glacier, a precarious body of west Antarctic ice that could add as much as 25 inches to global sea level if it were to suffer a runaway collapse.

Blocks of dense, blue ice the size of convenience stores can be seen breaking away from Thwaites Glacier in a February 2019 photograph taken from the deck of the research vessel Nathaniel B. Palmer. (Photo by Linda Welzenbach)

In two papers published this month in the journal The Cryosphere, a team of U.S. and British scientists detailed deep seabed channels beneath Thwaites, which covers an area approximately the size of the state of Florida and is particularly susceptible to climate and ocean changes.

Glaciers are moving bodies of ice that flow downhill. Thwaites flows into the Amundsen Sea, and already accounts for 4% of global sea-level rise each year. The amount of ice Thwaites dumps into the ocean each year is five times greater than it was 30 years ago.

Rice Antarctic expert John Anderson, co-author of one of the papers, said the research brings attention to an impact of climate change that has gotten little attention in a year when the global COVID-19 pandemic competed for headlines with “unprecedented drought and wildfires in the west, record temperatures at the poles and what is potentially going to be a record year for severe storms and their impacts.”

“History will record the year 2020 as one filled with eye-opening impacts of climate change,” said Anderson, Rice’s W. Maurice Ewing Professor Emeritus of Oceanography. “One example is global sea-level rise, which is occurring at about five times the rate of a century ago and causing significant impact on coastal areas across the globe.”

John Anderson

It’s well-established that ocean warming and the melting of glaciers and ice sheets are increasing rates of sea level rise. The melting of thick ice sheets atop Greenland and Antarctica have the most potential to increase sea level, but scientists still do not understand all the factors that influence ice sheet stability. Thwaites is especially remote and little studied.

“The Greenland Ice Sheet shows clear signs of accelerated decay, with vast areas experiencing melting and retreat that is clearly observed from space,” Anderson said. “But, melting of the Antarctic Ice Sheet has remained more elusive because the ice sheet is melting from its base and is less obvious to scientists.”

Thwaites is part of the West Antarctic Ice Sheet, which is about two miles thick and sits mostly on land below sea level. Because water extends far beneath Thwaites, it is particularly vulnerable to a runaway collapse, which occurs when a glacier lifts off the continent and slides into the ocean.

Because Thwaites has the potential to increase sea level so much, the United Kingdom and the United States have funded a joint effort, the International Thwaites Glacier Collaboration, to study the glacier in detail. The two papers published this month resulted from the collaboration’s first data-gathering missions in January-March 2019.

More than a mile of the seaward edge of Thwaites Glacier, as seen from the deck of the research vessel Nathaniel B. Palmer in February 2019. The glacier covers an area the size of Florida and sits atop land that lies below sea level. (Photo by Linda Welzenbach)

 

Anderson, a veteran of more than two dozen Antarctic expeditions, is a member of the collaboration’s Thwaites Offshore Research (THOR) project, as are three former members of his research group – Julia Wellner ’01 of the University of Houston, Rebecca Totten Minzoni ’14, of the University of Alabama and Lauren Simkins of the University of Virginia. Rice science writer and photographer Linda Welzenbach, a science communications specialist in the Department of Earth, Environmental and Planetary Sciences, is also a THOR member.

Minzoni and Welzenbach sailed with THOR aboard the National Science Foundation icebreaker Nathanial B. Palmer in 2019 to map the seafloor in front of the glacier. Welzenbach served as the mission’s public outreach coordinator and photographer. THOR’s maps revealed networks of deep-sea channels that allow water from the Amundsen Sea to reach the cold underbellies of both Thwaites and its neighbor, Pine Island Glacier.

“This discovery is an important step in estimating the volumes of water, and therefore heat, that are reaching the ice,” Anderson said. “Scientists need that information to predict future ice loss and associated sea-level rise.”

Rice mourns geophysicist, former college magister Dale Sawyer

Rice geophysicist Dale Sawyer, a respected scientist, dedicated educator and former magister of Will Rice and Sid Richardson colleges, died peacefully Sept. 15 after a long illness. He was 65.

Sawyer, professor emeritus of Earth, environmental and planetary sciences, joined Rice in 1988 and retired this year. He was well-known and esteemed around the world for his scientific leadership in marine geophysics, particularly his work on the origins of continental margins, and colleagues recalled he was beloved at Rice for his spirit, good humor and dedication to students and scholarship.

He and his wife, Elise, served as magisters of Will Rice from 1997-2002 and Sid Rich from 2009-2014.

“Dale was one of the kindest, most generous and caring people in the world, welcoming everyone with an enormous smile — and a bear hug if you were lucky,” said longtime research collaborator Julia Morgan, professor of Earth, environmental and planetary sciences. “And so eager to hear about your life, before he shared his own. He will be sorely missed by all.”

Sawyer was born in St. Louis, Missouri, traveled the world as a child and graduated from the International School of Bangkok before earning his bachelor’s degree in Earth science from Purdue University in 1976 and his doctorate in marine geophysics from the Massachusetts Institute of Technology in 1982.

He was a pioneer in the numerical modeling of crustal deformation and an expert in the acquisition and interpretation of active source seismic profiles. He frequently went to sea to collect seismic data aboard research ships, and because of his calm leadership skills and expertise he was tapped to serve as either chief scientist or co-chief scientist on half of the shipboard expeditions in which he participated.

“He ran research cruises from Chile to Iberia and elsewhere,” Morgan said. “His research changed our understanding of how continents evolve and also launched numerous students and colleagues on productive career paths.”

During their time as college magisters, he and Elise helped support more than 1,000 Rice undergraduates, and Morgan said Dale “was like a proud parent to every student in the college, excited about their interests and activities, saddened by their trials, and always there for them.”

After a fireworks celebration for the matriculation of Rice’s 100th class of freshmen in 2011, Sawyer, then magister at Sid Rich, told the Rice News, “It’s wonderful. At this point, all we see is their faces, and we have no idea what they’re going to be a year from now or four years from now. It’s just amazing to watch them grow and do things that they’re going to be proud of for the rest of their lives.”

Sawyer’s family said some of his favorite times at Rice were spent cheering the Sid Rich women to a powder puff football championship and the Will Rice Beer Bike team to a sweep, as well as helping to grow student-run theater. He also advised and mentored countless graduate students and postdocs and helped found the Department of Earth, Environmental and Planetary Sciences’ professional master’s program.

Dean of Undergraduates Bridget Gorman said, “Dale was a wonderful mentor to Rice students outside of the classroom. He had a big smile and wonderful laugh, and he cared deeply about students, their experiences at Rice and their development as scholars and citizens of the world. His passing is a true loss to our community.”

Sawyer’s teaching didn’t stop at Rice’s hedges. He spoke to grade school classes, worked with his students to create an introductory Earth sciences curriculum for middle and high school students that is still in use, and was frequently interviewed by news reporters seeking comment about the geological causes of earthquakes, tsunamis and other seismic events. In partnership with current and former students, Sawyer also co-taught continuing education courses for Houston-area high school science teachers that used ground-penetrating radar to locate graves in former slave cemeteries.

An Eagle Scout, Sawyer was also passionate about mentoring young people through the Boy Scouts of America. He was a Vigil Honor member of the Order of the Arrow, and though he served in many roles at the Sam Houston Area Council, he was most proud of helping to lead National Youth Leadership Training, a program that allowed him to mentor and coach hundreds of young men.

Sawyer’s travels took him to every continent, but Morgan said his heart was always at Rice.

“Rice University was always foremost in his mind: It was his life,” Morgan said. “There are few people I know who had so much loyalty and commitment to the university, to the department and most of all to the undergraduates who crossed his path.”

Sawyer was named outstanding faculty associate at Will Rice College from 1990-1997, was a distinguished alumnus of the Purdue Department of Earth, Atmospheric and Planetary Sciences, and was a member of the American Geophysical Union, the American Association of Petroleum Geologists, the Society of Exploration Geophysicists, the American Association for the Advancement of Science and Sigma Xi.

Sawyer was preceded in death by his daughter Kate and his father William. He is survived by Elise, his wife of 43 years; daughter Laura ’05, Sid Rich, and her wife Charnel de Villiers; son Matt ’12, Sid Rich, and his wife Kimberly Sawyer; mother Jane Ann Sawyer; sister Carole Bolin and numerous nieces and nephews.

 

In lieu of customary remembrances, the family requests that memorial gifts be made to the Sawyer New Student Award at Will Rice College or to the Houston Aphasia Recovery Center (HARC): Dale Sawyer Memorial Fund. Gifts to Rice may be made online at giving.rice.edu​ or mailed to Rice University, Office of Development MS-81, 6100 Main Street, Houston, TX, 77025. Gifts to HARC may be made online at ​www.harctx.org ​or mailed to 5005 Woodway Drive, Suite 110, Houston, TX, 77056.

About Jade Boyd

Jade Boyd is science editor and associate director of news and media relations in Rice University’s Office of Public Affairs.

The Passing of Dale Sawyer

Kirsten Siebach in science TV series ‘Life 2.0’

 

Kirsten Siebach and Scott Solomon in the debut episode of "Life 2.0"

Kirsten Siebach (left), assistant professor of Earth, environmental and planetary sciences, and Scott Solomon, associate teaching professor in biosciences, appear in the first episode of “Life 2.0,” a new television series that’s available for streaming and slated to debut on the air locally at 10 a.m. Saturday on Houston’s KRIV-TV (Fox 26). Siebach and Solomon were filmed at Rice in early 2019 for the episode, which explores the possibility of people colonizing Mars and the ways Mars might change humans who live there.

Small quake clusters can’t hide from AI

MIKE WILLIAMS – AUGUST 24, 2020

Rice researchers use deep learning to find signs were present before deadly Greenland landslide

Researchers at Rice University’s Brown School of Engineering are using data gathered before a deadly 2017 landslide in Greenland to show how deep learning may someday help predict seismic events like earthquakes and volcanic eruptions.

Seismic data collected before the massive landslide at a Greenland fjord shows the subtle signals of the impending event were there, but no human analyst could possibly have put the clues together in time to make a prediction. The resulting tsunami that devastated the village of Nuugaatsiaq killed four people and injured nine and washed 11 buildings into the sea.

An overview by the U.S. Geological Survey shows the location of the Nuugaatsiaq landslide (yellow star) relative to five broadband seismic stations (pink triangles) within 500 km of the landslide. Nuugaatsiaq (NUUG) was impacted by the resulting tsunami the reached a height of 300 feet at sea, though it was much lower before it reached the village. The inset shows the geometry of the fjords relative to the landslide and Nuugaatsiaq. (Source: USGS)

A study lead by former Rice visiting scholar Léonard Seydoux, now an assistant professor at the University of Grenoble-Alpes, employs techniques developed by Rice engineers and co-authors Maarten de Hoop and Richard Baraniuk. Their open-access report in Nature Communications shows how deep learning methods can process the overwhelming amount of data provided by seismic tools fast enough to predict events.

De Hoop, who specializes in mathematical analysis of inverse problems and deep learning in connection with Rice’s Department of Earth, Environmental and Planetary Sciences, said advances in artificial intelligence (AI) are well-suited to independently monitor large and growing amounts of seismic data. AI has the ability to identify clusters of events and detect background noise to make connections that human experts might not recognize due to biases in their models, not to mention sheer volume, he said.

Hours before the Nuugaatsiaq event, those small signals began to appear in data collected by a nearby seismic station. The researchers analyzed data from midnight on June 17, 2017, until one minute before the slide at 11:39 p.m. that released up to 51 million cubic meters of material.

The Rice algorithm revealed weak but repetitive rumblings — undetectable in raw seismic records — that began about nine hours before the event and accelerated over time, leading to the landslide.

“There was a precursor paper to this one by our co-author, Piero Poli at Grenoble, that studied the event without AI,” de Hoop said. “They discovered something in the data they thought we should look at, and because the area is isolated from a lot of other noise and tectonic activity, it was the purest data we could work with to try our ideas.”

De Hoop is continuing to test the algorithm to analyze volcanic activity in Costa Rica and is also involved with NASA’s InSight lander, which delivered a seismic detector to the surface of Mars nearly two years ago.

Constant monitoring that delivers such warnings in real time will save lives, de Hoop said.

Richard Baraniuk Credit: Jeff Fitlow/Rice University

 

Maarten de Hoop       Credit: Jeff Fitlow/Rice University

“People ask me if this study is significant — and yes, it is a major step forward — and then if we can predict earthquakes. We’re not quite ready to do that, but this direction is, I think, one of the most promising at the moment.”

When de Hoop joined Rice five years ago, he brought expertise in solving inverse problems that involve working backwards from data to find a cause. Baraniuk is a leading expert in machine learning and compressive sensing, which help extract useful data from sparse samples. Together, they’re a formidable team.

“The most exciting thing about this work is not the current result, but the fact that the approach represents a new research direction for machine learning as applied to geophysics,” Baraniuk said.

“I come from the mathematics of deep learning and Rich comes from signal processing, which are at opposite ends of the discipline,” de Hoop said. “But here we meet in the middle. And now we have a tremendous opportunity for Rice to build upon its expertise as a hub for seismologists to gather and put these pieces together. There’s just so much data now that it’s becoming impossible to handle any other way.”

De Hoop is helping to grow Rice’s reputation for seismic expertise with the Simons Foundation Math+X Symposia, which have already featured events on space exploration and mitigating natural hazards like volcanoes and earthquakes. A third event, dates to be announced, will study deep learning applications for solar giants and exoplanets.

A graph extracted by a novel Rice University algorithm shows waveforms from the cluster associated with precursors and aligned with respect to a reference waveform within the cluster. The data was from three seismograms collected over the course of the day before the Nuugaatsiaq landslide. (Source: Nature Communications)

Co-authors of the paper are Rice graduate student Randall Balestriero and Michel Campillo, a professor at Grenoble. Poli is a researcher at the French National Center for Scientific Research, Grenoble. De Hoop is the Simons Chair in Computational and Applied Mathematics and Earth Science and holds appointments in computational and applied mathematics, mathematics and Earth, environmental and planetary sciences at Rice. Baraniuk is the Victor E. Cameron Professor of Electrical and Computer Engineering and Computer Science at Rice and founder and director of OpenStax.

The research was supported by the European Research Council, the Multidisciplinary Institute in Artificial Intelligence at Grenoble-Alpes, the Simons Foundation, the Department of Energy, the National Science Foundation, the Air Force Office of Scientific Research, the Office of Naval Research and a Department of Defense Vannevar Bush Faculty Fellowship.

Rice researchers use InSight for deep Mars measurements

– AUGUST 5, 2020

Analysis of NASA lander seismograph data reveals boundaries from crust to core

Using data from NASA’s InSight Lander on Mars, Rice University seismologists have made the first direct measurements of three subsurface boundaries from the crust to the core of the red planet.

An artist's impression of Mars' inner structure.

An artist’s impression of Mars’ inner structure. The topmost layer is the crust, and beneath it is the mantle, which rests on a solid inner core. (Image courtesy of NASA/JPL-Caltech)

“Ultimately it may help us understand planetary formation,” said Alan Levander, co-author of a study available online this week in Geophysical Research Letters. While the thickness of Mars’ crust and the depth of its core have been calculated with a number of models, Levander said the InSight data allowed for the first direct measurements, which can be used to check models and ultimately to improve them.

EEPS graduate student Sizhuang Deng

EEPS graduate student Sizhuang Deng

“In the absence of plate tectonics on Mars, its early history is mostly preserved compared with Earth,” said study co-author Sizhuang Deng, a Rice graduate student. “The depth estimates of Martian seismic boundaries can provide indications to better understand its past as well as the formation and evolution of terrestrial planets in general.”

Finding clues about Mars’ interior and the processes that formed it are key goals for InSight, a robotic lander that touched down in November 2018. The probe’s dome-shaped seismometer allows scientists to listen to faint rumblings inside the planet, in much the way that a doctor might listen to a patient’s heartbeat with a stethoscope.

Alan Levander

Alan Levander

 

Seismometers measure vibrations from seismic waves. Like circular ripples that mark the spot where a pebble disturbed the surface of a pond, seismic waves flow through planets, marking the location and size of disturbances like meteor strikes or earthquakes, which are aptly called marsquakes on the red planet. InSight’s seismometer recorded more than 170 of these from February to September 2019.

Seismic waves are also subtly altered as they pass through different kinds of rock. Seismologists have studied the patterns in seismographic recordings on Earth for more than a century and can use them to map the location of oil and gas deposits and much deeper strata.

“The traditional way to investigate structures beneath Earth is to analyze earthquake signals using dense networks of seismic stations,” said Deng. “Mars is much less tectonically active, which means it will have far fewer marsquake events compared with Earth. Moreover, with only one seismic station on Mars, we cannot employ methods that rely on seismic networks.”

NASA's InSight lander deploying a domed cover on its seismometer

This Feb. 2, 2019 photo shows the robotic arm on NASA’s InSight lander deploying a domed cover that shield’s the lander’s seismometer from wind, dust and extreme temperatures. (Image courtesy of NASA/JPL-Caltech)

Levander, Rice’s Carey Croneis Professor of Earth, Environmental and Planetary Sciences, and Deng analyzed InSight’s 2019 seismology data using a technique called ambient noise autocorrelation. “It uses continuous noise data recorded by the single seismic station on Mars to extract pronounced reflection signals from seismic boundaries,” Deng said.

The first boundary Deng and Levander measured is the divide between Mars’ crust and mantle almost 22 miles (35 kilometers) beneath the lander.

The second is a transition zone within the mantle where magnesium iron silicates undergo a geochemical change. Above the zone, the elements form a mineral called olivine, and beneath it, heat and pressure compress them into a new mineral called wadsleyite. Known as the olivine-wadsleyite transition, this zone was found 690-727 miles (1,110-1,170 kilometers) beneath InSight.

“The temperature at the olivine-wadsleyite transition is an important key to building thermal models of Mars,” Deng said. “From the depth of the transition, we can easily calculate the pressure, and with that, we can derive the temperature.”

The third boundary he and Levander measured is the border between Mars’ mantle and its iron-rich core, which they found about 945-994 miles (1,520-1,600 kilometers) beneath the lander. Better understanding this boundary “can provide information about the planet’s development from both a chemical and thermal point of view,” Deng said.

The research was supported by Rice’s Department of Earth, Environmental and Planetary Sciences.

Future Texas hurricanes: Fast like Ike or slow like Harvey?

– JULY 6, 2020

Climate change will make fast-moving storms more likely in late 21st-century Texas

Climate change will intensify winds that steer hurricanes north over Texas in the final 25 years of this century, increasing the odds for fast-moving storms like 2008’s Ike compared with slow-movers like 2017’s Harvey, according to new research.

Hurricane Harvey as seen from the International Space Station on Aug. 28, 2017

Hurricane Harvey as seen from the International Space Station on Aug. 28, 2017. (Photo courtesy of Randy Bresnik/NASA)

The study published online July 3 in Nature Communications examined regional atmospheric wind patterns that are likely to exist over Texas from 2075-2100 as Earth’s climate changes due to increased greenhouse emissions.

The research began in Houston as Harvey deluged the city with 30-40 inches of rain over five days. Rice University researchers riding out the storm began collaborating with colleagues from Columbia University’s Lamont-Doherty Earth Observatory (LDEO) and Harvard University to explore whether climate change would increase the likelihood of slow-moving rainmakers like Harvey.

“We find that the probability of having strong northward steering winds will increase with climate change, meaning hurricanes over Texas will be more likely to move like Ike than Harvey,” said study lead author Pedram Hassanzadeh of Rice.

Pedram Hassanzadeh

Pedram Hassanzadeh

Harvey caused an estimated $125 billion in damage, matching 2005’s Katrina as the costliest hurricane in U.S. history. Ike was marked by coastal flooding and high winds that caused $38 billion damage across several states. It was the second-costliest U.S. hurricane at the time and has since moved to sixth. Ike struck Galveston around 2 a.m. Sept. 13, 2008, crossed Texas in less than one day and caused record power outages from Arkansas to Ohio on Sept. 14.

Hassanzadeh, a fluid dynamicist, atmospheric modeler and assistant professor of both mechanical engineering and Earth, environmental and planetary sciences, said the findings don’t suggest that slow-moving storms like Harvey won’t happen in late 21st century. Rather, they suggest that storms during the period will be more likely to be fast-moving than slow-moving. The study found the chances that a Texas hurricane will be fast-moving as opposed to slow-moving will rise by about 50% in the last quarter of the 21st century compared with the final quarter of the 20th century.

Suzana Camargo

Suzana Camargo

“These results are very interesting, given that a previous study that considered the Atlantic basin as a whole noticed a trend for slower-moving storms in the past 30 years,” said study co-author Suzana Camargo, LDEO’s Marie Tharp Lamont Research Professor. “By contrast, our study focused on changes at the end of the 21st century and shows that we need to consider much smaller regional scales, as their trends might differ from the average across much larger regions.”

Hassanzadeh said the researchers used more than a dozen different computer models to produce several hundred simulations and found that “all of them agreed on an increase in northward steering winds over Texas.”

Steering winds are strong currents in the lower 10 kilometers of the atmosphere that move hurricanes.

Map depicting total rainfall from 2017's Hurricane Harvey

Map depicting total rainfall from 2017’s Hurricane Harvey. (Image courtesy of NOAA)

“It doesn’t happen a lot, in studying the climate system, that you get such a robust regional signal in wind patterns,” he said.

Harvey was the first hurricane Hassanzadeh experienced. He’d moved to Houston the previous year and was stunned by the slow-motion destruction that played out as bayous, creeks and rivers in and around the city topped their banks.

“I was sitting at home watching, just looking at the rain when (study co-author) Laurence (Yeung) emailed a bunch of us, asking ‘What’s going on? Why is this thing not moving?’” Hassanzadeh recalled. “That got things going. People started replying. That’s the good thing about being surrounded by smart people. Laurence got us started, and things took off.”

Laurence Yeung

Laurence Yeung

Ebrahim Nabizadeh

Ebrahim Nabizadeh

Yeung, an atmospheric chemist, Hassanzadeh and two other Rice professors on the original email, atmospheric scientist Dan Cohan and flooding expert Phil Bedient, won one of the first grants from Rice’s Houston Engagement and Recovery Effort (HERE), a research fund Rice established in response to Harvey.

“Without that, we couldn’t have done this work,” Hassanzadeh said. The HERE grant allowed Rice co-author Ebrahim Nabizadeh, a graduate student in mechanical engineering, to work for several months, analyzing the first of hundreds of computer simulations based on large-scale climate models.

The day Harvey made landfall, Hassanzadeh also had reached out to Columbia’s Chia-Ying Lee, an expert in both tropical storms and climate downscaling, procedures that use known information at large scales to make projections at local scales. Lee and Camargo used information from the large-scale simulations to make a regional model that simulated storms’ tracks over Texas in a warming climate.

Chia-Ying Lee

Chia-Ying Lee

“One challenge of studying the impact of climate change on hurricanes at a regional level is the lack of data,” said Lee, a Lamont Assistant Research Professor at LDEO. “At Columbia University, we have developed a downscaling model that uses physics-based statistics to connect large-scale atmospheric conditions to the formation, movement and intensity of hurricanes. The model’s physical basis allowed us to account for the impact of climate change, and its statistical features allowed us to simulate a sufficient number of Texas storms.”

Hassanzadeh said, “Once we found that robust signal, where all the models agreed, we thought, ‘There should be a robust mechanism that’s causing this.’”

He reached out to tropical climate dynamicist Ding Ma of Harvard to get another perspective.

“We were able to show that changes in two important processes were joining forces and resulting in the strong signal from the models,” said Ma, a postdoctoral researcher in Earth and planetary sciences.

Ding Ma

Ding Ma

One of the processes was the Atlantic subtropical high, or Bermuda high, a semipermanent area of high pressure that forms over the Atlantic Ocean during the summer, and the other was the North American monsoon, an uptick in rainfall and thunderstorms over the southwestern U.S. and northwestern Mexico that typically occurs between July and September. Hassanzadeh said recent studies have shown that each of these are projected to change as Earth’s climate warms.

“The subtropical high is a clockwise circulation to the east that is projected to intensify and shift westward, producing more northward winds over Texas,” he said. “The North American monsoon, to the west, produces a clockwise circulation high in the troposphere. That circulation is expected to weaken, resulting in increased, high-level northward winds over Texas.”

Hassanzadeh said the increased northward winds from both east and west “gives you a strong reinforcing effect over the whole troposphere, up to about 10 kilometers, over Texas. This has important implications for the movement of future Texas hurricanes.”

Models showed that the effect extended into western Louisiana, but the picture became murkier as the researchers looked further east, he said.

Map depicting total rainfall from 2008's Hurricane Ike

Map depicting total rainfall from 2008’s Hurricane Ike. (Image by Hal Pierce/SSAI/NASA

“You don’t have the robust signal like you do over Texas,” Hassanzadeh said. “If you look at Florida, for instance, there’s a lot of variation in the models. This shows how important it is to conduct studies that focus on climate impacts in specific regions. If we had looked at all of North America, for example, and tried to average over the whole region, we would have missed this localized mechanism over Texas.”

Bedient is the Herman Brown Professor of Engineering and department chair of civil and environmental engineering and director of Rice’s Severe Storm Prediction, Education and Evacuation from Disasters Center. Cohan is an associate professor of civil and environmental engineering. Yeung is the Maurice Ewing Career Development Assistant Professor in Earth Systems Science in the Department of Earth, Environmental and Planetary Sciences.

The research was supported by the National Science Foundation, NASA, the Gulf Research Program of the National Academies of Sciences, Engineering and Medicine’s Early-Career Research Fellowship Program, Rice’s Houston Engagement and Recovery Effort Fund, Columbia’s Center for Climate and Life Fellows Program, the National Oceanic and Atmospheric Administration and the New York State Energy Research and Development Authority. Computational resources were provided by the National Science Foundation’s Extreme Science and Engineering Discovery Environment, the National Center for Atmospheric Research’s Computational and Information Systems Lab and Rice’s Center for Research Computing.