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.

Jeffrey Nittrouer and Hongbo Ma -Yellow River research highlighted in China Daily

http://usa.chinadaily.com.cn/world/2017-05/23/content_29466587.htm

 

Audrey Odwuor, an Earth Science graduating senior, receives the 2017 Dr. Mae C. Jemison Award for Academic Achievement and Public Service

Deep Subduction of Organic Carbon Helped Atmospheric Oxygen Rise

Study: Early organic carbon got deep burial in mantle

Petrology experiments support tectonic role in Earth’s ‘great oxidation event’

Rice University petrologists who recreated hot, high-pressure conditions from 60 miles below Earth’s surface have found a new clue about a crucial event in the planet’s deep past.

Earth's atmosphere, as seen in 2003 from the International Space Station

Earth’s atmosphere, as seen in 2003 from the International Space Station, hasn’t always contained large amounts of oxygen. Petrologists from Rice University and the Carnegie Institution recreated hot, high-pressure conditions from 60 miles below Earth’s surface in search of new clues about the “great oxidation event” that added large amounts of oxygen to the atmosphere around 2.4 billion years ago. (Photo courtesy of ISS Expedition 7 Crew, EOL, NASA)

Their study describes how fossilized carbon — the remains of Earth’s earliest single-celled creatures — could have been subsumed and locked deep in Earth’s interior starting around 2.4 billion years ago — a time when atmospheric oxygen rose dramatically. The paper appears online this week in the journal Nature Geoscience.

“It’s an interesting concept, but in order for complex life to evolve, the earliest form of life needed to be deeply buried in the planet’s mantle,” said Rajdeep Dasgupta, a professor of Earth science at Rice. “The mechanism for that burial comes in two parts. First, you need some form of plate tectonics, a mechanism to carry the carbon remains of early life-forms back into Earth. Second, you need the correct geochemistry so that organic carbon can be carried deeply into Earth’s interior and thereby removed from the surface environment for a long time.”

At issue is what caused the “great oxidation event,” a steep increase in atmospheric oxygen that is well-documented in countless ancient rocks. The event is so well-known to geologists that they often simply refer to it as the “GOE.” But despite this familiarity, there’s no scientific consensus about what caused the GOE. For example, scientists know Earth’s earliest known life, single-celled cyanobacteria, drew down carbon dioxide from the atmosphere and released oxygen. But the appearance of early life has been pushed further and further into the past with recent fossil discoveries, and scientists now know that cyanobacteria were prevalent at least 500 million years before the GOE.

Megan Duncan

Megan Duncan (Photo by Jeff Fitlow/Rice University)

“Cyanobacteria may have played a role, but the GOE was so dramatic — oxygen concentration increased as much as 10,000 times — that cyanobacteria by themselves could not account for it,” said lead co-author Megan Duncan, who conducted the research for her Ph.D. dissertation at Rice. “There also has to be a mechanism to remove a significant amount of reduced carbon from the biosphere, and thereby shift the relative concentration of oxygen within the system,” she said.

Removing carbon without removing oxygen requires special circumstances because the two elements are prone to bind with one another. They form one of the key components of the atmosphere — carbon dioxide — as well as all types of carbonate rocks.

Dasgupta and Duncan found that the chemical composition of the “silicate melt” — subducting crustal rock that melts and rises back to the surface through volcanic eruptions — plays a crucial role in determining whether fossilized organic carbon, or graphite, sinks into the mantle or rises back to the surface through volcanism.

Schematic depiction of the efficient deep subduction of organic carbon

This schematic depicts the efficient deep subduction of organic (reduced) carbon, a process that could have locked significant amounts of carbon in Earth’s mantle and resulted in a higher percentage of atmospheric oxygen. Based on new high-pressure, high-temperature experiments, Rice University petrologists argue that the long-term sequestration of organic carbon from this process began as early as 2.5 billion years ago and helped bring about a well-known buildup of oxygen in Earth’s atmosphere — the “Great Oxidation Event” — about 2.4 billion years ago. (Image courtesy of R. Dasgupta/Rice University)

Duncan, now a research scientist at the Carnegie Institution in Washington, D.C., said the study is the first to examine the graphite-carrying capacity of a type of melt known as rhyolite, which is commonly produced deep in the mantle and carries significant amounts of carbon to the volcanoes. She said the graphite-carrying capacity of rhyolitic rock is crucial because if graphite is prone to hitching a ride back to the surface via extraction of rhyolitic melt, it would not have been buried in sufficient quantities to account for the GOE.

“Silicate composition plays an important role,” she said. “Scientists have previously looked at carbon-carrying capacities in compositions that were much more magnesium-rich and silicon-poor. But the compositions of these rhyolitic melts are high in silicon and aluminum and have very little calcium, magnesium and iron. That matters because calcium and magnesium are cations, and they change the amount of carbon you can dissolve.”

Dasgupta and Duncan found that rhyolitic melts could dissolve very little graphite, even when very hot.

“That was one of our motivations,” said Dasgupta, professor of Earth science. “If subduction zones in the past were very hot and produced a substantial amount of melt, could they completely destabilize organic carbon and release it back to the surface?

“What we showed was that even at very, very high temperatures, not much of this graphitic carbon dissolves in the melt,” he said. “So even though the temperature is high and you produce a lot of melt, this organic carbon is not very soluble in that melt, and the carbon gets buried in the mantle as a result.

Rajdeep Dasgupta

Rajdeep Dasgupta (Photo by Jeff Fitlow/Rice University)

“What is neat is that with the onset and the expected tempo of crustal burial into the deep mantle starting just prior to the GOE, and with our experimental data on the efficiency of deep burial of reduced carbon, we could model the expected rise of atmospheric oxygen across the GOE,” Dasgupta said.

The research supports the findings of a 2016 paper by fellow Rice petrologist Cin-Ty Lee and colleagues that suggested that plate tectonics, continent formation and the appearance of early life were key factors in the development of an oxygen-rich atmosphere on Earth.

Duncan, who increasingly focuses on exoplanetary systems, said the research could provide important clues about what scientists should look for when evaluating which exoplanets could support life.

The research is supported by the National Science Foundation and the Deep Carbon Observatory.

About Jade Boyd

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

 

Cin-Ty Lee- 2017 Guggenheim Fellow

Rice’s Cin-Ty Lee wins Guggenheim Fellowship

Earth scientist will study how and when continents emerged from oceans

Rice University Earth scientist Cin-Ty Lee has won a prestigious Guggenheim Fellowship to investigate how and when continents emerged from the oceans and the effect of their emergence on the evolution of whole-Earth cycling of life-giving nutrients.

Lee is one of 173 scholars, artists and scientists — and the only Earth scientist — chosen as 2017 Guggenheim Fellows. The fellows represent 49 disciplines and 64 academic institutions and were chosen from nearly 3,000 applicants. Funded by the John Simon Guggenheim Memorial Foundation, the fellowships are awarded on the basis of achievements and exceptional promise to allow scholars to pursue their work with creative freedom.

Lee joined Rice in 2002 and is a professor and chair of the Department of Earth Science. He studies the compositions of rocks to reconstruct how Earth’s interior, surface, atmosphere and life have evolved over time. Specifically, his interests lie in understanding how mountains and continents form, how Earth’s deep interior has differentiated and how deep-Earth processes modulate long-term climate and Earth’s habitability.In addition to researching the emergence and impact of continents, Lee will use the Guggenheim funding to explore crystal growth and kinetics in magmatic and hydrothermal conditions.

Lee has a B.A. from the University of California, Berkeley and a Ph.D. from Harvard University. He has published more than 100 papers on a wide range of topics, including whole-Earth carbon cycling, the rise of atmospheric oxygen, the formation of ore deposits, coupling between magmatism and erosion, the temperature of Earth’s mantle and the origin of granites. He is a fellow of the Mineralogical Society of America and the Geological Society of America and has been awarded the Kuno Medal from the American Geophysical Union, the Clarke Medal from the Geochemical Society, the Donath Medal from the Geological Society of America and a Packard Fellowship.

Lee is also a world-renowned field ornithologist who spends much of his spare time painting birds and traveling the world in search of birds. He has published numerous articles on field identification of such difficult complexes as Arctic and Pacific loons, female orioles, American and Siberian pipits and dowitchers. He is currently working on a new guide to the identification of Empidonax flycatchers. He donates his paintings, teaches courses and leads field trips to benefit conservation-oriented nonprofit organizations and local schools.

Guggenheim Fellowships have been awarded annually since 1925. Each fellow is awarded a grant to help provide them with blocks of time in which they can work with as much creative freedom as possible. Grants have no special conditions attached and fellows may spend their grant funds in any manner they deem necessary to do their work.

see more : Rice’s Cin-Ty Lee wins Guggenheim Fellowship

Sarah Gerenday receives HGS Undergraduate Scholarship

The Houston Geological Society Undergraduate Scholarship Foundation have chosen Sarah Gerenday to receive a scholarship for the 2016-2017 academic year. The scholarship goal is to provide financial support for applicants in their endeavor towards a career in geoscience.

Sarah Gerenday is an undergraduate Senior with diverse interests and talents ranging from donating time to social programs in support of medical research and minority student recruiting, to international choir residency at St. Mary’s Cathedral in Edinburgh.

In the summer of 2015, Sarah was granted the the opportunity to participate in a Department of Energy sponsored Science Undergraduate Laboratory Internship at Argonne National Lab’s Applied Geoscience and Environmental Management section. That effort will support Sarah’s goal to continue with graduate research focused on the safety and effectiveness of combined geological and industrial endeavors, using geologic knowledge to develop efficient plans that minimize environmental impact.

Currently, Sarah is working on a senior honors thesis that studies the physical and geochemical history of peridotite zenoliths from kimberlites in the Kaapvaall craton in South Africa.

The HGS Foundation Trustees have invited Sarah and a faculty representative to attend the February 13th dinner meeting where they will honor all the scholarship winners.

Dr. Albert Bally awarded a Doctor Honoris Causa from the University of Fribourg (Switzerland)