EPS Research Spotlight Archive


APR 2013 - Over the last three years, Burkhard Militzer's group has been working on understanding water at megabar pressures with ab initio computer simulations.

Over the last three years, Burkhard Militzer's group has been working on understanding water at megabar pressures with ab initio computer simulations. In the interiors of Uranus and Neptune (dashed lines in figure) where such pressures exist, water is predicted to occur in a superionic state where the oxgyen atoms remain stationary like in a solid while the hydrogen atoms diffuse throughout the crystal like a fluid. In the most recent article that appeared in the journal Physical Review Letters, postdoc Hugh Wilson, summer student Michael Wong, and Burkhard Militzer, show that, at 1.0±0.5 megabars, the oxygen sub-lattice in superionic water changes from a body-centered cubic lattice to an face-cented cubic lattice (inset). This transformation lead to a more efficient packing but also reduces the diffusion rate of the hydrogen atoms, which may have further implications for electronic conductivity and magnetic dynamo in Uranus and Neptune. This theorectical prediction is expected to be verified with laboratory experiments using shock wave and x-ray diffration techniques.
 

DEC 2012 - High pressure research unravels mysteries of nanomaterials

Over the last years Rudy Wenk’s group in the department has developed methods to investigate deformation of materials at ultrahigh pressures with diamond anvil cells. It was observed that brittle minerals such as olivine, perovskite and postperovskite become ductile above 20 GPa. This approach has been applied to study deformation mechanisms of rocks at deep Earth conditions and was applied to explain seismic anisotropy. A recent collaboration of Rudy and graduate student Jane Kanitpanyacharoen with scientists at the high pressure beamline 12.2.2. of the Advanced Light Source applied the technique to nanocrystalline metals which were generally thought not to be subject to dislocation glide. Yet at 37 GPa synchrotron X-ray diffraction images reveal that preferred orientation developed in nanocrystalline nickel, suggesting that also here pressure promotes dislocation activity. It highlights the university as a forum for interdisciplinary interaction, where methods developed by earth scientists to investigate the deep earth are used by engineers to shed light on puzzles of nanomaterials, one of the big issue in materials science. The novel results are reported in the recent issue of Science.

Reprint

 

JUL 2012 - Fertilizer use responsible for increase in nitrous oxide in atmosphere

In a report published in the April 1, 2012 issue of Nature Geoscience, EPS faculty member Kristie Boering (also Dept. of Chemistry), former EPS graduate student Sunyoung Park, and their co-authors measured the nitrogen and oxygen isotopes in nitrous oxide in air samples collected since 1978 at the Cape Grim Air Pollution Baseline Station (pictured) and in air trapped in snow in Antarctica dating back to 1940. The trends in the isotopes represent a "smoking gun" showing unequivocably that increasing fertilizer use is responsible for the dramatic rise in atmospheric nitrous oxide, which is a major greenhouse gas contributing to global climate change. 

Read Press Release from UC Berkeley at http://newscenter.berkeley.edu/2012/04/02/fertilizer-use-responsible-for-increase-in-nitrous-oxide-in-atmosphere/

Read the article at http://www.nature.com/ngeo/journal/v5/n4/abs/ngeo1421.html
 

OCT 2011 - Topographic evolution in glacial landscape of Fiordland, NZ

In a report published in the April 1, 2011 issue of Science, EPS faculty members David Shuster, Kurt Cuffey (also Dept. of Geography), former EPS graduate student Johnny Sanders, and Greg Balco of the Berkeley Geochronology Center, used apatite (U-Th)/He and 4He/3He thermochronometry to investigate topographic evolution in the archetypal glacial landscape of Fiordland, New Zealand.  They found that the topography near Milford Sound was clearly not in steady state over the last 2 million years, while erosion removed the entire pre-Pleistocene landscape.   Their data are best explained by up-valley propagation of erosion through the glacier-carved landscape during this time.  This scenario is consistent with a subglacial erosion rate dependent on ice sliding velocity, but not ice discharge. 

Read Press Release from UC Berkeley at http://newscenter.berkeley.edu/2011/03/31/novel-technique-reveals-how-glaciers-sculpted-their-valleys/

Read the full report at http://www.sciencemag.org/content/332/6025/84.full

 

DEC 2010 - Simulations predict water ice to become a metal at megabar pressures

Four high pressure phases of iceWater ice is one of the most prevalent substances in the solar system, with the majority of it existing at high pressures in the interiors of giant planets. The known phase diagram of water is extremely rich, with at least fifteen crystal phases observed experimentally. In our article in Physical Review Letters (see also cond-mat), Hugh Wilson and I (Burkhard Militzer) explore the phase diagram of water ice by means of ab initio computer simulations and predict two new phases to occur at megabar pressures. In the figure from top to bottom, you see

1) ice X the highest pressure phase seen in experiments, 
2) the Pbcm phase that was predicted with computer simulations in 1996,
3) our new Pbca phase that transforms out of the Pbcmphase via a phonon instability at 7.6 Mbar, and finally
4) our new Cmcm structure that is metallic and predicted to occur at 15.5 Mbar.

The known high pressure ice phases VII, VIII, X and Pbcmas well as our Pbca phase are all insulating and composed of two interpenetrating hydrogen bonded networks, but theCmcm structure is metallic and consists of corrugated sheets of H and O atoms. The H atoms are squeezed into octahedral positions between next-nearest O atoms while they occupy tetrahedral positions between nearest O atoms in the ice X, Pbcm, and Pbca phases.
 

OCT 2010 - spotlight

In a report published in the Sept. 24 issue of Science, current and former graduate students Lowell Miyagi, Waruntorn (Jane) Kanitpanyacharoen, Pamela Kearcher and Kanani Lee (Lowell and Kanani are now at Yale), working with faculty member Rudy Wenk, describe diamond anvil high pressure deformation experiments performed at ALS on the enigmatic mineral phase postperovskite MgSiO3. They observe strong mineral alignment due to intracrystalline dislocation movements that can be captured in inverse pole figures. This alignment, when applied to lowest mantle rheology, predicts fast S-waves to be polarized parallel to the core mantle boundary which is just what seismologists observe. Linking microscopic processes to macroscopic geodynamics provides new insight about the deep earth. Read Press Release from UC Berkeley.
 

SEP 2010 - Lithospheric layering in the North American craton

In a recent article published in the Aug. 26 issue of the journal Nature, BSL posdoc Huaiyu Yuan and faculty member Barbara Romanowicz report that the North American cratonic upper mantle is anisotropically stratified. The strong layering, inferred from rapid changes in the direction of azimuthal anisotropy with depth, reveals two distinct lithospheric layers (Chemical and Thermal layer in figure) throughout the stable part of the continent, and a relatively flat lithosphere-asthenosphere boundary (LAB) further separates the underlying asthenosphere. The findings tie together seismological, geochemical and geodynamical studies of the cratonic lithosphere in North America. Read press release from UC Berkeley and Science on msnbc.com.

 

MAR 2010 - Helium rain on Jupiter explains lack of neon in atmosphere

In a recent paper published in Physical Review Letters, EPS postdoc Hugh Wilson and faculty member  Burkhard Militzer report calculations showing that the large deficiency of neon in the atmosphere of Jupiter observed by the Galileo probe can be explained by the existence of a hydrogen-helium immiscibility layer deep within the planet. The new calculations show that neon atoms are absorbed into helium-rich droplets which then rain deeper into the planet's interior, leading to an atmosphere that is depleted of both helium and neon.  Read commentary by J. Fortney, press release from UC Berkeley, helium rain forcast on the Discovery Channel, and LA Times report about helium rain washing away neon.
 

JAN 2010 - Tremor-tide correlations on the deep San Andreas fault

Example one-day tremor time series with superimposed tidal stressesEPS graduate student Amanda Thomas, BSL Researcher Bob Nadeau and EPS faculty member Roland Bürgmann identify a robust correlation between extremely small, tidally induced shear stress parallel to the San Andreas fault and non-volcanic tremor activity near Parkfield, California. In their recently published article in Nature (Reprint), they suggest that this tremor represents shear failure on a critically stressed fault in the presence of near-lithostatic pore pressure. UC Berkeley News Release.
 

JAN 2009 - Research Spotlight

In their recently published article in Nature, EPS graduate student Alexander (Zan) Stine, Harvard fauculty member Peter Huybers, and EPS faculty member Inez Fung have found a shift towards earlier seasonal transitions in the temperature record over extratropical land in the last 57 years. This shift is anomolous when compared to the variability seen in the preceeding 100 years, and is not predicted by any of the model-based simulations of 20th century climate reported by the IPCC. (reprint)
Zan Stine discusses this work on Nature's podcast.
In the Press

 

AUG 2008 - Formation of Box Canyon, Idaho, by Megaflood: Implications for Seepage Erosion on Earth and Mars

EPS graduate students Michael Lamb and Sarah Aciego and EPS faculty members Bill Dietrich, Michael Manga and Don DePaolo have found new evidence that amphitheater-headed canyons on Earth and Mars might be carved by catastrophic floods rather than slow erosion by seepage erosion.  Studying Box Canyon Idaho, which has morphologic attributes long inferred to result from gradual erosion by spring water, the team reported in the journal Science (reprint) that the canyon was instead carved during a megaflood about 45 thousand years ago. Press coverage.
 

MAY 2008 - Pinpointing the dinosaurs' demise

EPS faculty member Paul Renne and colleagues at the Berkeley Geochronology Center, the Free University of Amsterdam, and Utrecht University, are fine-tuning geochronology to unprecedented levels of accuracy. By calibrating the uniquely versatile 40Ar/39Ar radioisotopic dating method with climate proxy signals tracking Earths orbital cycles, the team reported a ten-fold increase in accuracy. As an illustration of the consequences of their study, reported in Science (reprint), the age of the Cretaceous/Tertiary boundary, and the extinction of the dinosaurs, has been adjusted by almost 500,000 years to 65.95 Ma. UC Berkeley news release.
 

APR 2008 - New source of iron in the Western North Pacific

EPS faculty member Jim Bishop and Phoebe Lam, former graduate student and now an assistant scientist at Woods Hole Oceanographic Institution, are challenging the theory that almost all iron for fertilizing oceanic plankton blooms comes from wind-blow dust. In a recent issue of Geophysical Research Letters (reprint) they show that the key source of iron in the Western North Pacific is not dust, but the volcanic shelf sediments of the Kuril - Kamchatka island arc system. Understanding the origins, transport mechanisms and fate of naturally occurring iron in high-nutrient, low-chlorophyll surface waters is important in climate change calculations.
 

AUG 2007 - Post-Perovskite and D'' Anisotropy

In a recent issue of Science (reprint) researchers from Berkeley (Miller fellows Sebastien Merkel and Sergio Speziale, graduate student Lowell Miyagi and EPS faculty Rudy Wenk), Arizona State University, Princeton and the Advanced Photon Source at Argonne report on experimental deformation of the mineral phase postperovskite MgSiO3 with diamond anvil cells at pressures of 150 GPa. This phase is supposed to constitute the D” layer in the earth, just above the liquid core boundary. Using information about deformation mechanisms derived from the experiments the team then model the evolution of anisotropy in the deep earth that seismologists have observed.
 

JUL 2007 - Extracellular Proteins Limit the Dispersal of Biogenic Nanoparticles

In their recently published paper in Science (reprint), recent EPS Ph.D. graduate John Moreau and Prof. Jill Banfield, along with colleagues from Lawrence Berkeley and Lawrence Livermore National Labs, demonstrated the presence of extracellular biofilm proteins inside bacterially-formed aggregates of nanocrystalline zinc-sulfide (orange and yellow features in image). These proteins promoted the rapid aggregation of sulfide nanoparticles formed by bacterial sulfate reduction in an abandoned flooded mine, and thereby restricted the dispersal of contaminant metals such as zinc, arsenic and selenium. In nature, metal-binding proteins associated with sulfate-reducing bacteria or biofilm formation may serve to inhibit the mobility of nanoparticulate or colloidal toxic metals away from their source.
 

JUN 2007 - Evidence for an ancient martian ocean in the topography of deformed shorelines

In their recently published paper in Nature (reprint), Taylor Perron, Jerry Mitrovica, Michael Manga, Isamu Matsuyama and Mark Richards argue that there were once oceans on Mars, but that Mars has tipped over since they dried up. The northern plains are ringed by surface features that look like relic shorelines. However, long-wavelength trends in their elevation argue against the shoreline hypothesis. In this new study it is shown that polar wander can explain the shoreline deformation.
 

MAY 2007 - Study reveals two layers of seismic anisotropy beneath North America

In their recently published paper in Nature (reprint), Barbara Romanowicz and Federica Marone present their study of seismic anisotropy beneath the North American continent. Seismic anisotropy provides information about mineral orientations, which, in turn, can be related to flow in the mantle. Their study shows evidence for two layers of anisotropy. At asthenospheric depths, the fast axis is sub-parallel to the plate motion, confirming the presence of shear related to current tectonic processes, whereas within the lithosphere, the orientation is significantly different, indicating that anisotropy at these shallower depths was 'frozen-in' long ago.
 

FEB 2007 - Genomic sequencing of acid mine drainage biofilms reveals unusual microorganisms involved in geochemical cycling

In their recently published Science paper (reprint) Brett Baker and Jill Banfield and prior members of the Banfield group (Gene Tyson, Eric Allen, Judith Flanagan, Phil Hugenholtz), in collaboration with Rick Webb (Univeristy of Queensland), describe the discovery microbes on a novel branch on the tree of life. The archaeal organisms grow within acid mine drainage microbial communities that play a key role in metal sulfide mineral dissolution and acid mine drainage formation. These groups, named ARMAN, were overlooked by conventional microbiological methods (PCR and culturing). Surprisingly, these cells appear to be among the smallest yet described. The study shows how community genomic analyses can detect new lineages of organisms and facilitate their characterization, enhancing our understanding of the role of microorganisms in important geochemical processes.
 

SEP 2006 - The Keck HydroWatch Center is launched

Professors Inez Fung, Ronald Cohen, Donald DePaolo, William Dietrich and James Kirchner of the Dept. of Earth and Planetary Science have formed the Keck HydroWatch Center with Professor David Culler of the Dept. of Electrical Engineering and Computer Science. The new center will dramatically expand the observations of all aspects of the water cycle by developing cost-effective, rapid-response, and accurate sensors and techniques to monitor water quality, quantity, and pathways.
 

FEB 2006 - Plastic deformation of MgGeO3 post-perovskite at lower mantle pressures

In their recent Science paper (reprint), S. Merkel, A. Kubo, L. Miyagi, S. Speziale, T. Duffy, H.-k. Mao, and Rudy Wenk investigate the deformation behavior of germanate post-perovskite at pressures beyond 100 GPa. From the pattern of preferred orientation they determine that slip (100) and (110) slip is dominant. With this experimental information they model seismic anisotropy at the core-mantle boundary and suggest that perovskite contributes about 4% to shear wave splitting in D", with an oblique polarization.
 

JAN 2006 - The search for a topographic signature of life

In their paper recently published in Nature (reprint) Bill Dietrich and Taylor Perron investigate the influence of biota on the processes controlling landscape form and evolution. They find that while the signatures of life are present at all scales, there is no single landform that uniquely reflects the presence of life. Listen to the Nature Podcast (segment starts at 16:30).
 

NOV 2005 - The deterministic nature of earthquake rupture

In a paper recently published in Nature (reprint) Erik Olson and Richard Allen report a scaling relation between the frequency content of the first few seconds of energy radiated from an earthquake rupture and its magnitude. These characteristics can be used to estimate the magnitude before the rupture is complete and provide a basis for an earthquake alarm system.
 

MAY 2005 - PKJKP seismic phase detection and identification

In a paper recently published in Science (reprint), graduate student Aimin Cao, Professor Barbara Romanowicz and collaborator Nozumu Takeuchi report on the to-date most clear detection and identification of PKJKP, the elusive seismic phase that travels as a shear wave through the inner core.