EPS Research Spotlight Archive
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.