Sarah Slotznick (former Miller postdoc now an Assistant Professor Dartmouth) had her research with EPS Professor Nick Swanson-Hysell on iron speciation in ancient rocks featured as a Research Spotlight in EOS (https://eos.org/research-spotlights/review-of-go-to-iron-analysis-method...). The spotlight focuses on research recently published in an article entitled: Unraveling the Mineralogical Complexity of Sediment Iron Speciation Using Sequential Extractions (https://doi.org/10.1029/2019GC008666).
Text of the research spotlight:
Iron is the most abundant transition metal in Earth’s crust—occurring in a wide variety of minerals and in multiple oxidation states, mainly ferrous, or +2, and ferric, or +3—and its presence in different forms in rocks can tell vivid stories about ancient environmental conditions on the planet, such as past nutrient cycling, geologic activity, and oxygen contents.
In recent decades, scientists have probed iron content and speciation in rock samples with a laboratory technique that uses different chemicals to sequentially dissolve, or extract, specific types of iron. First, acetate is used to dissolve iron in carbonates, then hydroxylamine hydrochloride is used for easily reducible oxyhydroxides, then dithionite for ferric iron (oxyhydr)oxides like goethite, and finally, oxalate for magnetite.
In a new study, Slotznick et al. report on magnetic experiments and X-ray diffraction measurements of samples dating from 1.5 billion years ago in the Precambrian up through the Holocene to check just how accurate the assignment of minerals associated with the sequential extraction process actually is. They found that for some steps, especially the one involving dithionite, the technique worked as expected; in other words, dithionite dissolved the target ferric iron (oxyhydr)oxides efficiently while leaving other forms of iron untouched. For other steps, though—especially the final step in which oxalate is used to dissolve magnetite—the researchers discovered that the process did not work as expected. They suggest that in this last step, oxalate was dissolving iron bound in clays rather than just iron in magnetite.
The researchers say their data indicate that the extraction technique is more complex than previously assumed. Overall, the magnetic and X-ray diffraction analyses suggested that dissolution of iron phases was more gradual than realized, with undissolved portions of minerals from previous steps lingering and with slow dissolution of iron outside the intended targets. Part of the complication, the scientists say, is that rock samples can be extremely heterogeneous and variables like composition, grain size, and crystallinity can create differences that affect how iron dissolves.
The team’s analysis of a large data compilation highlighted that Precambrian sedimentary rocks contain more iron that is dissolved by oxalate (and thus they potentially contain more of certain iron-bearing clays) than Phanerozoic sedimentary rocks. The researchers say this observation suggests that a significant shift in iron cycling occurred between these two time periods. (Geochemistry, Geophysics, Geosystems, https://doi.org/10.1029/2019GC008666, 2020)
Citation: Shultz, D. (2020), Review of go-to iron analysis method reveals its pros and cons, Eos, 101, https://doi.org/10.1029/2020EO141919. Published on 27 March 2020. CC BY-NC-ND 3.0
Doug Hemingway (former Miller postdoc now at Carnegie) published research with Max Rudolph (UC Davis) and EPS Professor Michael Manga about striping effect on Saturn's moon. Their paper, Cascading parallel fractures on Enceladus, offers an explanation of the unique stripes present on the south pole of Enceladus.
EPS Professor Imke de Pater and graduate student Chris Moeckel study the atmospheric mechanisms that create eruptions of ammonia on Jupiter. The ammonia plumes affect the visible color banding of Jupiter's atmosphere as the eruptions of white gas displace the other darker, typically brown, lower-level clouds.
Click here for the full article published in Astronomical Journal, "First Alma Millimeter Wavelength Maps of Jupiter, with a Multi-Wavelength Study of Convection".
Check out here for an interview Imke de Pater on Space .com, "Ammonia Storms on Jupiter Are Messing Up Its Picture-Perfect Cloud Bands".
Go here for an interview with Chris Moeckel in The Daily Californian about this research, "UC Berkeley study finds ammonia plumes changing Jupiter’s atmosphere".
Image: Scientists on board the R/V Thomas G. Thompson recover a seismometer that had been recording earthquakes on the seafloor off the Pacific Northwest coast. Scientists used this information to confirm the presence of a tear in the Juan de Fuca tectonic plate under central Oregon. (Photograph by William Hawley)
A hole in a subducted plate, in the mantle beneath North America, may cause volcanism and earthquakes on the surface of the Earth. Volcanism on the surface of North America appears to have been spatially coincident with a known zone of weakness on the slab for the last ~17 million years. We suggest that this hole is caused by tearing along the zone of weakness, a feature that is created when the plate is formed at the ridge. The tearing not only causes volcanism on North America but also causes deformation of the not‐yet‐subducted sections of the oceanic plate offshore. This tearing may eventually cause the plate to fragment, and what is left of the small pieces of the plate will attach to other plates nearby.
William Hawley (EPS graduate student) and Richard Allen (EPS Professor, BSL Director) present a tomographic model of the Pacific Northwest from onshore and offshore seismic data that reveals a hole in the subducted Juan de Fuca plate.
For a write-up in National Geographic about this research, click here.
Click here for the full article, The Fragmented Death of the Farallon Plate, published in Geophysical Research Letters.
Robert Sanders, Media relations|June 24, 2019
You might expect that plants hoping to thrive in California’s boom-or-bust rain cycle would choose to set down roots in a place that can store lots of water underground to last through drought years.
But some of the most successful plant communities in the state — and probably in Mediterranean climates worldwide — that are characterized by wet winters and dry summers have taken a different approach. They’ve learned to thrive in areas with a below-ground water storage capacity barely large enough to hold the water that falls even in lean years.
Surprisingly, these plants do well in both low-water and rainy years precisely because the soil and weathered rock below ground store so little water relative to the rain delivered.
“The key point from our study is that, in many sites on the North Coast, the storage capacity is small relative to how much it rains,” said Jesse Hahm, a graduate student at the University of California, Berkeley, and one of two first authors of the study. “Because the capacity for the subsurface to store water over the wet season is small, it still rains enough, even in the dry years, to replenish the water supply. The limited below-ground storage capacity is the key mechanism that decouples the plants and how much water availability they have in the summer from big swings in winter rainfall.”
As a result, these plants are much more resilient in drought years, as evidenced by California’s relatively unscathed North Coast during recent droughts that killed hundreds of millions of trees in the Sierra Nevada.
“Because the subsurface water gets replenished even in drought years, in the summer these plants feel the same amount of water supply below ground, no matter how much rain fell during the winter,” Hahm said. “They don’t really know if it rained a lot or a little, because they have the same amount of water stored below ground each summer.”
On the flip side, plants growing today on ground that can soak up as much water as the winter rains can provide are hosting plants that will have to deal with the state’s increasingly drier climate, putting them at risk as the climate changes. This may be a problem for Sierra Nevada plant communities that are relying less on a persistent snowpack and increasingly on stored subsurface water to last through the dry summer.
Hahm and David Dralle, the other first author and a former Berkeley graduate student who is an assistant professor at Sacramento State University, describe their findings, along with their colleagues, in a paper recently accepted by the journal Geophysical Research Letters and now posted online.
While most people think plants rely only on water stored in the topsoil, Berkeley’s William Dietrich, professor of earth and planetary science, and recent graduate Daniella Rempe, an assistant professor at the University of Texas, Austin, recently discovered that water stored in fractured and weathered rock underneath the soil plays an equal or greater role. What Dietrich and Rempe call “rock moisture” can amount to a significant proportion of what plants rely on annually.
A major implication of the new study, Dietrich says, is that global climate models need to incorporate rock moisture into their calculations to accurately represent and predict the impacts of drought or heavy rainfall. In recent years, drought- or heat-killed trees have fueled catastrophic wildfires in California, Spain, Greece, Australia and many regions with a dry, Mediterranean climate.
“Understanding how water is stored deep within the weathered bedrock and how variations in that water supply and in rainfall affect plant water supply in that zone is extremely important in a seasonally dry climate,” Hahm said.
In their study, the researchers looked at 26 sites statewide. All were below the snow belt, so that winter rain stored below ground was the dominant source of water for the plants during the summer dry season. Using rainfall data and U.S. Geological Survey stream flow data to calculate the amount of water stored annually underground, they were able to assess the below-ground storage capacity of the soil and the weathered rock.
Of the 26 sites, only seven — all in the Northern Coast Ranges — had limited subsurface water storage capacity and fared well during the state’s recent protracted drought, between 2011 and 2016. These sites ranged from grass and oak savanna and chaparral to dense Douglas fir forests, but all were characterized by low subsurface storage relative to average annual rainfall in the area, which tends to be high. The excess water that the subsurface couldn’t store in the winter ran through the soil and fractured bedrock and ended up in the streams.
The other sites, including most sites in Southern California, suffered in the drought, with vegetation die-offs and less healthy, less green plants. All were characterized by below-ground storage that is sufficient to sop up most of the rainfall that falls yearly, but that had been left depleted in drought years.
Using satellite images to gauge the productivity and health of the vegetation at each site, the researchers concluded that the sites with high relative storage capacity were the ones that varied the most between wet and dry years in how green the plants were. Sites with low below-ground storage capacity relative to average annual precipitation fared better, remaining similarly green and healthy in drought years and wet years alike.
Hahm noted that many plants in the Sierra Nevada rely on the snowpack to quench their thirst during typical rainless summers. But as temperatures rise with global warming, winter precipitation will increasingly occur as rain.
“In a way, this is a glimpse into the future,” Hahm said. “As the climate warms, and as the snowline elevation increases in these mountain ranges, more and more places will switch from being reliant on snowpack to being reliant on water stored in the subsurface. Understanding how this storage capacity limitation will impact plants across the state in high montane areas needs to be explored more.”
The insights about rock moisture emerged from a long-term project at the Angelo Coast Range Reserve in Northern California, part of the UC Natural Reserve System, where scientists at the Eel River Critical Zone Observatory followed water from the sky through vegetation, soil and rock into the streams and back up into the atmosphere via evaporation and transpiration to chart the life cycle of water in the environment. Primary funding for the observatory, which Dietrich directs, comes from the National Science Foundation (EAR 1331940).
Other co-authors of the study are graduate student Alexander Bryk and Todd Dawson, professor of integrative biology, both from Berkeley, and Sally Thompson of the University of Western Australia.
- Low subsurface water storage capacity relative to annual rainfall decouples Mediterranean plant productivity and water use from rainfall variability (Geophysical Research Letters)
- Lithologically Controlled Subsurface Critical Zone Thickness and Water Storage Capacity Determine Regional Plant Community Composition (Water Resources Research)
- Hidden ‘rock moisture’ may be key to tree survival during drought (February 2018)
In a new paper in the journal Proceedings of the National Academy of Sciences, paleontologist Robert DePalma and his colleagues, including Walter Alvarez a Professor of the Graduate School and Professor Mark Richards from University of California, Berkeley Earth and Planetary Sciences, describe the site, dubbed Tanis, and the evidence connecting it with the asteroid or comet strike off Mexico’s Yucatan Peninsula 66 million years ago. That impact created a huge crater, called Chicxulub, in the ocean floor and sent vaporized rock and cubic miles of asteroid dust into the atmosphere. The cloud eventually enveloped Earth, setting the stage for Earth’s last mass extinction.
“It’s like a museum of the end of the Cretaceous in a layer a meter-and-a-half thick,” said Mark Richards, a UC Berkeley professor emeritus of earth and planetary science who is now provost and professor of earth and space sciences at the University of Washington.
Richards and Walter Alvarez, a UC Berkeley Professor of the Graduate School who 40 years ago first hypothesized that a comet or asteroid impact caused the mass extinction, were called in by DePalma and Dutch scientist Jan Smit to consult on the rain of glass beads and the tsunami-like waves that buried and preserved the fish. The beads, called tektites, formed in the atmosphere from rock melted by the impact.
Read the full article here
(Graphic courtesy of Robert DePalma)
Edwards Lab heads to sea to collect particulate lipid samples from the San Pedro Basin, halfway between Long Beach and Catalina Island. These samples will be used to study the microbial biology of the area and their impacts on ocean biogeochemistry. Learn more at the lab's website, https://www.bethanieedwardslab.com
Photos courtesy of Will Kumler, Edwards Lab Manager.
CIDER is a yearly interdisciplinary research incubator made possible by @BerkeleySeismo's Dr. Barbara Romanowicz, where Earth dynamicists collaborate on interdisciplinary new ideas like this:
Explore EPS summer classes! UC Berkeley is an open university during summer please review our schedule here.
This summer, you can gain an overview of the water supply that controls our natural ecosystems and human civilization in EPS 3 "The Water Planet."
Ever wonder what are our planets made of? Why do they orbit the sun the way they do? Why do some bizarre moons have oceans, volcanoes and ice? You can take a tour of the mysteries and inner workings of our solar system in EPS W12 "The Planets", an online course offering.
A very popular course, EPS 20 "Earthquakes in Your Backyard" gives students an introduction to seismology and geological tectonics, with particular emphasis on the situation in California.
EPS N82 "Introduction to Oceans" teaches students the geology, physics, chemistry and biology of the world oceans. The course will apply oceanographic sciences to human problems to explore topics such as energy from the sea, marine pollution, food from the sea, and climate change.
For information on these topics and other departmental course offerings, please click here.
UC Berkeley News uploaded a new video onto YouTube of Earth and Planetary Science Professor Jim Bishop explaining how he and his research team are utilizing robots to collect data on climate change.
Check out the USS Oceanus’ blog on the Lawrence Berkeley National Laboratory site: http://oceanbots.lbl.gov/.
Sarah Yang continues to update the research team's blog, so video interviews from scientists and crew will be posted on the site periodically. The scientists were very fortunate to have Sarah Yang to be at sea with them, as she was able to collect some cool videos and other materials. Remember, scientists were at sea for 10 days with ocean-going robots to measure carbon dioxide in the ocean and, hopefully, to unlock important data about climate change. For further access to Professor Jim Bishop and his team of researchers, go to the blog!