2015 DOE JGI’s science portfolio delves deeper into the Earth’s data mine

The U.S. Department of Energy Joint Genome Institute (DOE JGI), a DOE Office of Science user facility, has announced that 32 new projects have been selected for the 2015 Community Science Program (CSP). From sampling Antarctic lakes to Caribbean waters, and from plant root micro-ecosystems, to the subsurface underneath the water table in forested watersheds, the CSP 2015 projects portfolio highlights diverse environments where DOE mission-relevant science can be extracted.

“These projects catalyze JGI’s strategic shift in emphasis from solving an organism’s genome sequence to enabling an understanding of what this information enables organisms to do,” said Jim Bristow, DOE JGI Science Deputy who oversees the CSP. “To accomplish this, the projects selected combine DNA sequencing with large-scale experimental and computational capabilities, and in some cases include JGI’s new capability to write DNA in addition to reading it. These projects will expand research communities, and help to meet the DOE JGI imperative to translate sequence to function and ultimately into solutions for major energy and environmental problems.”

The CSP 2015 projects were selected by an external review panel from 76 full proposals received that resulted from 85 letters of intent submitted. The total allocation for the CSP 2015 portfolio is expected to exceed 60 trillion bases (terabases or Tb)-or the equivalent of 20,000 human genomes of plant, fungal and microbial genome sequences. The full list of projects may be found at http://jgi.doe.gov/our-projects/csp-plans/fy-2015-csp-plans/. The DOE JGI Community Science Program also accepts proposals for smaller-scale microbial, resequencing and DNA synthesis projects and reviews them twice a year. The CSP advances projects that harness DOE JGI’s capability in massive-scale DNA sequencing, analysis and synthesis in support of the DOE missions in alternative energy, global carbon cycling, and biogeochemistry.

Among the CSP 2015 projects selected is one from Regina Lamendella of Juniata College, who will investigate how microbial communities in Marcellus shale, the country’s largest shale gas field, respond to hydraulic fracturing and natural gas extraction. For example, as fracking uses chemicals, researchers are interested in how the microbial communities can break down environmental contaminants, and how they respond to the release of methane during oil extraction operations.

Some 1,500 miles south from those gas extraction sites, Monica Medina-Munoz of Penn State University will study the effect of thermal stress on the Caribbean coral Orbicella faveolata and the metabolic contribution of its coral host Symbiodinium. The calcium carbonate in coral reefs acts as carbon sinks, but reef health depends on microbial communities. If the photosynthetic symbionts are removed from the coral host, for example, the corals can die and calcification rates decrease. Understanding how to maintain stability in the coral-microbiome community can provide information on the coral’s contribution to the global ocean carbon cycle.

Longtime DOE JGI collaborator Jill Banfield of the University of California (UC), Berkeley is profiling the diversity of microbial communities found in the subsurface from the Rifle aquifer adjacent to the Colorado River. The subsurface is a massive, yet poorly understood, repository of organic carbon as well as greenhouse gases. Another research question, based on having the microbial populations close to both the water table and the river, is how they impact carbon, nitrogen and sulfur cycles. Her project is part of the first coordinated attempt to quantify the metabolic potential of an entire subsurface ecosystem under the aegis of the Lawrence Berkeley National Laboratory’s Subsurface Biogeochemistry Scientific Focus Area.

Banfield also successfully competed for a second CSP project to characterize the tree-root microbial interactions that occur below the soil mantle in the unsaturated zone or vadose zone, which extends into unweathered bedrock. The project’s goal is to understand how microbial communities this deep underground influence tree-based carbon fixation in forested watersheds by the Eel River in northwestern California.

Several fungal projects were selected for the 2015 CSP portfolio, including one led by Kabir Peay of Stanford University. He and his colleagues will study how fungal communities in animal feces decompose organic matter. His project has a stated end goal of developing a model system that emulates the ecosystem at Point Reyes National Seashore, where Tule elk are the largest native herbivores.

Another selected fungal project comes from Timothy James of University of Michigan, who will explore the so-called “dark matter fungi” – those not represented in culture collections. By sequencing several dozen species of unculturable zoosporic fungi from freshwater, soils and animal feces, he and his colleagues hope to develop a kingdom-wide fungal phylogenetic framework.

Christian Wurzbacher of Germany’s the Leibniz Institute of Freshwater Ecology and Inland Fisheries, IGB, will characterize fungi from the deep sea to peatlands to freshwater streams to understand the potentially novel adaptations that are necessary to thrive in their aquatic environments. The genomic information would provide information on their metabolic capabilities for breaking down cellulose, lignin and other plant cell wall components, and animal polymers such as keratin and chitin.

Many of the selected projects focus on DOE JGI Flagship Plant Genomes, with most centered on the poplar (Populus trichocarpa.) For example, longtime DOE JGI collaborator Steve DiFazio of West Virginia University is interested in poplar but will study its reproductive development with the help of a close relative, the willow (Salix purpurea). With its shorter generation time, the plant is a good model system and comparator for understanding sex determination, which can help bioenergy crop breeders by, for example, either accelerating or preventing flowering.

Another project comes from Posy Busby of the University of Washington, who will study the interactions between the poplar tree and its fungal, non-pathogenic symbionts or endophytes. As disease-causing pathogens interact with endophytes in leaves, he noted in his proposal, understanding the roles and functions of endophytes could prove useful to meeting future fuel and food requirements.

Along the lines of poplar endophytes, Carolin Frank at UC Merced will investigate the nitrogen-fixing endophytes in poplar, willow, and pine, with the aim of improving growth in grasses and agricultural crops under nutrient-poor conditions.

Rotem Sorek from the Weizmann Institute of Science in Israel takes a different approach starting from the hypothesis that poplar trees have an adaptive immunity system rooted in genome-encoded immune memory. Through deep sequencing of tissues from single poplar trees (some over a century old, others younger) his team hopes to gain insights into the tree genome’s short-term evolution and how its gene expression profiles change over time, as well as to predict how trees might respond under various climate change scenarios.

Tackling a different DOE JGI Flagship Plant Genome, Debbie Laudencia-Chingcuangco of the USDA-ARS will develop a genome-wide collection of several thousand mutants of the model grass Brachypodium distachyon to help domesticate the grasses that are being considered as candidate bioenergy feedstocks. This work is being done in collaboration with researchers at the Great Lakes Bioenergy Research Center, as the team there considers Brachypodium “critical to achieving its mission of developing productive energy crops that can be easily processed into fuels.”

Continuing the theme of candidate bioenergy grasses, Kankshita Swaminathan from the University of Illinois will study gene expression in polyploidy grasses Miscanthus and sugarcane, comparing them against the closely related diploid grass sorghum to understand how these plants recycle nutrients.

Baohong Zhang of East Carolina University also focused on a bioenergy grass, and his project will look at the microRNAs in switchgrass. These regulatory molecules are each just a couple dozen nucleotides in length and can downregulate (decrease the quantity of) a cellular component. With a library of these small transcripts, he and his team hope to identify the gene expression variation associated with desirable biofuel traits in switchgrass such as increased biomass and responses to drought and salinity stressors.

Nitin Baliga of the Institute of Systems Biology will use DOE JGI genome sequences to build a working model of the networks that regulate lipid accumulation in Chlamydomonas reinhardtii, still another DOE JGI Plant Flagship Genome and a model for characterizing biofuel production by algae.

Other accepted projects include:

The study of the genomes of 32 fungi of the Agaricales order, including 16 fungi to be sequenced for the first time, will be carried out by Jose Maria Barrasa of Spain’s University of Alcala. While many of the basidiomycete fungi involved in wood degradation that have been sequenced are from the Polyporales, he noted in his proposal, many of the fungi involved in breaking down leaf litter and buried wood are from the order Agaricales.

Now at the University of Connecticut, Jonathan Klassen conducted postdoctoral studies at GLBRC researcher Cameron Currie’s lab at University of Wisconsin-Madison. His project will study interactions in ant-microbial community fungus gardens in three states to learn more about how the associated bacterial metagenomes contribute to carbon and nitrogen cycling.

Hinsby Cadillo-Quiroz, at Arizona State University, will conduct a study of the microbial communities in the Amazon peatlands to understand their roles in both emitting greenhouse gases and in storing and cycling carbon. The peatlands are hotspots of soil organic carbon accumulation, and in the tropical regions, they are estimated to hold between 11 percent and 14 percent, or nearly 90 gigatons, of the global carbon stored in soils.

Barbara Campbell, Clemson University will study carbon cycling mechanisms of active bacteria and associated viruses in the freshwater to marine transition zone of the Delaware Bay. Understanding the microbes’ metabolism would help researchers understand they capabilities with regard to dealing with contaminants, and their roles in the nitrogen, sulfur and carbon cycles.

Jim Fredrickson of Pacific Northwest National Laboratory will characterize functional profiles of microbial mats in California, Washington and Yellowstone National Park to understand various functions such as how they produce hydrogen and methane, and break down cellulose.

Joyce Loper of USDA-ARS will carry out a comparative analysis of all Pseudomonas bacteria getting from DOE JGI the sequences of just over 100 type strains to infer a evolutionary history of the this genus — a phylogeny — to characterize the genomic diversity, and determine the distribution of genes linked to key observable traits in this non-uniform group of bacteria.

Holly Simon of Oregon Health & Science University is studying microbial populations in the Columbia River estuary, in part to learn how they enhance greenhouse gas CO2 methane and nitrous oxide production.

Michael Thon from Spain’s University of Salamanca will explore sequences of strains of the Colletotrichum species complex, which include fungal pathogens that infect many crops. One of the questions he and his team will ask is how these fungal strains have adapted to break down the range of plant cell wall compositions.

Kathleen Treseder of UC Irvine will study genes involved in sensitivity to higher temperatures in fungi from a warming experiment in an Alaskan boreal forest. The team’s plan is to fold the genomic information gained into a trait-based ecosystem model called DEMENT to predict carbon dioxide emissions under global warming.

Mary Wildermuth of UC Berkeley will study nearly a dozen genomes of powdery mildew fungi, including three that infect designated bioenergy crops. The project will identify the mechanisms by which the fungi successfully infect plants, information that could lead to the development of crops with improved resistance to fungal infection and limiting fungicide use to allow more sustainable agricultural practices.

Several researchers who have previously collaborated with the DOE JGI have new projects:

Ludmila Chistoserdova from the University of Washington had a pioneering collaboration with the DOE JGI to study microbial communities in Lake Washington. In her new project, she and her team will look at the microbes in the Lake Washington sediment to understand their role in metabolizing the potent greenhouse gas methane.

Rick Cavicchioli of Australia’s University of New South Wales will track how microbial communities change throughout a complete annual cycle in three millennia-old Antarctic lakes and a near-shore marine site. By establishing what the microbes do in different seasons, he noted in his proposal, he and his colleagues hope to learn which microbial processes change and about the factors that control the evolution and speciation of marine-derived communities in cold environments.

With samples collected from surface waters down to the deep ocean, Steve Hallam from Canada’s University of British Columbia will explore metabolic pathways and compounds involved in marine carbon cycling processes to understand how carbon is regulated in the oceans.

The project of Hans-Peter Klenk, of DSMZ in Germany, will generate sequences of 1,000 strains of Actinobacteria, which represent the third most populated bacterial phylum and look for genes that encode cellulose-degrading enzymes or enzymes involved in synthesizing novel, natural products.

Han Wosten of the Netherlands’ Utrecht University will carry out a functional genomics approach to wood degradation by looking at Agaricomycetes, in particular the model white rot fungus Schizophyllum commune and the more potent wood-degrading white rots Phanaerochaete chrysosporium and Pleurotus ostreatus that the DOE JGI has previously sequenced.

Wen-Tso Liu of the University of Illinois and his colleagues want to understand the microbial ecology in anaerobic digesters, key components of the wastewater treatment process. They will study microbial communities in anaerobic digesters from the United States, East Asia and Europe to understand the composition and function of the microbes as they are harnessed for this low-cost municipal wastewater strategy efficiently removes waster and produces methane as a sustainable energy source.

Another project that involves wastewater, albeit indirectly, comes from Erica Young of the University of Wisconsin. She has been studying algae grown in wastewater to track how they use nitrogen and phosphorus, and how cellulose and lipids are produced. Her CSP project will characterize the relationship between the algae and the bacteria that help stabilize these algal communities, particularly the diversity of the bacterial community and the pathways and interactions involved in nutrient uptake and carbon sequestration.

Previous CSP projects and other DOE JGI collaborations are highlighted in some of the DOE JGI Annual User Meeting talks that can be seen here: http://usermeeting.jgi.doe.gov/past-speakers/. The 10th Annual Genomics of Energy and Environment Meeting will be held March 24-26, 2015 in Walnut Creek, Calif. A preliminary speakers list is posted here (http://usermeeting.jgi.doe.gov/) and registration will be opened in the first week of November.

Researchers find major West Antarctic glacier melting from geothermal sources

Thwaites Glacier, the large, rapidly changing outlet of the West Antarctic Ice Sheet, is not only being eroded by the ocean, it’s being melted from below by geothermal heat, researchers at the Institute for Geophysics at The University of Texas at Austin (UTIG) report in the current edition of the Proceedings of the National Academy of Sciences.

The findings significantly change the understanding of conditions beneath the West Antarctic Ice Sheet where accurate information has previously been unobtainable.

The Thwaites Glacier has been the focus of considerable attention in recent weeks as other groups of researchers found the glacier is on the way to collapse, but more data and computer modeling are needed to determine when the collapse will begin in earnest and at what rate the sea level will increase as it proceeds. The new observations by UTIG will greatly inform these ice sheet modeling efforts.

Using radar techniques to map how water flows under ice sheets, UTIG researchers were able to estimate ice melting rates and thus identify significant sources of geothermal heat under Thwaites Glacier. They found these sources are distributed over a wider area and are much hotter than previously assumed.

The geothermal heat contributed significantly to melting of the underside of the glacier, and it might be a key factor in allowing the ice sheet to slide, affecting the ice sheet’s stability and its contribution to future sea level rise.

The cause of the variable distribution of heat beneath the glacier is thought to be the movement of magma and associated volcanic activity arising from the rifting of the Earth’s crust beneath the West Antarctic Ice Sheet.

Knowledge of the heat distribution beneath Thwaites Glacier is crucial information that enables ice sheet modelers to more accurately predict the response of the glacier to the presence of a warming ocean.

Until now, scientists had been unable to measure the strength or location of heat flow under the glacier. Current ice sheet models have assumed that heat flow under the glacier is uniform like a pancake griddle with even heat distribution across the bottom of the ice.

The findings of lead author Dusty Schroeder and his colleagues show that the glacier sits on something more like a multi-burner stovetop with burners putting out heat at different levels at different locations.

“It’s the most complex thermal environment you might imagine,” said co-author Don Blankenship, a senior research scientist at UTIG and Schroeder’s Ph.D. adviser. “And then you plop the most critical dynamically unstable ice sheet on planet Earth in the middle of this thing, and then you try to model it. It’s virtually impossible.”

That’s why, he said, getting a handle on the distribution of geothermal heat flow under the ice sheet has been considered essential for understanding it.

Gathering knowledge about Thwaites Glacier is crucial to understanding what might happen to the West Antarctic Ice Sheet. An outlet glacier the size of Florida in the Amundsen Sea Embayment, it is up to 4,000 meters thick and is considered a key question mark in making projections of global sea level rise.

The glacier is retreating in the face of the warming ocean and is thought to be unstable because its interior lies more than two kilometers below sea level while, at the coast, the bottom of the glacier is quite shallow.

Because its interior connects to the vast portion of the West Antarctic Ice Sheet that lies deeply below sea level, the glacier is considered a gateway to the majority of West Antarctica’s potential sea level contribution.

The collapse of the Thwaites Glacier would cause an increase of global sea level of between 1 and 2 meters, with the potential for more than twice that from the entire West Antarctic Ice Sheet.

The UTIG researchers had previously used ice-penetrating airborne radar sounding data to image two vast interacting subglacial water systems under Thwaites Glacier. The results from this earlier work on water systems (also published in the Proceedings of the National Academy of Sciences) formed the foundation for the new work, which used the distribution of water beneath the glacier to determine the levels and locations of heat flow.

In each case, Schroeder, who received his Ph.D. in May, used techniques he had developed to pull information out of data collected by the radar developed at UTIG.

According to his findings, the minimum average geothermal heat flow beneath Thwaites Glacier is about 100 milliwatts per square meter, with hotspots over 200 milliwatts per square meter. For comparison, the average heat flow of the Earth’s continents is less than 65 milliwatts per square meter.

The presence of water and heat present researchers with significant challenges.

“The combination of variable subglacial geothermal heat flow and the interacting subglacial water system could threaten the stability of Thwaites Glacier in ways that we never before imagined,” Schroeder said.

New model of Earth’s interior reveals clues to hotspot volcanoes

This is a map view of seismic shear-wave speed in the earth's upper mantle, highlighting the slow wave-speed channels (warm colors) imaged in this study. Where present, the channels align with the direction of tectonic-plate motion (dashed lines). -  Berkeley Seismological Laboratory, UC Berkeley
This is a map view of seismic shear-wave speed in the earth’s upper mantle, highlighting the slow wave-speed channels (warm colors) imaged in this study. Where present, the channels align with the direction of tectonic-plate motion (dashed lines). – Berkeley Seismological Laboratory, UC Berkeley

Scientists at the University of California, Berkeley, have detected previously unknown channels of slow-moving seismic waves in Earth’s upper mantle, a discovery that helps explain “hotspot volcanoes” that give birth to island chains such as Hawaii and Tahiti.

Unlike volcanoes that emerge from collision zones between tectonic plates, hotspot volcanoes form in the middle of the plates. The prevalent theory for how a mid-plate volcano forms is that a single upwelling of hot, buoyant rock rises vertically as a plume from deep within Earth’s mantle the layer found between the planet’s crust and core and supplies the heat to feed volcanic eruptions.

However, some hotspot volcano chains are not easily explained by this simple model, suggesting that a more complex interaction between plumes and the upper mantle is at play, said the study authors.

The newfound channels of slow-moving seismic waves, described in a paper to be published Thursday, Sept. 5, in Science Express, provide an important piece of the puzzle in the formation of these hotspot volcanoes and other observations of unusually high heat flow from the ocean floor.

The formation of volcanoes at the edges of plates is closely tied to the movement of tectonic plates, which are created as hot magma pushes up through fissures in mid-ocean ridges and solidifies. As the plates move away from the ridges, they cool, harden and get heavier, eventually sinking back down into the mantle at subduction zones.

But scientists have noticed large swaths of the seafloor that are significantly warmer than expected from this tectonic plate-cooling model. It had been suggested that the plumes responsible for hotspot volcanism could also play a role in explaining these observations, but it was not entirely clear how.

“We needed a clearer picture of where the extra heat is coming from and how it behaves in the upper mantle,” said the study’s senior author, Barbara Romanowicz, UC Berkeley professor of earth and planetary sciences and a researcher at the Berkeley Seismological Laboratory. “Our new finding helps bridge the gap between processes deep in the mantle and phenomenon observed on the earth’s surface, such as hotspots.”

The researchers utilized a new technique that takes waveform data from earthquakes around the world, and then analyzed the individual “wiggles” in the seismograms to create a computer model of Earth’s interior. The technology is comparable to a CT scan.

The model revealed channels dubbed “low-velocity fingers” by the researchers where seismic waves traveled unusually slowly. The fingers stretched out in bands measuring about 600 miles wide and 1,200 miles apart, and moved at depths of 120-220 miles below the seafloor.

Seismic waves typically travel at speeds of 2.5 to 3 miles per second at these depths, but the channels exhibited a 4 percent slowdown in average seismic velocity.

“We know that seismic velocity is influenced by temperature, and we estimate that the slowdown we’re seeing could represent a temperature increase of up to 200 degrees Celsius,” said study lead author Scott French, UC Berkeley graduate student in earth and planetary sciences.

The formation of channels, similar to those revealed in the computer model, has been theoretically suggested to affect plumes in Earth’s mantle, but it has never before been imaged on a global scale. The fingers are also observed to align with the motion of the overlying tectonic plate, further evidence of “channeling” of plume material, the researchers said.

“We believe that plumes contribute to the generation of hotspots and high heat flow, accompanied by complex interactions with the shallow upper mantle,” said French. “The exact nature of those interactions will need further study, but we now have a clearer picture that can help us understand the ‘plumbing’ of Earth’s mantle responsible for hotspot volcano islands like Tahiti, Reunion and Samoa.”

Hawaiian hotspot variability attributed to small-scale convection

Three-dimensional image showing predicted mantle temperatures (blue = warm, red = hot, white = hottest) and a plume of hot mantle rising beneath the Hawaiian hotspot. -  Maxim Ballmer, SOEST/ UHM
Three-dimensional image showing predicted mantle temperatures (blue = warm, red = hot, white = hottest) and a plume of hot mantle rising beneath the Hawaiian hotspot. – Maxim Ballmer, SOEST/ UHM

Small scale convection at the base of the Pacific plate has been simulated in a model of mantle plume dynamics, enabling reasearchers to explain the complex set of observations at the Hawaiian hotspot, according to a new study posted online in the June 26th edition of Nature Geoscience. “A range of observations cannot be explained by the classical version of the mantle plume concept,” says Maxim Ballmer, Post Doctoral Researcher in the Department of Geology and Geophysics in the School of Ocean and Earth Science and Technology (SOEST) at UHM. These observations include the occurrence of secondary volcanism away from the hotspot (e.g., Diamond Head, Punchbowl, Hanauma Bay), as well as the chemical asymmetry (Mauna Loa compared to Mauna Kea) and temporal variability (over timescales greater than 10,000,000 years) of hotspot volcanism itself.

Ballmer and colleagues, including advisor Garrett Ito, Associate Professor, in the Department of Geology and Geophysics in the SOEST at UHM, designed a geodynamic model of the mantle that successfully predicts a large range of observations thus providing insight into the composition and dynamics of the mantle. Ballmer says the findings of their model, “make an important contribution toward understanding the origin of volcanism away from plate boundaries. This is a long-standing question in our community that potentially provides general insight into the dynamics of our planet, and particularly into the make-up of the deepest mantle, from where mantle plumes originate. For many reasons, understanding the deepest mantle is relevant for questions about the early days of Earth, and the origin of water and life.”

These findings came as a bit of a surprise. Although small-scale convection was one hypothesis for explaining late-stage rejuvenated volcanism on the islands, Ito reports, “this study is the first to qualitatively explore this mechanism and to show that it can explain both rejuvenated as well as arch volcanism, well away from the islands.”

As a next step in understanding mantle dynamics, Ballmer hopes to explain some of the characteristics of the Hawaiian plume that have been revealed by SOEST – UHM colleague Cecily Wolfe using seismic earthquake tomography. To do this, he will simulate a thermochemical mantle plume, which in some ways behaves similarly to the upwellings in lava lamps. A thermochemical plume is a plume that is hot (i.e. thermally buoyant), but compositionally dense. Such a plume typically behaves more complicatedly than a classical plume.

Scientists delve into ‘hotspot’ volcanoes along Pacific Ocean Seamount Trail

Like a string of underwater pearls, the Louisville Seamount Trail is strung across the Pacific. -  IODP
Like a string of underwater pearls, the Louisville Seamount Trail is strung across the Pacific. – IODP

Nearly half a mile of rock retrieved from beneath the seafloor is yielding new clues about how underwater volcanoes are created and whether the hotspots that led to their formation have moved over time.

Geoscientists have just completed an expedition to a string of underwater volcanoes, or seamounts, in the Pacific Ocean known as the Louisville Seamount Trail.

There they collected samples of sediments, basalt lava flows and other volcanic eruption materials to piece together the history of this ancient trail of volcanoes.

The expedition was part of the Integrated Ocean Drilling Program (IODP).

“Finding out whether hotspots in Earth’s mantle are stationary or not will lead to new knowledge about the basic workings of our planet,” says Rodey Batiza, section head for marine geosciences in the National Science Foundation’s (NSF) Division of Ocean Sciences.

Tens of thousands of seamounts exist in the Pacific Ocean. Expedition scientists probed a handful of the most important of these underwater volcanoes.

“We sampled ancient lava flows, and a fossilized algal reef,” says Anthony Koppers of Oregon State University. “The samples will be used to study the construction and evolution of individual volcanoes.”

Koppers led the expedition aboard the scientific research vessel JOIDES Resolution, along with co-chief scientist Toshitsugu Yamazaki from the Geological Survey of Japan at the National Institute of Advanced Industrial Science and Technology.

IODP is supported by NSF and Japan’s Ministry of Education, Culture, Sports, Science and Technology.

Over the last two months, scientists drilled 1,113 meters (3,651 feet) into the seafloor to recover 806 meters (2,644 feet) of volcanic rock.

The samples were retrieved from six sites at five seamounts ranging in age from 50 to 80 million years old.

“The sample recovery during this expedition was truly exceptional. I believe we broke the record for drilling igneous rock with a rotary core barrel,” says Yamazaki.

Igneous rock is rock formed through the cooling and solidification of magma or lava, while a rotary core barrel is a type of drilling tool used for penetrating hard rocks.

Trails of volcanoes found in the middle of tectonic plates, such as the Hawaii-Emperor and Louisville Seamount Trails, are believed to form from hotspots–plumes of hot material found deep within the Earth that supply a steady stream of heated rock.

As a tectonic plate drifts over a hotspot, new volcanoes are formed and old ones become extinct. Over time, a trail of volcanoes is formed. The Louisville Seamount Trail is some 4,300 kilometers (about 2,600 miles) long.

“Submarine volcanic trails like the Louisville Seamount Trail are unique because they record the direction and speed at which tectonic plates move,” says Koppers.

Scientists use these volcanoes to study the motion of tectonic plates, comparing the ages of the volcanoes against their location over time to calculate the rate at which a plate moved over a hotspot.

These calculations assume the hotspot stays in the same place.

“The challenge,” says Koppers, “is that no one knows if hotspots are truly stationary or if they somehow wander over time. If they wander, then our calculations of plate direction and speed need to be re-evaluated.”

“More importantly,” he says, “the results of this expedition will give us a more accurate picture of the dynamic nature of the interior of the Earth on a planetary scale.”

Recent studies in Hawaii have shown that the Hawaii hotspot may have moved as much as 15 degrees latitude (about 1,600 kilometers or 1,000 miles) over a period of 30 million years.

“We want to know if the Louisville hotspot moved at the same time and in the same direction as the Hawaiian hotspot. Our models suggest that it’s the opposite, but we won’t really know until we analyze the samples from this expedition,” says Yamazaki.

In addition to the volcanic rock, the scientists also recovered sedimentary rocks that preserve shells and an ancient algal reef, typical of living conditions in a very shallow marine environment.

These ancient materials show that the Louisville seamounts were once an archipelago of volcanic islands.

“We were really surprised to find only a thin layer of sediments on the tops of the seamounts, and only very few indications for the eruption of lava flows above sea level,” says Koppers.

The IODP Louisville Seamount Trail Expedition wasn’t solely focused on geology.

More than 60 samples from five seamounts were obtained for microbiology research.

Exploration of microbial communities under the seafloor, known as the “subseafloor biosphere,” is a rapidly developing field of research.

Using the Louisville samples, microbiologists will study both living microbial residents and those that were abundant over a large area, but now occupy only a few small areas.

They will examine population differences in microbes in the volcanic rock and overlying sediments, and in different kinds of lava flows.

They will also look for population patterns at various depths in the seafloor and compare them with seamounts of varying ages.

Samples from the Louisville Seamount Trail expedition will be analyzed to determine their age, composition and magnetic properties.

The information will be pieced together like a puzzle to create a story of the eruption history of the Louisville volcanoes.

It will then be compared to that of the Hawaiian volcanoes to determine whether hotspots are on the move.

The IODP is an international research program dedicated to advancing scientific understanding of the Earth through drilling, coring and monitoring the subseafloor.

Hawaiian hot spot has deep roots

Seismic image of mantle plume
Seismic image of mantle plume

Hawaii may be paradise for vacationers, but for geologists it has long been a puzzle. Plate tectonic theory readily explains the existence of volcanoes at boundaries where plates split apart or collide, but mid-plate volcanoes such as those that built the Hawaiian island chain have been harder to fit into the theory. A classic explanation, proposed nearly 40 years ago, has been that magma is supplied to the volcanoes from upwellings of hot rock, called mantle “plumes,” that originate deep in the Earth’s mantle. Evidence for these deep structures has been sketchy, however. Now, a sophisticated array of seismometers deployed on the sea floor around Hawaii has provided the first high-resolution seismic images of a mantle plume extending to depths of at least 1,500 kilometers (932 miles).

This unprecedented glimpse of the roots of the Hawaiian “hot spot” is the product of an ambitious project known as PLUME, for Plume-Lithosphere Undersea Melt Experiment, which collected and analyzed two years of data from sea floor and land-based seismometers.

“One of the reasons it has taken so long to create these kinds of images is because many of the major hot spots are located in the middle of the oceans, where it has been difficult to put seismic instruments,” says study co-author Sean Solomon, director of the Carnegie Institution’s Department of Terrestrial Magnetism. “The Hawaiian region is also distant from most of the earthquake zones that are the sources of the seismic waves that are used to create the images. Hawaii has been the archetype of a volcanic hotspot, and yet the deep structure of Hawaii has remained poorly resolved. For this study we were able to take advantage of a new generation of long-lived broad band seismic instruments that could be set out on the seafloor for periods of a year at a time.”

The PLUME seismic images show a seismic anomaly beneath the island of Hawaii, the chain’s largest and most volcanically active island. Critics of the plume model have argued that the magma in hot spot volcanoes comes from relatively shallow depths in the upper mantle (less than 660 kilometers), not deep plumes, but the anomaly observed by the PLUME researchers extends to at least 1,500 kilometers. Rock within the anomaly is also calculated to be significantly hotter than its surroundings, as predicted by the plume model.

“This has really been an eye-opener,” says Solomon. “It shows us that the anomalies do extend well into the lower mantle of the Earth.”

Erik Hauri, also of Carnegie’s Department of Terrestrial Magnetism, led the geochemical component of the research. “We had suspected from geochemistry that the center of the plume would be beneath the main island, and that turns out to be about where the hot spot is centered,” he says. “We also predicted that its width would be comparable to the size of island of Hawaii and that also turned out to be true. But those predictions were merely theoretical. Now, for the first time, we can really see the plume conduit.”

Has the question of hot spots and mantle plumes been settled at last? “We believe that we have very strong evidence that Hawaii is underlain by a plume that extends at least to 1,500 kilometers depth,” says Solomon. “It may well extend deeper, we can’t say on the basis of our data, but that is addressable with global datasets, now that our data have been analyzed. So it’s a very strong vote in favor of the plume model.”

The lead author of the study, published in the December 4, 2009 issue of Science, is Cecily Wolfe, a former Carnegie Fellow at the Carnegie Institution’s Department of Terrestrial Magnetism now at the University of Hawaii at Manoa. Other authors are S.C. Solomon and E.H. Hauri, Carnegie Institution for Science; G. Laske and J.A. Orcutt, Scripps Institution of Oceanography; J. A. Collins and R.S. Detrick, Woods Hole Oceanographic Institution; and D. Bercovici, Yale University. The PLUME project is supported by the National Science Foundation.

Bent tectonics: How Hawaii was bumped off

More than 80 undersea volcanoes and a multitude of islands are dotted along the Hawaii-Emperor seamount chain like pearls on a necklace. A sharp bend in the middle is the only blemish. The long-standing explanation for this distinctive feature was a change in direction of the Pacific oceanic plate in its migration over a stationary hotspot – an apparently unmoving volcano deep within the earth.


According to the results of an international research group, of which Ludwig-Maximilians-Universität München geophysicist Professor Hans-Peter Bunge was a member, however, the hotspot responsible for the Hawaii-Emperor seamount chain was not fixed. Rather it had been drifting quite distinctly southward. Nearly 50 million years ago, it finally came to rest while the Pacific plate steadily pushed on, the combination of which resulted in the prominent bend. The movements of hotspots are determined by circulations in the earth’s mantel. “These processes are not of mere academic interest,” Bunge emphasizes. “Mantel circulation models help us understand the forces that act on tectonic plates. This in turn is essential for estimating the magnitude and evolution of stresses on the largest tectonic fault lines, that is the sources of many major earthquakes.”

The characteristic bend in the trail of the 5000 kilometer long Hawaii-Emperor seamount chain is one of the most striking topographical features of the earth, and is an identifying feature in representations of the Pacific Ocean floor. For a long time, textbooks have explained the creation of the Hawaii-Emperor chain as an 80 million year-long migration of the Pacific oceanic plate over a stationary hotspot. Hotspots are volcanoes rooted deep within the bowels of the earth, from which hot material is constantly pushing its way up to the surface. According to this now obsolete scenario, the bend would have come about as the Pacific plate abruptly changed direction.

In the past 30 years, geophysicists had also depended on the apparently unchanging locations of hotspots in the earth’s mantel in their definition of a global reference for plate tectonics. More recent investigations, however, suggest that hotspots are less stationary than so far assumed. An international research group, of which Professor Hans-Peter Bunge of the LMU Munich Department of Earth and Environmental Sciences was a member, took a closer look at certain evidence pointing towards substantial inherent motion of the underground volcanoes, and has now confirmed this evidence.

“Paleomagnetic observations suggest that the bend in the Hawaii-Emperor chain is not the result of a change in the relative motion of the Pacific plate,” Bunge states. “On the contrary, it seems the hotspot had been drifting rapidly in a southward direction between 80 and 40 million years ago before it came to a complete halt.” If the trail of the Hawaiian hotspot is corrected to include this drift, the result implies a largely constant movement of the Pacific plate over the last 80 million years. The bend ultimately came about as the hotspot started to slow down.

The driving force behind the migration of the hotspot is the circulation of material under the surface of our planet. “The earth’s interior is in constant motion,” reports Bunge. “Over geological timescales, this motion compares to the weather patterns in our atmosphere. These patterns can easily lead to a change in position of hotspots. Numerical simulations of this global circulation in the earth’s mantel allow us to retrace these motions in unprecedented detail.”

The new data will now be entered into the mantel circulation models presently used. These calculations help explain the driving and resisting forces acting on tectonic plates. “And we need to understand these forces because they are essential for estimating the magnitude and evolution of stresses on the major tectonic fault lines – that is, the sources of many major earthquakes on our planet,” says Bunge. The findings to come from these models will allow scientists to improve their computer models by checking their calculations against observations.

Simulations and ancient magnetism suggest mantle plumes may bend deep beneath Earth’s crust

Computer simulations, paleomagnetism and plate motion histories described in today’s issue of Science reveal how hotspots, centers of erupting magma that sit atop columns of hot mantle that were once thought to remain firmly fixed in place, in fact move beneath Earth’s crust.

Scientists believe mantle plumes are responsible for some of the Earth’s most dramatic geological features, such as the Hawaiian islands and Yellowstone National Park. Some plumes may have shallow sources, but a few, such as the one beneath Hawaii, appear to be rooted in the deepest mantle, near Earth’s core.

Such deep plumes have long been thought to be so immobile that the motions of continental and oceanic plates were measured against them, but University of Rochester geophysicist John Tarduno and his colleagues at Ludwig-Maximilians, Münster, and Stanford universities have combined magnetic evidence from the Pacific sea floor with computer modeling to show how the plume beneath Hawaii likely bent-its root barely moving while its top moved nearly 1,000 miles across the underside of the Pacific Ocean.

“In 2003, we showed that the hotspot-the plume-that created the Hawaiian chain of islands must have moved. We suggested that mantle motion was involved, but the cause of the change in motion remained a mystery,” says Tarduno.

Tarduno cites five possible mechanisms in Science, but one in particular, he says, stands out as a likely explanation for the way the Hawaiian chain of islands and seamounts formed. “We know from theory and from models, including work by Ulrich Hansen and Norm Sleep, that a plume can move slightly near its base, potentially contributing to motion of the Hawaiian hotspot and hotspots elsewhere,” says Tarduno. “But a key observation came from a numerical simulation resulting from Hans-Peter Bunge’s models, which show how the upper end of the plume, starting at 1500 depth, can drift like a candle flame drawn toward a draft.”

The draft in this case, he says, is an ancient oceanic ridge in the Pacific where the seafloor spreads, allowing magma to bubble up through the ocean crust. The ancient ridge is now lost to subduction, but its past presence is recorded by a few magnetic lineations in oceanic crust south of the Bering Sea. The ridge was active around 80 million years ago but extinguished completely by 47 million years ago. Those dates correspond very closely with the motion history Tarduno detected in the Hawaiian hotspot.

In 2001, Tarduno and an international team spent two months aboard the ocean drilling ship JOIDES Resolution, retrieving samples of rock from the Emperor-Hawaiian seamount chain miles beneath the sea’s surface. The team started at the northern end of the chain, near Japan, braving cold, foggy days and dodging the occasional typhoon to pull up several long cores of rock as they worked their way south. Using a highly sensitive magnetic device called a SQUID (Superconducting Quantum Interference Device), Tarduno’s team discovered that the magnetism of the cores did not fit with the conventional wisdom of fixed hotspots.

The magnetization of the lavas recovered from the northern end of the Emperor-Hawaiian chain suggested these rocks were formed much farther north than the current hotspot, which is forming Hawaii today. As magma forms, magnetite, a magnetically sensitive mineral, records the Earth’s magnetic field just like a compass. As the magma cools and becomes solid rock, the “compass” orientation is locked in place, preserving a precise record of the latitude of origin.

If the Hawaiian hot spot had always been fixed at its current location of 19 degrees north, then all the rocks of the entire chain should have formed and cooled there, preserving the magnetic signature of 19 degrees even as the Pacific plate dragged the new stones north-westward. Tarduno’s team, however, found that the more northern their samples, the higher the samples’ latitude. The northern-most lavas they recovered were formed at over 30 degrees north about 80 million years ago, nearly a thousand miles from where the hot spot currently lies.

“The only way to account for these findings is if the hotspot itself was moving south,” says Tarduno. His magnetic readings leveled off at a latitude of nearly 19 degrees, suggesting that the magma plume ceased moving in the area it resides in today.

In addition to the “draft” created by the upwelling of magma into the paleo-ridge, Tarduno says that theory and computer simulations suggest that the most a plume can bend under such conditions would result in about 1,000 miles of movement across the crust-matching what he sees as the distance between the start and stop points of the Hawaiian hotspot. He points out that the bending of a mantle plume helps reconcile the evidence of mobile hotspots on the Earth’s crust with the theories that suggest plumes originate in the deepest mantle where high viscosity limits rapid motion. He points out that the plume-ridge capture mechanism may also help explain seemingly anomalous volcanic features on the seafloor, and help geoscientists to use ancient volcanic tracks to understand the past flow of Earth mantle.

Magma And Volcanoes: Physicists Explain Dance Marathon Of Wispy Feature In Roiling Fluids





University of Chicago physicists Wendy Zhang (left) and Laura Schmidt explain a feature of convecting fluids that colleagues have observed in laboratory experiments. The feature may help explain how hotspot volcanism created the Hawaiian Islands and other such landforms. (Credit: Dan Dry)
University of Chicago physicists Wendy Zhang (left) and Laura Schmidt explain a feature of convecting fluids that colleagues have observed in laboratory experiments. The feature may help explain how hotspot volcanism created the Hawaiian Islands and other such landforms. (Credit: Dan Dry)

Theoretical physicists at the University of Chicago are suggesting how thin spouts of magma in the Earth’s mantle can persist long enough to form hotspot volcanism of the type that might have created the Hawaiian Islands.



Their calculations also apply to tendrils only a few inches long that form in convecting fluids under laboratory conditions. University of Chicago graduate student Laura Schmidt and Wendy Zhang, an Assistant Professor in Physics, will detail their findings in the Feb. 1 issue of the journal Physical Review Letters.



The work was inspired by laboratory experiments conducted by Anne Davaille in France that mimic, in a simplified way, convecting bubbles of magma as they might look deep beneath the Earth’s surface. “This is one robust feature of thermal convection,” Zhang said.



“It’s a useful thing to know because it’s the kind of thing that happens in all sorts of different industries, in all sorts of different contexts.” These include oil extraction, the chemical industry and in certain biotechnological applications.



Earth scientists also have theorized that mantle plumes form on a regional scale in the Earth’s interior, sometimes breaking the surface to form small landmasses, including Hawaii and Iceland. Nevertheless, debate swirls around how, or even if, mantle plumes can account for such surface features.



Geophysicists often liken a pot of boiling water as a smaller, more rapid version of the convection that takes place in the mantle, the layer of Earth that lies between the surface crust and its core. But unlike a pot of water, the Earth’s interior consists of layers with different properties.



In laboratory experiments, Anne Davaille, a geophysicist at the University of Paris 7, studies convection in a small tank by heating two layers of colored liquids of differing densities. She observed the formation and persistence of thin tendrils between the layers, which correspond to subsurface plumes measuring scores of miles across.


“It seems so thin and tenuous, how could it possibly manage to hold itself in place over time as everything else is going on around it?” Zhang asked. “Somehow, they manage to hold themselves together.”



The tendrils persist for hours, even as experimental conditions change. “These tendrils have fluid flowing through them, and it starts to mix the two layers,” Schmidt said. “When the two layers mix, then the viscosity of the layers changes as well.”



Following a series of visits to Davaille’s lab, Schmidt and Zhang sought to mathematically explain the phenomenon.



“When you look at the shape of these very thin tendrils, there’s something very striking that Anne noticed right away,” Zhang said. The tendrils seem to emerge from flow lines that resemble the flared-out end of a trumpet. This trumpet shape marked the location of a stagnation point. Both Davaille’s experiments and Schmidt’s calculations agree: The thinnest tendrils that persist have a stagnation point.



Schmidt had seen a similar stagnation point in experiments she conducted in the laboratory of Sidney Nagel, the Stein-Freiler Distinguished Service Professor in Physics at the University of Chicago. Those experiments involved unmixable fluids, such as water and oil, instead of the fresh water and salt water mixing in Davaille’s laboratory.



Nevertheless, the experimental similarities provided Schmidt and Zhang insights that helped solve the problem. In previous studies, other theoreticians suggested how large flows might rise through the tendrils from the base of the hot spots, Schmidt said. She and Zhang approached the problem differently.



“We include the effect of the stagnation point,” Schmidt explained. “Our tendrils are really a thin skin or thin layer of the surface between the fluids that is drawn up. It’s not a bulk flow going up through the tendril.”