Several of the 812 new US Topo quadrangles for Louisiana now display public trails along with improved data layers. Other significant additions include public land survey system information (PLSS), redesign of map symbols, enhanced railroad information and new road source data.
“I am very excited about the 2015 US Topo maps for Louisiana!” said R. Hampton Peele, GIS Coordinator for the Louisiana Geological Survey. “These maps will provide a great reference for our Cartographic Section as we compile our annual geologic map deliverables for the USGS.”
For Louisiana recreationalists and visitors who want to explore the diverse Gulf coast landscape on a bicycle, hiking, horseback or other means, the new trail features on the US Topo maps will come in handy. During the past two years the IMBA, in a partnership with the MTB Project, has been building a detailed national database of trails. This activity allows local IMBA chapters, IMBA members, and the public to provide trail data and descriptions through their website. The MTB Project and IMBA then verify the quality of the trail data provided, ensure accuracy and confirm the trail is legal. This unique crowdsourcing venture has increased the availability of trail data available through The National Map mobile and web apps, and the revised US Topo maps.
Additionally, a widely anticipated addition to the new Louisiana US Topo maps is the inclusion of Public Land Survey System data. PLSS is a way of subdividing and describing land in the US. All lands in the public domain (lands owned by the federal government) are subject to subdivision by this rectangular system of surveys, which is regulated by the U.S. Department of the Interior.
“The US Topo maps provide an excellent instructional tool in our GIS Certification Program,” said Brent Yantis, Director of the University of Louisiana Lafayette Regional Application Center. “They orient students to their environment and provide a fundamental foundation in the development of geospatial concepts. We look forward to this new release.”
These new maps replace the first edition US Topo maps for the Pelican State and are available for free download from The National Map, the USGS Map Locator & Downloader website , or several other USGS applications.
To compare change over time, scans of legacy USGS topo maps, some dating back to the late 1800s, can be downloaded from the USGS Historical Topographic Map Collection.
For more information on US Topo maps: http://nationalmap.gov/ustopo/Updated 2015 version of Saint Landry quadrangle with orthoimage turned on. (1:24,000 scale) (high resolution image 1.3 MB) Updated 2015 version of the Saint Landry quadrangle with the orthoimage turned off to better see the contour intervals. (1:24,000 scale) (high resolution image 1.1 MB) Scan of the 1935 USGS quadrangle of the Turkey Creek area (which covers the Saint Landry map) from the USGS Historic Topographic Map Collection. (1:62, 500 scale) (high resolution image 1.6 MB)
The U.S. Geological Survey National Geospatial Program is developing the 3D Elevation Program (3DEP) to respond to growing needs for high-quality topographic data and for a wide range of other three-dimensional (3D) representations of the Nation's natural and constructed features.
To expand awareness of 3DEP status and plans, as well as provide an open forum for 3DEP stakeholders to communicate and coordinate potential Broad Agency Announcement (BAA) proposals, the USGS is offering numerous state and regional coordination workshops. The meetings will be held throughout the US between early May and June 30th. Locations, dates, times and registration information can be found at: http://1.usa.gov/1IMab1H. The workshops will include in-person and/or virtual participation options.
The primary goal of 3DEP is to systematically collect 3D elevation data in the form of light detection and ranging (lidar) data over the conterminous United States, Hawaii, and the U.S. territories, with data acquired over an 8-year period. Interferometric synthetic aperture radar (ifsar) data will be acquired for Alaska, where cloud cover and remote locations preclude the use of lidar in much of the State. The 3DEP initiative is based on the results of the National Enhanced Elevation Assessment that documented more than 600 business uses across 34 Federal agencies, all 50 States, selected local government and Tribal offices, and private and nonprofit organizations. A fully funded and implemented 3DEP would provide more than $690 million annually in new benefits to government entities, the private sector, and citizens.
3DEP is a "Call for Action" because no one entity can accomplish it independently. 3DEP presents a unique opportunity for collaboration between all levels of government, to leverage the services and expertise of private sector mapping firms that acquire the data, and to create jobs now and in the future. When partners work together, they can achieve efficiencies and lower costs so that 3DEP can become a reality. When 3D elevation data are available to everyone, new innovations will occur in forest resource management, alternative energy, agriculture, and other industries for years to come.
The annual Broad Agency Announcement (BAA) is a competitive solicitation issued to facilitate the collection of lidar and derived elevation data for 3DEP. Federal agencies, state and local governments, tribes, academic institutions and the private sector are eligible to submit proposals. The 3DEP public meetings will introduce this opportunity to the broadest stakeholder community possible and provide a forum for interested parties to discuss elevation data collection needs of mutual interest that could be addressed by a coordinated investment.Map depicts the proposed body of work for 3DEP in Fiscal Year 2015. The BAA awards will add more than 95,000 square miles of 3DEP quality lidar data to the national database. (high resolution image 98 MB)
Water contamination by hormone-disrupting pollutants is a concern for water quality around the world. Existing research has determined that elevated concentrations of Bisphenol-A (BPA), a chemical used in consumer products such as plastic food storage and beverage containers, have been deposited directly into rivers and streams by municipal or industrial wastewater. Now, researchers from the University of Missouri and the U.S. Geological Survey have assessed Missouri water quality near industrial sites permitted to release BPA into the air. As a result, scientists now believe that atmospheric releases may create a concern for contamination of local surface water leading to human and wildlife exposure.
“There is growing concern that hormone disruptors such as BPA not only threaten wildlife, but also humans,” said Chris Kassotis, a doctoral candidate in the Division of Biological Sciences in the College of Arts and Science at MU. “Recent studies have documented widespread atmospheric releases of BPA from industrial sources across the United States. The results from our study provide evidence that these atmospheric discharges can dramatically elevate BPA in nearby environments.”
Water sampling sites were selected based on their proximity to the Superfund National Priorities List (NPL) or locations with reported atmospheric discharges of BPA as identified by the Environmental Protection Agency. Current or historical municipal wastewater treatment sites, which have been shown in the past to contribute hormonally active chemicals to surface water from urban or industrial sources, were also tested. Finally, relatively clean sites were chosen to serve as the control group.
The water then was analyzed for concentrations of BPA, Ethinyl estradiol (EE2), an estrogen commonly used in oral contraceptive pills, and several wastewater compounds. Scientists also measured the total estrogen and receptor activities of the water. This approach is used to measure all chemicals present in the water that are able to bind to and activate (or inhibit) the estrogen or androgen receptors in wildlife and humans. Levels of chemicals were highest in samples with known wastewater treatment plant discharges.
“In addition, we were surprised to find that BPA concentrations were up to 10 times higher in the water near known atmospheric release sites,” said Don Tillitt, adjunct professor of biological sciences at MU, and biochemistry and physiology branch chief with the USGS Columbia Environmental Research Center. “This finding suggests that atmospheric BPA releases may contaminate local surface water, leading to greater exposure of humans or wildlife.”
Concentrations of BPA measured in surface water near these sites were well above levels shown to cause adverse health effects in aquatic species, Kassotis said.
The study, “Characterization of Missouri surface waters near point sources of pollution reveals potential novel atmospheric route of exposure for bisphenol A and wastewater hormonal activity pattern,” was published in the journal, Science of the Total Environment, with funding from MU, the USGS Contaminants Biology Program (Environmental Health Mission Area), and STAR Fellowship Assistance Agreement awarded by the U.S. EPA.
WELLSBORO, Pa. — A piece of the restoration puzzle to save populations of endangered freshwater mussels may have been found, according to a recent U.S. Geological Survey led study. Local population losses in a river may not result in irreversible loss of mussel species; other mussels from within the same river could be used as sources to restore declining populations.
Though they serve a critical role in rivers and streams, freshwater mussels are threatened by habitat degradation such as dams, alteration to river channels, pollution and invasive species. Mussels filter the water and provide habitat and food for algae, macroinvertebrates, and even fish, which are necessary components of aquatic food webs.
“Few people realize the important role that mussels play in the ecosystem," said USGS research biologist Heather Galbraith, lead author of the study. "Streams and rivers with healthy mussel populations tend to have relatively good water quality which is good for the fish and insects that also inhabit those systems."
Mussels in general are poorly understood and difficult to study. Because of this lack of knowledge, population genetics has become a useful tool for understanding their ecology and guiding their restoration.
More than 200 of the nearly 300 North American freshwater mussel species are imperiled, with rapidly dwindling populations. Researchers are providing information to resource managers, who are working to reverse this trend. USGS led research suggests that re-introducing mussels within the same river could reverse population declines without affecting the current genetic makeup of the population.
The research shows that patterns in the genetic makeup of a population occurs within individual rivers for freshwater mussels; and that in the study area, mussels from the same river could be used for restoration.
“That genetic structuring is occurring within individual rivers is good news, because it may be a means of protecting rare, threatened and endangered species from impending extinction,” said Galbraith. “Knowing the genetic structure of a freshwater mussel population is necessary for restoring declining populations to prevent factors such as inbreeding, high mutation rates and low survivorship.”
Knowing that mussels in the same river are similar genetically opens up opportunities for augmenting declining populations or re-introducing mussels into locations where they were historically found. The genetics also highlight the importance of not mixing populations among rivers without additional studies to verify the genetic compatibility of mussels within those rivers.
The international team of researchers from Canada and the United States working to understand mussel genetics found similar genetic patterns among common and endangered mussel species. This is important information for mussel biologists because studying endangered species can be difficult, and researchers may be able to study the genetic structure of common mussels and generalize the patterns to endangered mussels.
Although understanding the genetic structure of mussel populations is important for restoration, genetic tools do have limitations. Researchers found that despite drastic reductions in freshwater mussel populations, there was little evidence of this population decline at the genetic level. This may be due to the extremely long lifespan of mussels, some of which can live to be more than 100 years old.
“Genetics, it turns out, is not a good indicator of population decline; by the time we observe a genetic change, it may be too late for the population,” said Galbraith.
By way of comparison, in fruit flies, which have short lifespans, genetic changes show up quickly within a few generations. Mussels, on the other hand, are long lived animals; therefore it may take decades to see changes in their genetic structure within a population.
The study examined six species of freshwater mussels in four Great Lakes Tributaries in southwestern Ontario. The species are distributed across the eastern half of North America and range in status from presumed extinct to secure. The six mussels were the snuffbox, Epioblasma triquetra; kidneyshell, Ptychobranchus fasciolaris; mapleleaf, Quadrula quadrula; wavy-rayed lampmussel, Lampsilis fasciola; Flutedshell Lasmigona costata; and the threeridge mussel Amblema plicata.
The study, “Comparative analysis of riverscape genetic structure in rare, threatened and common freshwater mussels” is available online in the journal Conservation Genetics.
For more information on freshwater mussels please visit Stranger than Fiction: The Secret Lives of Freshwater Mussels.
USGS has released a preliminary methodology to assess the population level impacts of onshore wind energy development on birds and bats. This wind energy impacts assessment methodology is the first of its kind, evaluating national to regional scale impacts of those bats and birds that breed in and migrate through the United States. The methodology focuses primarily on the effects of collisions between wildlife and turbines.
Primary uses of this new methodology, which is complementary to and incorporates detailed studies and demographic models USGS conducts on key species, include:
- Quantitative measuring of the potential impacts to species’ populations through demographic modeling and the use of potential biologic removal methods.
- Ranking species in terms of their direct and indirect relative risk to wind energy development.
- Recommending species for more intensive demographic modeling or study.
- Highlighting species for which the effects of wind energy development on their populations are projected to be small.
This new draft methodology is based on a robust quantitative and probabilistic framework used by the USGS in energy resource assessments. The assessment methodology also incorporates publicly available information on fatality incidents, population estimates, species range maps, turbine location data and biological characteristics.
The methodology includes a qualitative risk ranking component, as well as a generalized population modelling component. The USGS also repurposed a well-established marine mammal conservation method known as Potential Biological Removal. This methodology identifies the maximum number of animals—not including natural deaths—that may be removed from a marine mammal population while allowing it to reach or maintain its optimum sustainable population. The USGS uses the Potential Biological Removal tool to compare the observed fatalities from collisions with wind turbines to the estimated number of fatalities that can occur before a population would decline.
This methodology also builds on previous USGS research on wind energy, for example, the USGS WindFarm map, released early 2014, that shows the location of all land-based wind turbines in the United States.
Applying expertise in biology, ecology, mapping and resource assessment, the USGS has contributed to the Department of the Interior’s Powering Our Future Initiative with this methodology to quantify the impact of wind energy development on birds and bats.
Throughout the course of this project, USGS scientists have engaged in discussions with a variety of partners and stakeholders, such as the U.S. Fish and Wildlife Service, National Oceanic and Atmospheric Administration, the Bureau of Land Management, Department of Energy, and Department of Defense, as well as industry, non-governmental organizations, and universities. The USGS will now solicit technical comments on this methodology from an expert panel external to the USGS and will consider these comments in developing the final methodology.
Additional ongoing USGS research is focused on understanding potential impacts to wildlife species on a national, regional, and localized scale. Examples of these efforts include developing wildlife and mortality survey protocols, estimating causes and magnitude of fatalities, assessing population level effects, describing bird migration and movement patterns, understanding wildlife interactions with turbines, and developing technologies to reduce fatalities from interactions with turbines.
Marisa Lubeck ( Phone: 303-526-6694 );
New research can help water resource managers quantify critical groundwater resources and assess the sustainability of long-term water use in Minnesota.
U.S. Geological Survey scientists recently estimated annual rates of potential recharge, or the natural replenishment of groundwater, over 15 years across Minnesota. According the study, the statewide mean annual potential recharge rate from 1996‒2010 was 4.9 inches per year (in/yr). Recharge rates increased from west to east across the state and April generally had the highest potential recharge.
Improved estimates of recharge are necessary because approximately 75 percent of drinking water and 90 percent of agricultural irrigation water in Minnesota are supplied from groundwater.
“Resource managers in Minnesota can use this study to help inform water use or water conservation guidelines throughout the state,” said USGS scientist and lead author of the report, Erik Smith.
To maintain a stable supply of groundwater, recharge rates must be high enough to compensate for water that is lost to streams, lakes and other surface-water bodies, or removed for uses such as agriculture. The scientists used data about daily precipitation, minimum and maximum daily temperatures, land cover and soil to model Minnesota’s recharge rates.
During the study period, mean annual potential recharge estimates across Minnesota ranged from less than 0.1 to 17.8 in/yr. Other findings include:
- The highest annual mean recharge estimate across the state was in 2010 at 7 inches, and the lowest mean recharge estimate was 1.3 inches in 2003.
- Some of the lowest potential recharge rates were in the Red River of the North Basin in northwestern Minnesota, generally between 1 and 1.5 in/yr.
- The highest potential recharge rates were in northeastern Minnesota and the Anoka Sand Plain in central Minnesota.
- Eighty-eight percent of the mean annual potential recharge rates were between 2 and 8 in/yr.
- April had the greatest monthly mean at 30 percent of the yearly recharge.
The USGS partnered with the Minnesota Pollution Control Agency on the new study.
For more information on groundwater in Minnesota, please visit the USGS Minnesota Water Science Center website.
The latest coal resource assessment of the Powder River Basin showcases the newly revised USGS’ assessment methodology, which, for the first time, includes an estimate of the reserve base for the entire basin.
The coal reserve base includes those resources that are currently economic (reserves), but also may encompass those parts of a resource that have a reasonable potential for becoming economically available within planning horizons. The complete, final assessment results are available in two USGS publications released today: Professional Paper 1809 and Data Series 912.
The Powder River Basin contains one of the largest resources of low-sulfur, low-ash, subbituminous coal in the world and is the single most important coal basin in the United States.
The most important distinction between this Powder River Basin coal assessment and other, prior assessments, was the inclusion of mining and economic analyses to develop an estimate of the portion of the total resource that is potentially recoverable, not just the original (in-place) resources. Prior resource assessments relied on net coal thickness maps for only selected beds, which provided only in-place resource estimates.
The key to performing the economic analyses was gathering and interpreting a sufficient amount of recent geological data from the extensive coal bed methane development over the past 20 years in the Powder River Basin. This wealth of new data was essential to enable modeling and mapping of all of the significant individual coal beds over the entire Powder River Basin for the first time.
The revised USGS assessment methodology resulted in an estimated original resource of about 1.16 trillion short tons in the Powder River Basin, of which 162 billion short tons are considered recoverable resources (coal reserve base) at a stripping ratio of 10:1 or less. An estimated 25 billion short tons of that coal reserve base met the definition of reserves. A 10:1 stripping ratio is approximately estimated by dividing the total thickness of rock mined to the total thickness of coal recovered.
The coal reserve base includes those resources that are currently economic (reserves), but also may encompass those parts of a resource that have a reasonable potential for becoming economically available. This reserve estimate does not mean that the total amount of coal left in the Powder River Basin could be produced by surface mining technologies. The costs of mining and coal sales prices are not static as both tend to increase over time if supported by demand. If future market prices continue to exceed mining costs, portions of the coal reserve base would be elevated to reserve status (and the converse).
The estimate of the current reserves along with the total coal reserve base provide more meaningful resource information for use by energy planners from local to national perspectives rather than just total in-place resource quantities..
Although no underground mining in the Powder River Basin is expected to occur in the foreseeable future, a substantial, deeper coal resource in beds 10–20 feet thick is estimated at 304 billion short tons in the region.
The USGS Energy Resources Program research efforts yield comprehensive, digital assessments of the quantity, quality, location, and accessibility of the Nation’s coal resources.
To learn more about this or other geologic assessments, please visit the USGS Energy Resources Program website. Stay up to date with USGS energy science by subscribing to our newsletter or by following us on Twitter.
Mining companies, land managers, and regulators now have a wealth of tools to aid in reducing potential mining impacts even before the mine gets started. USGS and various research partners released a special edition of papers specifically targeted at providing modern environmental effect research for modern mining techniques.
Minerals play an important role in the global economy, and, as rising standards of living have increased demand for those minerals, the number and size of mines have increased, leading to larger potential impacts from mining.
“Approaches to protecting the environment from mining impacts have undergone a revolution over the past several decades,” said USGS mineral and environmental expert Bob Seal. “The sustainability of that revolution relies on an evolving scientific understanding of how mines and their waste products interact with the environment.”
Many research conclusions are contained in the special issue, and some of the primary findings are listed here:
- USGS evaluated several tools for predicting pre-mining baseline conditions at a mine, even if no baseline was established. This will make it easier to remediate the mine after it closes.
- USGS also took tools used to screen mine waste for contaminants and tested them for predicting potential sources for contaminants before the mine even got started.
Mitigating while Mining
- Because slag is the byproduct of mineral processing, its physical and chemical properties depend a lot on what the original mined mineral material was.
- Slag from copper, zinc, or nickel may be less attractive for reuse, since it has a higher potential to negatively impact the environment than slag that came from iron or steel production.
- Gold mining runs a lower risk of contaminating the environment with cyanide if mines give enough time for it to safely evaporate and be broken down by sunlight.
- Mine drainage is incredibly complicated. It doesn’t come from a single source, but rather complex interactions between water, air, and micro-organisms like bacteria.
- Mine drainage is not just acid mine drainage—it can be basic, neutral, or even high in salts. All of these drainage types have their own impacts.
- Mine drainage concentrations in streams can actually change based on the time of day.
- USGS tested many of the existing techniques for figuring out what toxic contaminants wind up in stream sediments so managers know the right one for the right job.
- USGS also evaluated a new technique for predicting how toxic certain metals will be in aquatic environments.
The research papers are contained in a special issue of the journal Applied Geochemistry. This research was conducted by scientists from USGS and several collaborating organizations, including the Geological Survey of Canada, InTerraLogic, Montana Bureau of Mines and Geology, Montana Tech, SUNY Oneonta, the University of Maryland, the University of Montana, and the University of Waterloo.
USGS minerals research can help to identify problems before they become problems, or at the very least, help address the impacts that do exist. Learn more about USGS minerals research here, or follow us on www.twitter.com/usgsminerals.
A pine siskin stands on the branch of a northern conifer tree. Photo, USFWS National Digital Library. (High resolution image)
Weaving concepts of ecology and climatology, recent interdisciplinary research by USGS and several university partners reveals how large-scale climate variability appears to connect boom-and-bust cycles in the seed production of the boreal (northern conifer) forests of Canada to massive, irregular movements of boreal birds.
These boreal bird “irruptions” — extended migrations of immense numbers of birds to areas far outside their normal range — have been recorded for decades by birders, but the ultimate causes of the irruptions have never been fully explained.
“This study is a textbook example of interdisciplinary research, establishing an exciting new link between climate and bird migrations” said USGS acting Director Suzette Kimball. “A vital strength of our organization is our ability to pursue scientific issues across the boundaries of traditional academic disciplines.”
The investigation was based on statistical analysis of two million observations of the pine siskin (a finch, Spinus pinus) recorded since 1989 by Project FeederWatch, a citizen science program managed by the Cornell Lab of Ornithology. By methodically counting the birds they see at their feeders from November through early April, FeederWatchers help scientists track continent-wide movements of winter bird populations.
One of several nomadic birds that breed during summer in Canadian boreal forests, pine siskins feed on seed crops of conifers and other tree species. When seed is abundant locally, pine siskins also spend the autumn and winter there. In other years, they may irrupt, migrating unpredictably hundreds or even thousands of kilometers to the south and east in search of seed and favorable habitat. “Superflights” is the term applied to winters (e.g.1997-1998, 2012-2013) when boreal species have blanketed bird feeders across the U.S.
The irruptions of pine siskins and other boreal species follow a lagging pattern of intermittent, but broadly synchronous, accelerated seed production (“masting”) by trees in the boreal forest. Widespread masting in pines, spruces, and firs is driven primarily by favorable climate during the two or three consecutive years required to initiate and mature seed crops. Leading up to masting events, the green developing cones and the promise of abundant seed stimulate higher reproductive rates in birds.
However, seed production is expensive for trees and tends to be much reduced in the years following masting. Consequently, meager seed crops in the years following masting drive boreal birds to search elsewhere for food and overwintering habitat.
The key finding of the new research is that the two principal pine siskin irruption modes – North to South and West to East – correlate closely with spatial patterns of climate variability across North America that are well understood by climatologists. Not surprisingly, severely cold winters tend to drive birds south during the irruption year.
More subtly, the researchers found that favorable and unfavorable climatic conditions of regularly juxtaposed regions called “climate dipoles” two years prior to the irruption also appear to push and pull bird migrations across the continent.
USGS co-author Julio Betancourt commented, “Our study underscores the value of continent-wide biological monitoring. In this case, avid birders across the U.S. and Canada have contributed sustained observations of birds at the same broad geographic scale in which weather and climate have also been observed and understood.”
The research study, authored by Court Strong (University of Utah), Ben Zuckerberg (University of Wisconsin-Madison), Julio Betancourt (USGS-Reston), and Walt Koenig (Cornell University), was published May 11 online in the Proceedings of the National Academy of Sciences.
Storage tanks for produced water from natural gas drilling in the Marcellus Shale gas play of western Pennsylvania. USGS photo, Doug Duncan. (High resolution image)
In a study of 13 hydraulically fractured shale gas wells in north-central Pennsylvania, USGS researchers found that the microbiology and organic chemistry of the produced waters varied widely from well to well.
The variations in these aspects of the wells followed no discernible spatial or geological pattern but may be linked to the time a well was in production. Further, the study highlighted the presence of some organic compounds (e.g. benzene) in produced waters that could present potential risks to human health, if the waters are not properly managed.
Produced water is the term specialists use to describe the water brought to the land surface during oil, gas, and coalbed methane production. This water is a mixture of naturally occurring water and fluid injected into the formation deep underground to enhance production. A USGS Fact Sheet on produced water provides more background information and terminology definitions.
Although the USGS investigators found that the inorganic (noncarbon-based) chemistry of produced waters from the shale gas wells tested in the Marcellus region was fairly consistent from well to well and meshed with comparable results of previous studies (see USGS Energy Produced Waters Project), the large differences in the organic geochemistry (carbon-based, including petroleum products) and microbiology (e.g. bacteria) of the produced waters were striking findings of the study.
“Some wells appeared to be hotspots for microbial activity,” observed Denise Akob, a USGS microbiologist and lead author of the study, “but this was not predicted by well location, depth, or salinity. The presence of microbes seemed to be associated with concentrations of specific organic compounds — for example, benzene or acetate — and the length of time that the well was in production.”
The connection between the presence of organic compounds and the detection of microbes was not, in itself, surprising. Many organic compounds used as hydraulic fracturing fluid additives are biodegradable and thus could have supported microbial activity at depth during shale gas production.
The notable differences in volatile organic compounds (VOCs) from the produced waters of the tested wells could play a role in the management of produced waters, particularly since VOCs, such as benzene, may be a health concern around the well or holding pond. In wells without VOCs, on the other hand, disposal strategies could concentrate on issues related to the handling of other hazardous compounds.
Microbial activity detected in these samples could turn out to be an advantage by contributing to the degradation of organic compounds present in the produced waters. Potentially, microbes could also serve to help mitigate the effects of organic contaminants during the disposal or accidental release of produced waters. Additional research is needed to fully assess how microbial activity can best be utilized to biodegrade organic compounds found in produced waters.
The research article can be found in the most recent edition of Applied Geochemistry, Special Issue on Shale Gas Geochemistry.
If invasive bighead carp and silver carp spread into Lake Erie, there would be enough food available for these species of Asian carp to survive, according to a new study by the U.S. Geological Survey.
This information is critical in helping resource managers mitigate effects of an Asian carp invasion. If bighead and silver carp were to populate Lake Erie, they have the potential to damage native fish populations and the Great Lakes economy.
USGS scientists used satellite imagery of Lake Erie showing algae on the surface to determine how much food would be available for Asian carp. Green algae and blue-green algae, specifically floating algal blooms that can be seen on the surface, are a preferred food source for Asian carp. The water temperatures and algal concentrations detected in Lake Erie from 2002-2011 show that the bighead and silver carps could not only live in this environment, but could continue to grow. The full report is available online.
“Remote sensing imagery shows that Lake Erie has huge areas of available food that are often several times more concentrated than necessary for Asian carp growth, particularly in the western basin,” said USGS scientist Karl Anderson.
Food availability and water temperature are the greatest sources of uncertainty for predicting fish growth potential. Water temperature is a big factor in determining how much bighead and silver carps need to eat. Models developed by USGS scientists helped determine how much algae bighead and silver carps need to eat to survive.
For the past 10 years, algal blooms in Lake Erie have been increasing. Remote sensing images showed that the amount of algae doubled, and in some places quadrupled, from 2002-2011. Throughout the lake, algal blooms encompass several hundred to several thousands square kilometers. Specifically, the western part of Lake Erie has algal concentrations that are several times greater than what is needed for bighead or silver carp to survive.
Seasonal Habitat Quality and Landscape Characteristics Explain Genetic Differences Between Greater Sage-grouse Populations in Wyoming
FORT COLLINS, Colo. — Low-quality nesting and winter seasonal habitats are strong predictors of reduced gene flow between greater sage-grouse breeding locations, according to research just published in Ecology and Evolution and authored by the U.S. Geological Survey and their colleagues at the University of Waterloo.
The study compared the genetic differences between greater sage-grouse breeding areas with seasonal habitat distributions or combinations of landscape factors – such as amount of sagebrush habitat, agriculture fields or roads – to understand how each factor or combination of factors influence effective dispersal of sage-grouse across the state.
Understanding how habitat and landscape features impact the effective dispersal of a species is important for informing management and conservation decisions across large landscapes. Dispersal effectiveness can be measured by gene flow, the rate at which genetic material moves between populations. When populations become small and isolated, a reduction in gene flow can lead to reduced genetic diversity, making those populations potentially less resilient to environmental stressors.
“This research identified which seasonal habitats and individual landscape features facilitate and impede gene flow across the state of Wyoming – which is a stronghold for sage-grouse populations,” said Brad Fedy, one of the authors of the paper and a scientist at the University of Waterloo in Ontario.
Greater sage-grouse are dependent upon sagebrush, so two populations separated only by sagebrush habitat would be expected to have more individuals moving between them and be more genetically similar than two populations separated by a barrier to sage-grouse movement, such as a mountain range or forest.
Researchers found that the juxtaposition and quality of nesting and winter seasonal habitats were the greatest predictors of gene flow for greater sage-grouse in Wyoming. Furthermore, the combinations of high levels of forest cover and highly rugged (steep and uneven) terrain or low levels of sagebrush cover and highly rugged terrain were correlated with low levels of gene flow among sage-grouse populations.
“Maintaining natural levels of gene flow among populations helps ensure resilience for the species,” said Sara Oyler-McCance, a USGS research geneticist and a co-author on the study. “Ultimately, land managers can use this information to identify habitats that are most important for maintaining effective dispersal between populations and to improve future sage-grouse conservation efforts.”
Greater sage-grouse occur in parts of 11 U.S. states and 2 Canadian provinces in western North America. These birds rely on sagebrush ecosystems, which constitute the largest single North American shrub ecosystem and provide vital ecological, hydrological, biological, agricultural, and recreational ecosystem services. The U.S. Fish and Wildlife Service is formally reviewing the status of greater sage-grouse to determine if the species is warranted for listing under the Endangered Species Act.
RESTON, Va.-- The latest tool designed to help manage the threatened piping plover is only a download away; iPlover is the first smartphone data collection application developed by the U.S. Geological Survey and will help those managing plover populations.
iPlover supports a long-established network of partners working to address ongoing impacts on plover populations, such as habitat gain or loss due to storms.
More importantly, data from the app is used to develop models that address long-term management concerns for habitat availability. It also improves the overall quality of coastal geologic information available to effectively manage this species.
The piping plover is a small shorebird that depends on open coastal beaches to breed and raise its young. Listed as threatened along the Atlantic coast in 1986, the piping plover’s conservation has been mandated by the Endangered Species Act. Although Atlantic Coast piping plover numbers have more than doubled since their listing nearly 30 years ago, they are still at risk. Recent estimates place the population at fewer than 2000 pairs, and climate change has introduced new threats to their coastal habitat.
Coastal beaches are dynamic systems and managing them for beach-dependent species like the piping plover requires collecting data on physical and biological characteristics that will be affected by sea level rise. Given the extensive Atlantic breeding range of the piping plover – spanning from North Carolina to Newfoundland – biologists have a lot of ground to cover.
The iPlover app supports the need for coordinated, synchronized data collection. It is a powerful new tool to help scientists and coastal resource managers consistently measure and assess the birds’ response to changes to their habitat. Rather than compiling data from multiple sources and formats, the app gives trained resource managers an easy-to-use platform where they can collect and instantly share data across a diverse community of field technicians, scientists, and managers. iPlover improves scientists’ data gathering and analysis capabilities by simplifying and facilitating consistent data collection and management that interfaces with models of shoreline change and beach geomorphology.
“The data come in from all of our study sites basically in real-time,” said Rob Thieler, USGS scientist and lead developer of the app. “It's already formatted, so data can be quickly plugged into our research models. This should really shorten the time between collecting the data, doing the science, and turning it into actionable information for management.”
“The USGS worked with diverse project partners to incorporate specific data collection needs and enable important stakeholders and partners to contribute data from hundreds of field observations within the plover’s U.S. Atlantic coastal breeding range,” said Andrew Milliken, coordinator of the North Atlantic Landscape Conservation Cooperative. “This included getting inputs from the U.S. Fish and Wildlife Service, National Park Service, state agencies and non-governmental organizations.”
“The app highlights the synergies and benefits of interagency and interdisciplinary science that advances conservation,” Milliken added. “The information collected will not only greatly improve our understanding of impacts from sea level rise, storms and beach management on piping plovers but also how managing for plovers can benefit other beach-dependent species, such as the American oystercatcher.”
Funding for iPlover was provided through the Department of Interior North Atlantic Landscape Conservation Cooperative as part of its Hurricane Sandy response. The app was developed by the USGS’ Woods Hole Coastal and Marine Science Center and the Center for Integrated Data Analytics.
“iPlover is a great example of the USGS’ ability to build and deliver a variety of science applications that use modern technology,” said Nate Booth, USGS Chief of Office of Water Information and former Lead Architect for the USGS Center for Integrated Data Analytics. “It offers research teams great gains in data collection efficiency so that more time can be spent on analyzing the data rather than managing it."
SEATTLE, Wash. — More than 1,000 dams have been removed across the United States because of safety concerns, sediment buildup, inefficiency or having otherwise outlived usefulness. A paper published today in Science finds that rivers are resilient and respond relatively quickly after a dam is removed.
“The apparent success of dam removal as a means of river restoration is reflected in the increasing number of dams coming down, more than 1,000 in the last 40 years,” said lead author of the study Jim O’Connor, geologist with the U.S. Geological Survey. “Rivers quickly erode sediment accumulated in former reservoirs and redistribute it downstream, commonly returning the river to conditions similar to those prior to impoundment.”
Dam removal and the resulting river ecosystem restoration is being studied by scientists from several universities and government agencies, including the USGS and U.S. Forest Service, as part of a national effort to document the effects of removing dams. Studies show that most river channels stabilize within months or years, not decades, particularly when dams are removed rapidly.
“In many cases, fish and other biological aspects of river ecosystems also respond quickly to dam removal,” said co-author of the study Jeff Duda, an ecologist with USGS. “When given the chance, salmon and other migratory fish will move upstream and utilize newly opened habitat.”
The increase in the number of dam removals, both nationally and internationally, has spurred the effort to understand the consequences and help guide future dam removals.
“As existing dams age and outlive usefulness, dam removal is becoming more common, particularly where it can benefit riverine ecosystems,” said Gordon Grant, Forest Service hydrologist. “But it can be a complicated decision with significant economic and ecologic consequences. Better understanding of outcomes enables better decisions about which dams might be good candidates for removal and what the river might look like as a result.”
Sponsored by the USGS John Wesley Powell Center for Analysis and Synthesis, a working group of 22 scientists compiled a database of research and studies involving more than 125 dam removals. Researchers have determined common patterns and controls affecting how rivers and their ecosystems respond to dam removal. Important factors include the size of the dam, the volume and type of sediment accumulated in the reservoir, and overall watershed characteristics and history.
EVERGLADES NATIONAL PARK, Fla.— The largest and longest Burmese Python tracking study of its kind -- here or in its native range -- is providing researchers and resource managers new information that may help target control efforts of this invasive snake, according to a new study led by the U.S. Geological Survey.
Among the findings, scientists have identified the size of a Burmese python’s home range and discovered they share some “common areas” that multiple snakes use.
“These high-use areas may be optimal locations for control efforts and further studies on the snakes’ potential impacts on native wildlife,” said Kristen Hart, a USGS research ecologist and lead author of the study. “Understanding habitat-use patterns of invasive species can aid resource managers in designing appropriately timed and scaled management strategies to help control their spread.”
Using radio and GPS tags to track 19 wild-caught pythons, researchers were able to learn how the Burmese python moved within its home range. The 5,119 days of tracking data led researchers to conclude that python home ranges are an average of 22 square kilometers, or roughly an area 3 miles wide-by-3 miles long, all currently within the park.
The study found pythons were concentrated in slough and coastal habitats, with tree islands being the principal feature of common-use areas, even in areas where they were not the predominant habitat type. The longest movements of individual pythons occurred most often during dry conditions, but took place during “wet” and “dry” seasons.
Burmese pythons are long-lived, large-bodied constricting snakes native to Southeast Asia. Highly adaptable, these ambush predators can reach lengths greater than 19 feet and produce large clutches of eggs that can range from eight to 107 eggs. Burmese pythons were first observed in South Florida’s Everglades National Park in 1979. Since then, they have spread throughout the park. Although recent research indicates the snakes may be having a significant effect on some populations of mid-sized mammals, it has also shown there is little risk to people who visit Everglades National Park.
Invasive species compete with native wildlife for food, and they threaten native biodiversity across the globe. With nearly 50 percent of the imperiled species in the US being threatened by exotic species, a major concern for land managers is the growing number of exotics that are successfully invading and establishing viable populations.
Florida is home to more exotic animals than any other state. Snakes in particular have been shown to pose a high risk of becoming invasive species. The establishment of Burmese pythons in South Florida poses a significant threat to both the sensitive Everglades ecosystem and native species of conservation concern. For example, in the park, wood storks, Florida panthers and Cape Sable seaside sparrows are all species of conservation concern that have home ranges near the common-use areas of the radio-tracked pythons.
The study, “Home Range, Habitat Use, and Movement Patterns of Non-Native Burmese Pythons in Everglades National Park, Florida, USA,” with authors from the USGS, University of Florida, National Park Service, and Davidson College, was published in the journal Animal Biotelemetry.
Diane Noserale ( Phone: 703-648-4333 );
A map showing the many different pieces of Earth’s crust that comprise the nation’s geologic basement is now available from the U.S. Geological Survey. This is the first map to portray these pieces, from the most ancient to recent, by the events that influenced their composition, starting with their origin. This product provides a picture of the basement for the U.S., including Alaska, that can help scientists produce regional and national mineral resource assessments, starting with the original metal endowments in source rocks.
“Traditionally, scientists have assessed mineral resources using clues at or near the Earth’s surface to determine what lies below,” said USGS scientist Karen Lund, who led the project. “This map is based on the concept that the age and origins of basement rocks influenced the nature and location of mineral deposits. It offers a framework to examine mineral resources and other geologic aspects of the continent from its building blocks up,” said Lund.
More than 80 pieces of crust have been added to the nation’s basement since the Earth began preserving crust about 3.6 billion years ago. These basement domains had different ages and origins before they became basement rocks, and this map includes these as key factors that determined their compositions and the original metals that may be available for remobilization and concentration into ore deposits. The map further classifies the basement domains according to how and when they became basement, as these events also influence the specific metals and deposit types that might be found in a region.
Users can identify domains potentially containing specific metals or deposit types. They can configure the companion database to show the construction of the U.S. through time. The map also provides a template to correlate regional to national fault and earthquake patterns. The map is also available on a separate site, where users can combine data and overlay known mineral sites or other features on the domains.
Basement rocks are crystalline rocks lying above the mantle and beneath all other rocks and sediments. They are sometimes exposed at the surface, but often they are buried under miles of rock and sediment and can only be mapped over large areas using remote geophysical surveys. This map was compiled using a variety of methods, including data from national-scale gravity and aeromagnetic surveys.
Crustal rocks are modified several times before they become basement, and these transitions alter their composition. Basement rocks are continental crust that has been modified by a wide variety of plate tectonic events involving deformation, metamorphism, deposition, partial melting and magmatism. Ultimately, continental crust forms from pre-existing oceanic crust and overlying sediments that have been thus modified.
It is not only the myriad processes that result in varying basement rock content but also the time when these processes occurred during the Earth’s history. For example, because the Earth has evolved as a planet during its 4.5 billion year history, early deposit types formed when there was less oxygen in the atmosphere and the thin crust was hotter. The ancient domains are now more stable and less likely to be altered by modern processes that could cause metals to migrate. By contrast, basement rocks that formed out of crust that is less than one billion years old have origins that can be interpreted according to the present-day rates and scales of plate tectonic processes that reflect a more mature planet with a thicker crust.
By incorporating ancient to modern processes, this map offers a more complete and consistent portrait of the nation’s geologic basement than previous maps and presents a nationwide concept of basement for future broad-scale mineral resource assessments and other geologic studies.Map showing basement domains according to generalized original crust types. (High resolution image)
Significant strides in science have been made to better understand potential ground shaking from induced earthquakes, which are earthquakes triggered by man-made practices.
Earthquake activity has sharply increased since 2009 in the central and eastern United States. The increase has been linked to industrial operations that dispose of wastewater by injecting it into deep wells.
The U. S. Geological Survey (USGS) released a report today that outlines a preliminary set of models to forecast how hazardous ground shaking could be in the areas where sharp increases in seismicity have been recorded. The models ultimately aim to calculate how often earthquakes are expected to occur in the next year and how hard the ground will likely shake as a result. This report looked at the central and eastern United States; future research will incorporate data from the western states as well.
This report also identifies issues that must be resolved to develop a final hazard model, which is scheduled for release at the end of the year after the preliminary models are further examined. These preliminary models should be considered experimental in nature and should not be used for decision-making.
USGS scientists identified 17 areas within eight states with increased rates of induced seismicity. Since 2000, several of these areas have experienced high levels of seismicity, with substantial increases since 2009 that continue today. This is the first comprehensive assessment of the hazard levels associated with induced earthquakes in these areas. A detailed list of these areas is provided in the accompanying map, including the states of Alabama, Arkansas, Colorado, Kansas, New Mexico, Ohio, Oklahoma, and Texas.
Scientists developed the models by analyzing earthquakes in these zones and considering their rates, locations, maximum magnitude, and ground motions.
“This new report describes for the first time how injection-induced earthquakes can be incorporated into U.S. seismic hazard maps,” said Mark Petersen, Chief of the USGS National Seismic Hazard Modeling Project. “These earthquakes are occurring at a higher rate than ever before and pose a much greater risk to people living nearby. The USGS is developing methods that overcome the challenges in assessing seismic hazards in these regions in order to support decisions that help keep communities safe from ground shaking.”
In 2014, the USGS released updated National Seismic Hazard Maps, which describe hazard levels for natural earthquakes. Those maps are used in building codes, insurance rates, emergency preparedness plans, and other applications. The maps forecast the likelihood of earthquake shaking within a 50-year period, which is the average lifetime of a building. However, these new induced seismicity products display intensity of potential ground shaking from induced earthquakes in a one-year period. This shorter timeframe is appropriate because the induced activity can vary rapidly with time and is subject to commercial and policy decisions that could change at any point.
These new methods and products result in part from a workshop hosted by the USGS and the Oklahoma Geological Survey. The workshop, described in the new report, brought together a broad group of experts from government, industry and academic communities to discuss the hazards from induced earthquakes.
Wastewater that is salty or polluted by chemicals needs to be disposed of in a manner that prevents contaminating freshwater sources. Large volumes of wastewater can result from a variety of processes, such as a byproduct from energy production. Wastewater injection increases the underground pore pressure, which may lubricate nearby faults thereby making earthquakes more likely to occur. Although the disposal process has the potential to trigger earthquakes, most wastewater disposal wells do not produce felt earthquakes.
Many questions have been raised about whether hydraulic fracturing—commonly referred to as “fracking”—is responsible for the recent increase of earthquakes. USGS’s studies suggest that the actual hydraulic fracturing process is only occasionally the direct cause of felt earthquakes.
Read the newly published USGS report, “Incorporating Induced Seismicity in the 2014 United States National Seismic Hazard Model—Results of 2014 Workshop and Sensitivity Studies.”Cumulative number of earthquakes with a magnitude of 3.0 or larger in the central and eastern United States, 1973-2014. The rate of earthquakes began to increase starting around 2009 and accelerated in 2013-2014. (high resolution image) Research has identified 17 areas in the central and eastern United States with increased rates of induced seismicity. Since 2000, several of these areas have experienced high levels of seismicity, with substantial increases since 2009 that continue today. (high resolution image)
USGS scientists have updated the hydrogeologic framework for the Floridan aquifer system that underlies Florida and parts of Georgia, Alabama, and South Carolina.
The Floridan aquifer system is the principal source of freshwater for agricultural irrigation, industrial, mining, commercial, and public supply in Florida and southeast Georgia. The extensive underground reservoir currently supplies drinking water to about 10 million people residing across the area as well as 50% of the water that is used for agricultural irrigation in the region.
By describing the hydrologic and geologic setting of an aquifer, a hydrogeologic framework enables appropriate authorities and resource managers to monitor an aquifer more accurately, improving their ability to protect these critical resources and determine the near- and long-term availability of groundwater.
As the first update of the framework for the aquifer in over 30 years, the revision incorporates new borehole data into a detailed conceptual model that describes the major and minor units and zones of the system. Its increased accuracy is made possible by data collected in the intervening years by the USGS; the Geological Surveys of Alabama, Florida, Georgia, and South Carolina; the South Florida, Southwest Florida, St Johns River, Suwannee River, and Northwest Florida Water Management Districts; and numerous other state and local agencies.
The USGS is releasing two reports as part of its current assessment of groundwater availability of the Floridan aquifer system.
The first report documents the revised framework.
Williams, L.J., and Kuniansky, E.L., 2015, Revised hydrogeologic framework of the Floridan aquifer system in Florida and parts of Georgia, Alabama, and South Carolina: U.S. Geological Survey Professional Paper 1807, 140 p., 23 pls.
The second report provides datasets that describe the surfaces and thicknesses of selected hydrogeologic units of the Floridan aquifer system. The data depict the top and base of the aquifer system, its major and minor hydrogeologic units and zones, geophysical marker horizons, and the altitude of the 10,000-milligram-per-liter total dissolved solids boundary that defines the approximate fresh and saline parts of the aquifer system.
Williams, L.J., and Dixon, J.F., 2015, Digital surfaces and thicknesses of selected hydrogeologic units of the Floridan aquifer system in Florida and parts of Georgia, Alabama, and South Carolina: U.S. Geological Survey Data Series 926, 24 p.
The USGS is undertaking a series of regional groundwater availability studies to improve our understanding of groundwater availability in major aquifers across the Nation. Regional groundwater availability studies are currently underway to document the supply and demand of this important natural resource for the United States. To find out more about other related groundwater science activities, please visit the USGS Groundwater Resources Program website.
Jon Campbell ( Phone: 703-648-4180 );
The fourth volume of the comprehensive history of the U.S. Geological Survey, Minerals, Lands, and Geology for the Common Defence and General Welfare: Volume 4, 1939‒1961, has been issued as an electronic document.
Featuring more than 200 illustrations, the 704-page Volume 4 focuses on the United States and the USGS in war and peace from the beginning of World War II in Europe to the end of the administration of President Dwight D. Eisenhower. During this period, the USGS developed and adapted new instruments and methods that included airborne magnetometers and radiometers, advanced seismometers, stereoscopic plotters for topographic mapping, geophysical logging (detailed records of geologic formations penetrated by a borehole), and geological sampling from deep wells.
The late Mary C. Rabbitt (1915‒2002), a geophysicist who served with the USGS (1949‒1978), wrote the first three volumes in the series: Volume 1, Before 1879 (1979), Volume 2, 1879‒1904 (1980), and Volume 3, 1904‒1939 (1986). Volume 4 was begun by Rabbitt and completed by coauthor Clifford M. Nelson, a geologist with the USGS since 1976.
Like the earlier books in the series, Volume 4 places USGS operations in mapping and the earth sciences within the wider contexts of national and international history. For instance, USGS development of the airborne magnetometer — an instrument that traces the Earth’s magnetic field, enabling an effective method of exploring for subsurface minerals — followed from a wartime device that U.S. forces used to hunt enemy submarines in World War II.
In the foreword to Volume 4, Mark D. Myers, the 14th USGS Director (2006‒2009), wrote that the volume records USGS support of the Nation’s efforts during "a pivotal interval of transformation for the United States and the agency, …a time of great national sacrifice, rapid expansion of industrial capacity, spectacular scientific and technological advancement, and international leadership."
The likelihood of Asian carp eggs being kept in suspension and hatching in the St. Joseph River in Michigan has been further evaluated using a model that examines a range of multiple flow and water temperature scenarios. Results illustrate the highest percentage of Asian carp eggs at risk of hatching occurs when the streamflow is low and when the water temperature is high. This new study by the University of Illinois and the U.S. Geological Survey is published in the Journal of Great Lakes Research.
“In this study, the Fluvial Egg Drift Simulator (FluEgg) model allowed us to examine the complex dependencies between flow, temperature and egg development,” said USGS hydrologist Ryan Jackson. “This information provides resource managers with a range of conditions under which the St. Joseph River is vulnerable to Asian carp reproduction."
The FluEgg model was used to evaluate egg movement and the likelihood of successful Asian carp reproduction under different streamflow and temperature conditions representative of historical spawning seasons in the St. Joseph River, a tributary to Lake Michigan. Results show that eggs develop faster at warmer water temperatures, therefore requiring less time to drift in the river until hatching. Low streamflows can also be conducive to reproduction when the streamflow is just fast enough to keep most of the eggs in suspension while allowing for the greatest amount of drift time before reaching the lake, thus increasing the likelihood of hatching.
The FluEgg model, developed by University of Illinois researchers in collaboration with the USGS, was first introduced in 2013. The latest version of the model is available online, and includes a user-friendly interface and improved predictions of egg transport in rivers.
Invasive Asian carp consume plankton from the base of the food web and reproduce prolifically which could pose substantial environmental risks and economic impacts to the Great Lakes if they become established.
"This work focuses on the early life stages of Asian carp," said USGS research fish biologist Duane Chapman. "Targeting early life stages can include disrupting spawning activities or egg development in rivers where Asian carp spawn."
Several factors affect the viability of the eggs. The temperature of the water affects how long the eggs need to hatch, and the velocity of the river affects the movement of the eggs and whether the eggs remain in suspension or sink to the bottom. Eggs that settle on the riverbed will likely die, and eggs that are transported down the river and into a lake may not have enough time to develop to the hatching stage before settling to the lakebed.
The reproduction assessment of Asian carp eggs in the St. Joseph River demonstrated the complexity of the problem where the length of the river, velocity and water temperatures cannot be assessed individually. Rather, a holistic analysis is required, where egg development, water-quality characteristics and the hydrodynamics of the river are interconnected and analyzed together.
“Successful reproduction requires a fine balance between the rate of egg development and the variable flow conditions present in a river required to maintain the eggs in suspension,” said Tatiana Garcia, USGS research hydrologist and lead author of the paper.
The paper, “Application of the FluEgg model to predict transport of Asian carp eggs in the St. Joseph River (Great Lakes tributary)” by Tatiana Garcia, Elizabeth A. Murphy, Patrick R. Jackson and Marcelo H. Garcia, is available online.