Methane bubbles stream out of seafloor sediments and carbonates offshore Virginia in this photo from the National Oceanic and Atmospheric Administration ship Okeanos Explorer 2013 ROV Shakedown and Field Trials in the U.S. Atlantic Canyons. Quill worms, anemones, and microbial mats live along the periphery of the seep area. Participants at a town hall at last year's Fall Meeting discussed their needs and preferences for a global database of seafloor cold seeps like this one. Credit: NOAA Office of Ocean Exploration and Research , CC BY 2.0.

Methane emission sites, found everywhere on the world’s seafloors, are interesting to a wide variety of geoscientists and are a source of greenhouse gas. Currently, no global open-source database of these sites exists, but the U.S. Naval Research Laboratory has begun compiling a database of global seafloor anomalies associated with methane emission sites. At a town hall meeting held during AGU’s Fall Meeting 2018, collaborators came together to offer guidance on forming this open-source database of seafloor fluid expulsion anomalies (SEAFLEAs).

Despite increasing numbers of SEAFLEA discoveries, many SEAFLEA locations remain unpublished, and data mining from literature can be tedious and time-consuming. Much about SEAFLEA formation and morphology is still to be discovered—specifically, their distribution on the seafloor. A comprehensive open-source global database of SEAFLEA locations could address these issues.

December’s town hall addressed several questions on how best to establish a collaborative data set:

  • What data are of particular interest: site locations, plume height, hardgrounds, pockmarks, mounds, or other features and phenomena?
  • What form should data be stored in: spreadsheets or shape files?
  • What, if any, data standards should be implemented?

Hunting for SEAFLEAs

SEAFLEAs have been reported for decades in numerous locations, some extensively, using both remote sensing and observational data. These fluid expulsion sites can take on a variety of forms: authigenic carbonate deposits (formed in situ), mounds, bubble plumes, and seafloor methane hydrates, among others. These sites are typically colder than 50°C, earning the name “cold seeps.” They are rich in methane and are likely the result of tectonic stresses or sediment dewatering. Cold seeps are distinctly different from hot (hydrothermal) vents associated with seafloor spreading, which exhibit temperatures over 100°C.

Recently, multibeam sonar systems, which usually identify solid objects, have been modified to show returns (sound reflections) from the water column, where bubble plumes associated with some expulsion sites create strong signals. Increasing use of multibeam sonar promises to be a significant source of SEAFLEA locations. Sonar can pick up not only water column anomalies but also high-backscatter hardgrounds (rocklike formations like authigenic carbonates) commonly associated with cold seeps.

Setting Up the Database

By establishing a collaborative database, we intend to create a central information source and to distribute the administrative burdens. Contributors will add to the database simultaneously with their own research efforts. We intend for the database to be impactful and enduring, creating a foundation for global, regional, and site-specific research into seafloor seepage and serving as a starting point for prediction of regional and global trends, hazards, and other seafloor phenomena.

Most attendees at the town hall were interested in a general data set with no specific features required. They considered phenomena such as areally extensive hardgrounds, mounds, and pockmarks and point source data, such as seep locations, to be equally important. Thus, attendees preferred a data set consisting of geographic information system (GIS)-compatible shape files, which can store both point and shape data with associated features in attribute tables.

Using a GIS program, preferably open source, would also allow multiple users to access and maintain the data set. Remaining hurdles to setting up the database include data verification, a means of collaborating between institutions, details on storage and dissemination, and implementing data standards (e.g., via the Open Geospatial Consortium or the International Hydrographic Organization).

The town hall brought together academic, government, and private sector researchers and scientists at all career levels, each contributing to the initialization of this new database. Although hurdles remain, establishing the community of users, developers, and contributors represents the first step toward an open, collaborative database of seafloor fluid expulsion anomalies.

—Benjamin Phrampus (, American Society for Engineering Education Postdoctoral Research Program, U.S. Naval Research Laboratory, Stennis Space Center, Miss.; and Taylor Lee and Warren Wood, U.S. Naval Research Laboratory, Stennis Space Center, Miss.


Phrampus, B., T. Lee, and W. Wood (2019), Compiling a census for SEAFLEAs, Eos, 100, Published on 02 April 2019.

Text © 2019. The authors. CC BY-NC-ND 3.0
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