Oceanography The Official Magazine of
The Oceanography Society
Volume 23 Issue 01

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Volume 23, No. 1
Pages 34 - 36

BOX • Seamount Discovery Tool Aids Navigation to Uncharted Seafloor Features

David T. SandwellPaul Wessel
First Paragraph

Wessel et al. (2010) highlight the need for a systematic mapping of seamounts in ocean basins. They estimate that 100,000 or 90% of the seamounts greater than 1-km tall are unobserved by either ship soundings or satellite gravity. There are two reasons why most of these relatively large, predicted seamounts remain uncharted. First, satellite-derived gravity is only able to reliably measure seamounts that are more than 2-km tall, although smaller seamounts can be detected (Wessel, 2001). Second, the freely available ship sounding data collected during the past 50 years only covers 10% of the seafloor at the 1-minute resolution needed to detect these 1-km and taller seamounts (Becker et al., 2009). Based on current trends in seafloor mapping, the rate of seamount discoveries is not likely to change significantly because modern research surveys are focused on particular areas of high scientific interest such as mid-ocean ridges, continental margins, and subduction zones. This exploration strategy has resulted in gaps in remote areas of up to 600 km by 300 km. As Figure 1 shows, more than 50% of the seafloor lies more than 9.5 km from the nearest ship sounding. This sparse coverage, combined with a relatively random spatial distribution of seamounts, results in the situation today where there are even 3-km and 4-km tall seamounts that have not been surveyed by ships.


Sandwell, D.T., and P. Wessel. 2010. Box 3: Seamount discovery tool aids navigation to uncharted seafloor features. Oceanography 23(1):34–36, https://doi.org/10.5670/oceanog.2010.87.


Becker, J.J., D.T. Sandwell, W.H.F. Smith, J. Braud, B. Binder, J. Depner, D. Fabre, J. Factor, S. Ingalls, S.-H. Kim, and others. 2009. Global bathymetry and elevation data at 30 arc seconds resolution: SRTM30_PLUS. Marine Geodesy 32(4):355–371, https://doi.org/10.1080/01490410903297766.

Hammond, S., J. McDonough, and C. Russell. 2010. Box 5: The NOAA ship Okeanos Explorer: New ways for exploring the ocean. Oceanography 23(1):88–89.

Smith, W.H.F., and D. Sandwell. 1997. Global seafloor topography from satellite altimetry and ship depth soundings. Science 277:1,956–1,962.

Wessel, P. 2001. Global distribution of seamounts inferred from gridded Geosat/ERS-1 altimetry. Journal of Geophysical Research 106(B9):19,431–19,441.

Wessel, P., D.T. Sandwell, and S.-S. Kim. 2010. The global seamount census. Oceanography 23(1):24–33.