Dugong
Lau Basin, Tonga, SW Pacific Ocean
15.45S, 175.78W; reported depth -1,170 m (seamount)
All times local (Fiji Standard = UTC + 12 hours)
New active submarine volcano found in North Lau Basin, E of Fiji
According to the Australian Commonwealth Scientific and Industrial Research
Organization (CSIRO), several large active submarine volcanoes, spreading ridges, and rift zones
have been discovered in the Northwest Lau back-arc basin, NE of Fiji Island (figure 1), by a team
of Australian and American scientists aboard the CSIRO Marine National Facility Research
Vessel Southern Surveyor during a research cruise in Spring 2008 (CSIRO, 2008b). While
mapping previously uncharted areas for submarine volcanic and hot spring activity with
multibeam sonar and various other techniques, the team located several active volcanoes, one of
which they named Dugong. The depth of Dugong is given in the InterRidge Vents Database [Ver.
3.1] (2013), and its location was plotted on figure 1 based on coordinates given in Lupton and
others (2012).
Figure 1. Two maps showing (lower left) North Island, New Zealand (in black) and selected plate
tectonic features along the Kermadec and Tonga trenches (hachured line with teeth on upthrown
side) and (larger map) Dugong (white square) and other features such as the main spreading
centers, geographical features, and subaerial volcanoes (open yellow triangles). Note Niuafo’ou
volcano and island. The base maps in figure 1 came from Keller and others (2008), a study
primarily discussing the area in the rectangle on the larger map. The sea floor was mapped with
multibeam sonar (soundings normal to the ship’s track). Abbreviations are as follows: VFR - Valu
fa ridge; ELSC - East Lau spreading center; ILSC - Intermediate Lau spreading center; CLSC Central Lau spreading center; LETZ - Lau Extensional transform zone; PR - Peggy Ridge;
NWLSC - Northwest Lau spreading center; NSC - Niuafo'ou spreading center (location of
Rochambeau Rifts); NELSC - Northeast Lau spreading center; FSC - Fonualei spreading center;
and MTJ - Mangatolu triple junction. Courtesy of Keller and others (2008).
As shown in figure 2, the greater Dugong structure is dominated by a 5-km-diameter
caldera at a depth of 1,100 m. Dugong volcano is located ~60 km E of Lobster volcano, ~20 km
WNW of Niuafo’ou volcano/island, and ~680 km NE of Suva, Fiji.
Figure 2. Multibeam sonar three-dimensional (30 kHz swathmap) image of submarine volcano
Dugong. A Global Positioning System (GPS) and an Inertial Motion Unit (IMU) were used to
monitor the ship’s position and attitude. The large volcano, 45 km in diameter, is located 25 km
NW of the subaerial back-arc island volcano of Niuafo’ou. A 5 km diameter crater forms the
summit region of the volcano, with a small hydrothermal plume near its base. The mapping
revealed an enormous structure with hundreds of individual eruptive blobs and transected by
numerous faults. A dredge of the SW floor of the caldera recovered a few fresh basaltic pillow
fragments, volcanic glass, and small pieces of pumice. There is no color scale for the image for
conversion to depth, although dark blue is the deepest, trending upwards through green, yellow,
orange, red, tan, and white. Location and distance scales are also missing from the figure. Image
from CSIRO (2008b); with ancillary information from Arculus (2008).
During the 6 week research expedition in the Pacific Ocean, scientists from the Australian
National University (ANU), CSIRO Exploration & Mining, and the United States collaborated to
survey the topography of the seafloor, analyzing rock types and formations, and monitoring deep
sea hot spring activity around an area known as the North Lau Basin, 400 km NE of Fiji.
Reference: Arculus, R.J., 2008, Marine National Facility RV Southern Survey 2008
Program: Voyage Summary SS07/2008 Northern Lau Vents Expedition (NoLauVE), 23 p (URL:
http://www.cmar.csiro.au/datacentre/process/data_files/cruise_docs/SS200807sum.pdf).
CSIRO, 2008a, Active submarine volcanoes found near Fiji, CSIRO web site (URL:
http://www.csiro.au/Organisation-Structure/Divisions/Earth-Science--Resource-Engineering/Sub
marineVolcanoes.aspx).
CSIRO, 2008b, Active submarine volcanoes found near Fiji, CSIRO media release (URL:
http://www.scienceimage.csiro.au/mediarelease/mr08-93.html).
de Ronde, C.E.J, Baker, ET, Massoth, G.J, Lupton, J.E, Wright, I.C., Feely, R.A., and
Greene, R.R., 2001, Intra-oceanic subduction-related hydrothermal venting, Kermadec volcanic
arc, New Zealand, Earth and Planetary Science Letters, v. 193, p. 359-369.
Graham, I.J., Reyes, A.G., Wright, I.C., Peckett, K.M., Smith, I.E.M., and Arculus, R.J.,
2008, Structure and petrology of newly discovered volcanic centers in the northern Kermadec–
southern Tofua arc, South Pacific Ocean, Journal of Geophysical Research, v. 113, B08S02,
doi:10.1029/2007JB005453.
InterRidge Vents Database Ver. 3.1, 2013, Vent Fields (URL:
http://www.interridge.org/irvents/ventsfields?).
Keller, N.S., Arculus, R.J., Hermann, J., and Simon, R., 2008, Submarine back arc lava
with arc signature: Fonualei Spreading Center, northeast Lau Basin, Tonga, Journal of
Geophysical Research, v. 113, B08S07, doi:10.1029/2007JB005451.
Lupton, J.E., Arculus, R.J., Resing, J., Massoth, G.J., Greene, R.R., Evans, L.J., and Buck,
N., 2012, Hydrothermal activity in the Northwest Lau Backarc Basin: Evidence from water
column measurements, Geochemistry, Geophysics, Geosystems, v. 13, no. 5, doi:
10.1029/2011GC003891.
Information Contacts: Commonwealth Scientific and Industrial Research Organization
(CSIRO) (URL: http://www.csiro.au); National Oceanic and Atmospheric Agency (NOAA) (URL:
http://www.CSC.noaa.gov/crs/rs_apps/sensors/multi_beam.htm); Richard Arculus, Australian
National University Research School of Earth Sciences (Email: [email protected]);
and Frederick Stein, Director, Marine National Facility, CSIRO (Email: [email protected]).