Submarine volcanism and lava flows on the Northeast Lau Spreading Center

The following is the first Bulletin report about this submarine volcanic area in the S part of the Northeast Lau Spreading Center (NELSC) (figure 1). An informal paper by Resing and others (2009) reported that two recent eruption sites were discovered in the NE Lau Basin during a November 2008 scientific expedition aboard the research vessel RV Thompson. The first eruption site discovered was within the NELSC and contained two active submarine volcanoes, Tafu and Maka (figure 2). During the expedition a conductivity/temperature/depth (CTD)/rosette package was used to measure the physical and chemical nature of hydrothermal systems, and the Thompson's multibeam sonar provided high resolution bathymetry and seafloor backscatter imagery. Another expedition in May 2009 revealed fresh lava flows near the Maka cone.

Figure 1. Bathymetric map of NE Lau area showing two eruption areas (circled) discovered during the 2009 expedition, West Mata and NELSC where volcanoes Tafu and Maka are located. Contour interval 500 m. Inset location map shows the Fiji Islands (~ 860 km WNW) and Samoa (~ 270 km NE), along with the East Lau Spreading Center (ELSC), Central Lau Spreading Center (CLSC), and Fonulalei Spreading Center (FSC). Courtesy of Resing and others (2009).

Figure 2. Multibeam bathymetry of the Tafu-Maka ridge eruption site along the southern segment of the Northeast Lau Spreading Center (NELSC). Contour interval 100 m. Courtesy of Resing and others (2009).

Expedition during 13-28 November 2008. The Tafu-Maka eruption site was discovered on the neovolcanic zone of the southernmost segment of the NELSC at a depth of ~ 1,650 m depth (figure 1). Plumes characterized by high levels of turbidity, concentrations of volcanic glass shards, large temperature anomalies, pH anomalies, hydrogen, and methane were detected up to 800 m above the seafloor at several locations above this ridge between the Tafu and Maka features (figure 2). Volcanic glass and other clastic material were present in filtered particulate samples from the plume. Such high-rising plumes in this type of hydrographic setting have been reliable indicators of massive hydrothermal discharge associated with seafloor eruptions. The observed levels of hydrogen in plumes have only been associated with the interaction of molten rock and seawater. In addition, near-bottom temperature anomalies of ~ 0.5°C, measured with the CTDO (conductivity/temperature/depth/oxygen) package, coincided with high levels of H₂ and CH4 on the neovolcanic ridge north of Maka.

Prior work in the area (German and others, 2006) had located an intense hydrothermal plume over Maka, and this plume was relocated and sampled in 2008. According to Resing, a survey in August 2008 using a commercial ROV funded by Nautilus Minerals, Inc., discovered a very active black smoker field underlying this plume. The vent was apparently at the boiling temperature, based on video observations. The 2008 dive found no hydrothermal activity during a traverse of the presumed eruption site on the ridge axis. There were also plumes at depths below the neovolcanic ridge. Many of these plumes were probably formed by fallout and/or bottom gravity flows of volcaniclastic material such as described from the erupting submarine volcano NW Rota-1 in the Mariana arc (BGVN 31:05 and 33:02).

Ed Baker, another scientist on the 2008 expedition, observed that many more plumes were found, and much higher above the seafloor, than expected. Instruments that were lowered above the summit of Tafu, the larger of the two (which rises some 500 m above the ridge, to a depth of ~ 1,400 m), found scant evidence of activity. Above Maka, with a summit 150 m deeper at, there was a plume found at a depth of 700 m. Instruments identified distinct layers, each chemical rich, some thick, some thin, until the instruments stopped at 1,560 m depth just above the summit.

Expedition during 5-13 May 2009. Inspection with the ROV Jason during another cruise in May 2009 documented a lava flow along the NELSC, draped and folded over the seafloor near Maka, that scientists named "Puipui," meaning "curtain" in Tongan. In a blog posting on the expedition website, Ken Rubin noted that the combination of steep topography, gas-rich fluid magma, and an apparently very fast lava effusion event, created a range of lava forms over a short spatial distance. The pre-eruption land surface strongly controlled where and how the young lava flowed. Ridges of old rock less than 2 m high dammed the flow in places, where it flowed in thin flat sheets between the high ground. Nearer the volcanic vents, which appear to be located along a narrow ridge, lava cascaded 10 m or more down steep rock faces, forming lava sheets. Rubin also reported that in other places the lava ponded, crusted over, and then drained out, leaving collapse pits and revealing chambers with lava shells held up by pillars of fresh rock.

References. Falloon, T.J., Danyushevsky, L.V., Crawford, T.J., Maas, R.W., Eggins, S.M., Bloomer, S.H., Wright, D.J., Zlobin, S.K., and Stacey, A.R., 2007, Multiple mantle plume components involved in the petrogenesis of subduction-related lavas from the northern termination of the Tonga Arc and northern Lau Basin: Evidence from the geochemistry of arc and backarc submarine volcanics: Geochemistry, Geophysics, Geosystems, v. 8, Q09003, doi:10.1029/2007GC001619.

German, C.R., Baker, E.T., Connelly, D.P., Lupton, J.E.. Resing, J., Prien, R.D., Walker, S.L., Edmonds, H.N., and Langmuir, C.H., 2006, Hydrothermal exploration of the Fonualei Rift and spreading center and the North East Lau Spreading Center: Geochemistry, Geophysics, Geosystems, v. 7, Q11022, doi: 10.1029/2006GC001324.

Resing, J., Lupton, J., Embley, R., Baker, E., and Lilley, M. (compilers), 2009, Preliminary findings from the North Lau eruption sites, informal report, 2/5/09 (URL: http://www.ridge2000.org/science/downloads/email/Nlaupreliminaryfindings25.pdf).

Information Contacts: 2008 Expedition to Lau Basin (website), NOAA/PMEL VENTS Program, Hatfield Marine Science Center, 2115 S.E. OSU Dr., Newport, OR 97365, USA (URL: https://www.pmel.noaa.gov/eoi/laubasin.html); 2009 Lau Basin Eruption Exploration Expedition (blog), NOAA/PMEL VENTS Program (URL: http://laueruptions.blogspot.com/).

Information is preliminary and subject to change. All times are local (unless otherwise noted)

June 2009 (BGVN 34:06) Cite this Report

Submarine volcanism and lava flows on the Northeast Lau Spreading Center

The following is the first Bulletin report about this submarine volcanic area in the S part of the Northeast Lau Spreading Center (NELSC) (figure 1). An informal paper by Resing and others (2009) reported that two recent eruption sites were discovered in the NE Lau Basin during a November 2008 scientific expedition aboard the research vessel RV Thompson. The first eruption site discovered was within the NELSC and contained two active submarine volcanoes, Tafu and Maka (figure 2). During the expedition a conductivity/temperature/depth (CTD)/rosette package was used to measure the physical and chemical nature of hydrothermal systems, and the Thompson's multibeam sonar provided high resolution bathymetry and seafloor backscatter imagery. Another expedition in May 2009 revealed fresh lava flows near the Maka cone.

Figure 1. Bathymetric map of NE Lau area showing two eruption areas (circled) discovered during the 2009 expedition, West Mata and NELSC where volcanoes Tafu and Maka are located. Contour interval 500 m. Inset location map shows the Fiji Islands (~ 860 km WNW) and Samoa (~ 270 km NE), along with the East Lau Spreading Center (ELSC), Central Lau Spreading Center (CLSC), and Fonulalei Spreading Center (FSC). Courtesy of Resing and others (2009).

Figure 2. Multibeam bathymetry of the Tafu-Maka ridge eruption site along the southern segment of the Northeast Lau Spreading Center (NELSC). Contour interval 100 m. Courtesy of Resing and others (2009).

Expedition during 13-28 November 2008. The Tafu-Maka eruption site was discovered on the neovolcanic zone of the southernmost segment of the NELSC at a depth of ~ 1,650 m depth (figure 1). Plumes characterized by high levels of turbidity, concentrations of volcanic glass shards, large temperature anomalies, pH anomalies, hydrogen, and methane were detected up to 800 m above the seafloor at several locations above this ridge between the Tafu and Maka features (figure 2). Volcanic glass and other clastic material were present in filtered particulate samples from the plume. Such high-rising plumes in this type of hydrographic setting have been reliable indicators of massive hydrothermal discharge associated with seafloor eruptions. The observed levels of hydrogen in plumes have only been associated with the interaction of molten rock and seawater. In addition, near-bottom temperature anomalies of ~ 0.5°C, measured with the CTDO (conductivity/temperature/depth/oxygen) package, coincided with high levels of H₂ and CH4 on the neovolcanic ridge north of Maka.

Prior work in the area (German and others, 2006) had located an intense hydrothermal plume over Maka, and this plume was relocated and sampled in 2008. According to Resing, a survey in August 2008 using a commercial ROV funded by Nautilus Minerals, Inc., discovered a very active black smoker field underlying this plume. The vent was apparently at the boiling temperature, based on video observations. The 2008 dive found no hydrothermal activity during a traverse of the presumed eruption site on the ridge axis. There were also plumes at depths below the neovolcanic ridge. Many of these plumes were probably formed by fallout and/or bottom gravity flows of volcaniclastic material such as described from the erupting submarine volcano NW Rota-1 in the Mariana arc (BGVN 31:05 and 33:02).

Ed Baker, another scientist on the 2008 expedition, observed that many more plumes were found, and much higher above the seafloor, than expected. Instruments that were lowered above the summit of Tafu, the larger of the two (which rises some 500 m above the ridge, to a depth of ~ 1,400 m), found scant evidence of activity. Above Maka, with a summit 150 m deeper at, there was a plume found at a depth of 700 m. Instruments identified distinct layers, each chemical rich, some thick, some thin, until the instruments stopped at 1,560 m depth just above the summit.

Expedition during 5-13 May 2009. Inspection with the ROV Jason during another cruise in May 2009 documented a lava flow along the NELSC, draped and folded over the seafloor near Maka, that scientists named "Puipui," meaning "curtain" in Tongan. In a blog posting on the expedition website, Ken Rubin noted that the combination of steep topography, gas-rich fluid magma, and an apparently very fast lava effusion event, created a range of lava forms over a short spatial distance. The pre-eruption land surface strongly controlled where and how the young lava flowed. Ridges of old rock less than 2 m high dammed the flow in places, where it flowed in thin flat sheets between the high ground. Nearer the volcanic vents, which appear to be located along a narrow ridge, lava cascaded 10 m or more down steep rock faces, forming lava sheets. Rubin also reported that in other places the lava ponded, crusted over, and then drained out, leaving collapse pits and revealing chambers with lava shells held up by pillars of fresh rock.

References. Falloon, T.J., Danyushevsky, L.V., Crawford, T.J., Maas, R.W., Eggins, S.M., Bloomer, S.H., Wright, D.J., Zlobin, S.K., and Stacey, A.R., 2007, Multiple mantle plume components involved in the petrogenesis of subduction-related lavas from the northern termination of the Tonga Arc and northern Lau Basin: Evidence from the geochemistry of arc and backarc submarine volcanics: Geochemistry, Geophysics, Geosystems, v. 8, Q09003, doi:10.1029/2007GC001619.

German, C.R., Baker, E.T., Connelly, D.P., Lupton, J.E.. Resing, J., Prien, R.D., Walker, S.L., Edmonds, H.N., and Langmuir, C.H., 2006, Hydrothermal exploration of the Fonualei Rift and spreading center and the North East Lau Spreading Center: Geochemistry, Geophysics, Geosystems, v. 7, Q11022, doi: 10.1029/2006GC001324.

Resing, J., Lupton, J., Embley, R., Baker, E., and Lilley, M. (compilers), 2009, Preliminary findings from the North Lau eruption sites, informal report, 2/5/09 (URL: http://www.ridge2000.org/science/downloads/email/Nlaupreliminaryfindings25.pdf).

Information Contacts: 2008 Expedition to Lau Basin (website), NOAA/PMEL VENTS Program, Hatfield Marine Science Center, 2115 S.E. OSU Dr., Newport, OR 97365, USA (URL: https://www.pmel.noaa.gov/eoi/laubasin.html); 2009 Lau Basin Eruption Exploration Expedition (blog), NOAA/PMEL VENTS Program (URL: http://laueruptions.blogspot.com/).