By Joe Resing, Senior Research Scientist - JISAO University of Washington, NOAA PMEL
and Bob Embley, Geophysicist - NOAA Vents Program, Pacific Marine Environmental Laboratory
SRoF’12 operations. Map features the Northeast Lau Basin area, where the majority of cruise took place. See inset (lr) for view of all tasks. Image courtesy of Submarine Ring of Fire 2012: Northeast Lau Basin, NOAA-OER. Download larger version (jpg, 1.9 MB).
Submarine Ring of Fire 2012 Final Cruise Report (pdf, 36.2 Mb)
Given the complexity of the logistics involved in the Submarine Ring of Fire 2012 expedition, an apt summary of the cruise is “Whatever could go wrong didn’t go wrong“. Twelve dives at nine sites were successfully made, with 98.5 hours of bottom time and 164 samples for geology, chemistry, biology and microbiology. The remaining days were used for maintenance, transits and for other operations during one period of weather downtime. With the exception of a navigation issue which created some downtime during early dives, the vehicle and topside operations worked remarkably well, given that the Quest 4000 had never operated on a U.S. research vessel previously. This is a testament to the excellent cruise preparation by the Scripps Marine Operations group and the skill and cooperation of the crew of the Roger Revelle and the Quest 4000 team.
The twelve dives were each made between 8am and 9pm, local time. Normal night operations included geophysical surveys using the ship’s magnetometer, gravimeter and multibeam, and/or CTDO casts or tows mostly in the NE Lau. The geophysical surveys focused on Niuatahi, Niua and the Matas. Two new active hydrothermal sites were located during the CTDO surveys, one on the southernmost Fonualei spreading center and the second in the Mangatolu Triple Junction region. Additional targets remain in the Mangatolu Triple Junction region and our findings there suggest that the entire region contains an extraordinary amount of magmatic activity. The hydrothermal vent-endemic biology varied from site to site with species of shrimp, long-necked barnacles, mussels, snails, polychaetes and fish being the most visually obvious fauna. One type of tubeworm was found in low densities at the Niua North site.
Slideshow of highlight images corresponding to each of the ROV dives of the SRoF '12 expedition.
Vai Lili, Valu Fa Ridge, Dive Q322. A) 9/11 01-17-49: Manganese-encrusted microbial mats (black) overlaid on iron-oxide encrusted microbial mats (yellow). B) 9/11 01-17-59: Close-up of microbial mats in previous image. 1739 m. C) 9/11 03-43-33: Sulfur mats in large area of diffuse flow. 1742 m. D) 9/11 04-42-55: Using the large Davis sampler to scoop up manganese mats for DNA analysis. 1740 m. Image courtesy of Submarine Ring of Fire 2012 Exploration, NOAA Vents Program. Download image (jpg, 122 KB).
Fonualei South Dive Q323. A) 9/14 22-14-39: Toothpaste-like lava tubes near summit of central cone, ~974 m. B) 9/14 23-59-35: Manganese-coated mussel shells mark demise of venting, ~950 m, near summit of central cone. C) 9/15 00-49-02: Solitary live 'hairy' snail clings to life amongst deceased (lost their hair), near summit of central cone, ~963 m. D) 9/15 04:31-32: Venting at top of 20 m high chimney, Loloa Kakai vent field, flank of central cone, ~1550 m. Image courtesy of Submarine Ring of Fire 2012 Exploration, NOAA Vents Program. Download image (jpg, 108 KB).
Motutahi Dive Q324. A) 9/13 22-03-00: Microbially secreted mucopolysaccharide sacs on upper flank of Motutahi cone, ~1264 m. B) 9/14 02:57:56: Turbid, sulfur-rich cloud venting from pit on summit of cone, ~1244 m. C) 9/14 04-50-05: The sulfur-strewn steep slope just east of the cone summit. ~1260 m. D) 9/14 04-10-00: Lava flows with stretch marks flowing down from summit of cone, ~1259 m. Image courtesy of Submarine Ring of Fire 2012 Exploration, NOAA Vents Program. Download image (jpg, 112 KB).
Mata Ua Dive Q325. A) 9/14 22-11-58: Sedimented pillow lava tube flows on slope on south flank of Mata Ua, ~2213 m. B) 9/14 23-35-35: Sampling vesicular lavas, southern flank, ~2194 m. C) 9/15 01-30-53: Outcropping hydrothermal alteration zone, ~2135 m. D) 9/15 03-25-27: Squat lobster and lollipop sponges, northwest flank, ~2210 m. Image courtesy of Submarine Ring of Fire 2012 Exploration, NOAA Vents Program. Download image (jpg, 125 KB).
Niua South Dive Q326. A) 9/18 00-32-47: Layers of volcanic deposits outcrop on wall of the small pit, ~1158 m. B) 9/18 00-49-00: Fathead sculpin fish and shrimp in the small pit, ~1156 m. C) 9/18 04-27-00: Forest of sulfide chimneys at Adelaide sulfide structure, large pit, ~1162 m. D) Sample hot fluids with 'Major' sample bottle, Adelaide, large pit, ~1158 m. Image courtesy of Submarine Ring of Fire 2012 Exploration, NOAA Vents Program. Image courtesy of Submarine Ring of Fire 2012 Exploration, NOAA Vents Program. Download image (jpg, 133 KB).
West Mata Dive Q327. A) 9/18 21-31-35: Iron microbial mat, Mat Meadows, ~1281 m. B) 9/19 00-02-29: Truncated pillows outcrop on wall of 2010-11 Pit Crater, ~1235 m. C) 9/19 01-48-20: Shrimp swarm on pinnacle on summit of West Mata, ~1161 m. D) 9/19 07-18-00: Scale worms and polysaccharide sacs at Luo site, ~1281 m. Image courtesy of Submarine Ring of Fire 2012 Exploration, NOAA Vents Program. Download image (jpg, 121 KB).
Mata Ua Dive Q328. A) 9/20 00-18-00: Long-necked barnacle colony, ~2390 m. B) 9/20 00-41-06: OSU syringe sampling hydrothermal sediments, ~2365m. C) 9/20 01-48-18: 'Flashing' black smokers, ~2365 m. D) 9/20 05-32-39: Barnacles colonizing sulfide chimneys, ~2355 m. Image courtesy of Submarine Ring of Fire 2012 Exploration, NOAA Vents Program. Download image (jpg, 127 KB).
Mata Fitu Dive Q329. A) 9/20 23-01-21: Close-up of polychaetes on chimney, ~2605 m. B) 9/20 23-10-56: Line of active chimneys going upslope, ~2602 m. C) 9/21 03-54-00: Top of 17 m ChimE sulfide structure, ~2625 m. D) 9/21 04-59-46: Smoke pours from top of ChimE, ~2625 m. Image courtesy of Submarine Ring of Fire 2012 Exploration, NOAA Vents Program Image courtesy of Deepwater Canyons 2013 - Pathways to the Abyss, NOAA-OER/BOEM/USGS. Download image (jpg, 102 KB).
Niua North Dive Q330. A) 9/21 22-31-27: 'Hellow' sampling site, consisting of multiple sources of venting and sulfur flows. 754 m. B) 9/22 03-33-07: Vast expanse of mussels at the summit of Niua North, named 'Mussel Mania'. Low-temperature diffuse flow area with biota including paralomis crabs, eel pouts, snails, brachyuran crabs and shrimp. 722 m. C) 9/22 05-14-40: 'Hellow' area. Notice the sulfur smoke and liquid CO2 bubbles rising out of the seafloor. 747 m. D) 9/22 05-45-22: Rhyolite outcrop sampled near end of dive. The biota swarming the rocks include: shrimp, eels, and crabs. 745 m. Image courtesy of Submarine Ring of Fire 2012 Exploration, NOAA Vents Program. Download image (jpg, 118 KB).
Mata Tolu Dive Q331. A) 9/22 22-13-26 8-9 m high 'Snail' chimney from a distance. Dense biota, especially snails at the base. Samples 4-15. ~1820m. B) 9/22 22-22-25 Pagoda structures and microbial mat on Snail chimney. Biota includes Ifremieria (gray/dark brown) and Alvinochoncha (light brown, hairy) snails, polynoid worms, crabs, shrimp. C) 9/23 03-46-06 Large in-place boninite pillow lava east of the summit. Glassy outer rind sampled. ~1868 m. D) 9/23 05-54-30 Second chimney sampling site (samples 18-24), central summit. ~1840m. Image courtesy of Submarine Ring of Fire 2012 Exploration, NOAA Vents Program. Download image (jpg, 133 KB).
West Mata Dive Q332. A) 9/23 21-02-00: Truncated pillows on rim of 2010-11 Pit Crater, ~1255 m. B) 9/23 22-03-00: Shrimps swarm on young pillow tubes impinging older scarp of exposed lavas, ~1205 m. C) 9/23 23-52-26: Dike exposed in headwall area of slide, ~1220 m. D) 9/24 00-49-43: Closeup of shrimp swarm, summit of West Mata, ~1172 m. Image courtesy of Submarine Ring of Fire 2012 Exploration, NOAA Vents Program. Download image (jpg, 132 KB).
Niua South Dive Q333. A) 9/24 20-22-25: Sampling manganese oxide microbial mats in the small pit at Niua South. 1165 m. B) 9/24 21-38-58: Small active (white) and inactive (brown) chimneys on the south slope of the large pit. 1156 m. C) 9/24 22-32-40: Sulfide structure directly south of Adelaide. ~1162 m. D) 9/24 23-56-29: Target E active chimney structure on the eastern edge of the large pit. Samples 4-17 collected, ~1155m. Image courtesy of Submarine Ring of Fire 2012 Exploration, NOAA Vents Program. Download image (jpg, 132 KB).
After testing systems on a 1.5 day transit from Suva, Fiji beginning September 9, the first dive (Q-322) began as scheduled on Sept. 12. This dive had the specific objective of intensive sampling of an iron-manganese microbial ‘mat’ that had been discovered there in 2005. Dr. Bradley Tebo headed a team from Oregon Health and Sciences University (OHSU) that used specialized samplers at the site to collect several samples of the mat. On the day-long transit northward to the South Fonualei rift, two CTDO stations were completed and the multibeam system was used to collect data on unsurveyed areas.
The second dive (Q-323) on September 13 was made on the large central volcano at the southernmost end of the Fonualei Rift zone, the easternmost spreading center of the northern Lau basin. Some large spires near the summit with no hydrothermal indicators proved to be lava spines. Some active low-temperature diffuse sites and smaller chimney were sampled nearby. There was also a large bed of dead mussel shells coated with manganese that bespoke of an extensive recently active diffuse vent field. A deeper site on the NE flank was visited after a ~2-km traverse northeast and downslope through the water column. Here, the tall spires identified on a previous survey map were found to be a group of very tall (up to 30 m), active, high temperature chimneys (254°C measured).
The remaining dives of the expedition were located within the area of the Northeast Lau Basin. The first of these (Q-324) on September 14, targeted the young Motutahi cone within the large caldera of Niuatahi volcano. Previous work here showed that the cone was in a state of magmatic degassing. A degassing sulfur pit emitting diffuse fluids was discovered at the summit of the cone at ~1250 m, but there was little macrofauna in its immediate proximity. Large amounts of polysaccharide “sacs“ were observed in the peripheral area of the pit and some shrimp and polychaetes were found downslope at ~1295 m.
The September 15 dive (Q-325) was the first attempt to locate the hydrothermal system at Mata Ua volcano. The Quest-4000 searched the southern and western portion of volcano, but time ran out while surveying the NW flank where biologic indicators hinted at a large active site nearby. A CTDO tow on September 18, along the NW flank of the volcano confirmed the presence of a high-temperature site slightly deeper than where the dive had ended. Deeper exploration on September 20 (Q-328) discovered an extensive hydrothermal field on the steep slope. Prolific long-necked barnacles and other vent animals colonized the slope and older sulfide chimneys and several black smokers were discovered and sampled in a depth range of 2397-2356 m. At least two of the smokers appeared to be boiling. The maximum temperature recorded was ~360°C, but it could have been hotter (boiling at this depth would be approximately 380°C). This was the hottest site in the NE Lau to date.
The first of two dives at Niua South took place on September 18. Q-326 began in a previously unexplored small pit located near the SW corner of the southernmost large pit. Here we discovered diffuse venting in sedimented old volcanic terrain highlighted by pumice flows on the walls of the pits. After sampling the small pit we transited to the southernmost large pit and sampled one of the numerous active black smoker mounds, named Adelaide, where the dive terminated. A return dive (Q-333) on September 25 collected additional Mn-coated pumice samples for the OHSU group with their specialized tube samplers. The remainder of time on that dive was used to further explore the larger pit visited on Q-326, where numerous smoker chimneys and extinct sulfides were observed.
The dive on September 19 (Q-327) was the first at West Mata volcano since the 2009 response cruise that discovered an active eruption and took extensive observations and samples in the summit region. Samples were collected and observations made of the post-eruptive ecosystem. No sign of eruptive activity was observed during the dive, consistent with water column measurements made on the cruise. Two small hydrophones were deployed for the duration of the dive at Luo vent on the SW portion of the summit ridge, which did not record any eruption signals. A second dive (Q-332) on September 24 confirmed that the pit was fully enclosed and likely collapsed during or after the cessation of eruptive activity. The ecosystem at West Mata was dramatically changed from the relatively sparse single shrimp species population observed in 2009 to multiple species of shrimp swarming in high- density clusters over the summit region. In addition, other motile species including scale worms and crabs had colonized the volcano.
Our dive on September 21 (Q-329) explored the hydrothermal systems at Mata Fitu, the northernmost of the northern Matas. The dive started to the south of our camera line and sampled lavas in several places. Here, an unusual ridge of broken lava was interpreted to be an old fault structure. The ROV then moved upslope and discovered the first active chimney field at ~2585m. Several lines of smokers were found, two of which were quite active. The deepest site discovered on the expedition and hottest site at Mata Fitu was a 16-m high chimney, at 2644 m (base) and 331°C.
The only dive to the Niua North site took place on September 22 (Q-330). Our initial target turned out to be a sulfur pit that was similar to, but venting more intensely than, the one discovered on Q-324 on Motutahi cone. It also had a more robust biologic community on its periphery, including shrimp, solitary tubeworms, mussels, snails and other vent-endemic life. Droplets of liquid CO2 were being emitted from the pit. Diffuse venting supported the large area of mussels and other vent fauna seen on the camera tow at the summit of the ridge ~200 m from the pit. At the end of the dive a previously-mapped small ridge or dome was sampled and determined to be an outcrop of rhyolite. Additional mussel beds were found here also. Niua North, with its profuse venting of magmatic gases and sulfur volcanism, contrasts dramatically with the (presumably) more deeply “rooted“ Niua South magma source with its extensive black smoker vent fields.
The final site on the northern Matas was the summit of Mata Tolu where a dive (Q-331) was made on September 23. Mata Tolu is the shallowest of the northern Matas with a summit depth of ~1815 m and characterized by short rift zones extending southwest and northeast. The dive began ~150 m south of the summit and after obtaining some rock samples, quickly traversed to the sulfide area. The remainder of the dive mapped out the sulfide structures and obtained samples for the various disciplines. The hydrothermal area was a mixture of active and inactive structures with a maximum recorded temperature of 271°C. It appears that Mata Tolu, like Mata Fitu and Mata Ua, has had a long phase of hydrothermal activity following cessation of volcanism and development of crustal fracturing by continuing tectonic activity.
Following the end of Dive Q-333 at Niua South (above), the R/V Roger Revelle transited to Apia, Samoa. The ship arrived on the morning of September 26, marking the end of this year’s compelling and productive Submarine Ring of Fire expedition.
