Read a Haitian Creole translation of this web page by Susan Basen.
CLICK HERE TO VIEW THE SHIP TRACKS OVER LOIHI DURING THIS EXPEDITION (the image has been left in large format to retain details)
Preliminary Science Report Contents:
By: Frank Sansone, Fred Duennebier, and the Scientific Party An interdisciplinary team of researchers from the University of Hawaii has completed an initial study of the immediate effects of an ongoing underwater volcanic event at Loihi Seamount, 20 miles southeast of the Island of Hawaii. These researchers, in collaboration with scientists from the U.S. Geological Survey, the Bishop Museum, and the University of Washington, conducted a rapid response mission on the research ship R/V Kaimikai O Kanaloa. The ship is owned by the University of Hawaii and operated by the Hawaii Undersea Research Laboratory (one of NOAA's National Undersea Research Centers). The research cruise, sponsored by the U.S. National Science Foundation, departed August 5, and returned to Honolulu on August 10 after spending four days at the volcano. The preliminary findings of the research team are outlined below. Seismic Studies (Fred Duennebier, Nathan Becker) An over-the-side hydrophone and 24 sonobuoys were deployed to record seismic events in the summit region of Loihi. Sonobuoys are underwater microphones (hydrophones) connected to a free-floating buoy that radios signals from the hydrophone back to the ship. The over-the-side hydrophone was not used routinely, as its signals were swamped by ship noises. A variety of high frequency crackling and grinding noises, which were likely sounds of an eruption in progress, were recorded from the summit area, particularly in the area north of East Pit. In contrast, the southern flank of the seamount was seismically quiet. In addition, time-of-arrival information from sonobuoys released during a south-to-north tow-yo survey indicated the summit to be the source of these sounds. Many events were recorded on two buoys at once. Recording on more than two buoys was not common, as the strong currents tended to float the buoys off the summit area within two hours of being deployed. Digital recordings of many events located on two buoys will be used to triangulate on the source region, and hopefully localize the site of the suspected eruptive activity. Large amplitude, low frequency signals corresponding to earthquakes detected independently by the HVO seismic array, were felt by personnel on the ship during the first day of operations. These events had magnitudes of between three and four according to records at the Hawaiian Volcano Observatory. During the largest event, acoustic communication with all but one of the four permanent transponders on the ocean floor was disrupted for more than 20 minutes, recovering slowly to normal. We hypothesize that CO2 saturated water near the bottom released bubbles as a result of this shaking, and the bubbles attenuated the sound from these 12-16 KHz transducers. No earthquakes were felt after the first day. While the Pisces submersible was diving, many sounds thought to be associated with eruptive activity were recorded by sonobuoys, but the sub crews reported hearing no unusual sounds on the sub. During the first submersible dive, an ocean bottom seismometer was deployed at "Pisces peak". This seismometer should record data continuously for the next three weeks and be picked up during dives in late September. Data from this seismometer should help to constrain event locations recorded by the HVO by supplying an arrival time for many events close to the source region. Bathymetric Studies (John Smith) Multiple SeaBeam lines were run over the summit of Loihi. Although the multibeam data were of poor quality, analysis of narrow beam bathymetric data show significant changes in the summit geomorphology. Former high points, such as Pele's Vents (formerly rising to 980 m), have been replaced by pit craters hundreds of meters deep. Pele's Pit now occupies the former vent area, with a width of 260 m and a depth of 300 m. Combined submersible dive and bathymetric surveys suggest that besides new pit craters, several of the former small and large pits (East & West Pit and the Thousand Fingers depression) have collapsed and coalesced into a larger summit caldera which may still be forming. Portions of the West Pit rim are still intact while other parts have fallen away. Several of the existing pits appear to have deepened significantly. This method of caldera formation is evident on subaerial Hawaiian shield volcanoes such as Kilauea. Shipboard Water Sampling (Brian Midson, Frank Sansone) The water currents in the Loihi area are generally from the ENE to the WSW. Consequently, we ran three tow-yo sections: one, 7 km long, running S to N just west of the main north-south ridge axis; a second, 5 km long, running WSW to ENE (parallel to the current) over the summit of the seamount; and a third, 1.6 km long, running SW to NW just west of the summit. In addition, 5 hydrocasts were conducted, primarily into the pit craters at the summit. Hydrothermal fluids apparently are accumulating in the bottoms of the pit craters, as evidenced by sharp vertical temperature and salinity gradients in the CTD data, and the high particle loading in the bottom waters. The pits show inverse density profiles (the bottom water less dense than the overlying sea water) when using density values calculated from temperature and salinity data. This suggests that very high levels of particulate matter or some chemical constituent such as CO2 is causing the bottom waters to have greater density than indicated strictly from temperature and salinity relationships. CTD-measured anomalies of up to 3.5 deg C and 0.65 psu salinity were measured in the water column within the bottoms of the pit craters, with the largest anomaly in the new pit crater at the former site of Pele's Vents. Temperature anomalies of 0.5 deg C were commonly found in the water column around the summit area. Temperature anomalies of 0.1 deg C were recorded during tow-yos at distances >4 km downstream of the summit. The composition of the hydrothermal fluids appears to vary at different venting sites, as plumes and pit waters at different locations with elevated temperatures have either negative or positive salinity anomalies. This suggestion of phase separation (high salinity in water being boiled, and low salinity in steam condensates) in the vent fluids will be corroborated with other chemical data being collected. The spatial distribution of the water column plumes suggests that there is venting outside of the pit craters, most likely in the area immediately north of the East Pit. This hypothesis is supported by visual observations during the submersible dives of highly turbid water coming from this area, and the collection of glassy rock fragments on the rosette when it was inadvertently dropped on the seafloor in this area during the last tow-yo. Water Chemistry (Frank Sansone, Joe Resing, Brian Midson, Terri Rust, Betsy McLaughlin, Irena Kolotyrkina, Jim Gharib, John Lupton*, Eric DeCarlo*, Dick Feely*) The water chemistry program had two goals: (1) mapping of the extent, intensity and chemical composition of the altered sea water in hydrothermal plumes, and (2) detailed characterization of the hydrothermal vent fluids being released. In particular, we aimed to look for chemical markers that may be indicative of underwater lava extrusions and early stages of hot spot hydrothermal venting. Plume water samples were collected in Niskin bottles during tow-yo and conventional hydrocasts. Proximal plume samples were also collected with Niskins mounted on Pisces V during dives. We also had titanium majors and gas-tight samplers for vent fluid sampling during dives, but we were not able to locate any active vents. Water samples collected from above the seamount contain extremely high levels of suspended particles and chemical tracers apparently originating from an eruption, and show temperature anomalies which place them among the most volcanically altered sea water ever recorded from an undersea hydrothermal system. Water samples collected from some of the hydrothermal plumes are colored brown from the suspended particle load. The Loihi plumes sampled are very acidic. We measured pH values as low as 5.6 in plume samples from Pele's Pit that had temperature anomalies of approximately 3.0 deg C. These samples also had alkalinities as high as 3.15 meq/l, implying a TCO2 concentration of > 9 mM (roughly 4 times the concentration in sea water). Sulfide values are not available yet, but none of the plume waters recovered had a detectable sulfide smell. Dissolved gas analyses include methane and methane carbon stable isotopes, hydrogen, helium isotopes and (dissolved inorganic carbon) (DIC) and DIC stable carbon isotopes. DIC is of particular interest at Loihi because its vent fluids have previously been shown to be very enriched in DIC; samples collected on this cruise from the warmest plumes have been noticeably gassy. The results of all these measurements will not be available until after shore based analyses are complete. Dissolved Fe and Mn levels in the plumes were also very high. Shipboard analyses indicate maximum Mn levels of 0.4 uM in the plumes and 5.5 uM in Pele's Pit. Filters from the hydrocasts were clogged with particulates, at least some of which (2nd CTD) are clay particles. Shipboard analyses for Al showed unfiltered pit water concentrations an order of magnitude greater than those for background sea water. After acidification, repeated analyses of these samples showed concentrations of Al increasing continuously over time, suggesting dissolution of suspended particulate material. The mineralogy of suspended particles will be determined by X-ray diffraction and their chemistry by X-ray fluorescence (in particular, P, V, and As). Water samples will also be analyzed for inorganic nutrients by AutoAnalyzer. In addition members of the team will make low-level fluorescent measurements of dissolved ammonia and analyze for the following dissolved chemical species in the plume waters: Cu, Zn, Cd, P, V, As, Ti, and rare earth elements. Microbiological Studies (Xiyuan Wen, Betsy McLaughlin, Jim Cowen*, Marv Lilley* ) Measurements of methane oxidation rates and methane oxidation isotopic fractionation in plume samples are being conducted. Plume and background water samples were collected for determination of total bacteria numbers (epifluorescene and flow cytometry) as well as measurements of biomass (LPS). Visual observations of TEM (tunneling electron microscope) and SEM (scanning electron microscope) samples indicate that there is a tremendous number of suspended particles in the plume water. Variations in numbers of bacterial functional subpopulations will be measured using morphotype indicators by a combination of analytical transmission electron microscopy and fluorescence microscopy. Microbial methane and hydrogen oxidation rates in the plume waters are being measured. Plume water samples were preserved for DNA extractions so that preliminary estimates of the diversity of the microbial community can be obtained utilizing molecular biological techniques. Both aerobic and anaerobic media were inoculated with plume fluid samples to obtain microbial cultures for further investigation under laboratory conditions. Submersible Dives Scientists dove to the summit of Loihi seamount on Thursday, August 7, in the Pisces V manned submersible to study first hand the effects of the seismo-volcanic event (Dive P - 286). The sub landed near the highest point of the seamount (Pisces Peak) and worked its way slowly south towards the new pit crater through murky waters, with visibility less than 5 feet at times. Most of Loihi's surface consists of large broken boulders and parts of basaltic pillows. Several areas along the 2 mile route displayed fresh surfaces with newly broken pillows uncovered by large landslides or by shaking, likely due to recent earthquakes. Older surfaces are light brown while fresh surfaces are nearly black. While traversing the edge of West Pit, a previously existing pit crater on the western side of the summit, several glassy fist-sized rocks were recovered that had been thrown out of the crater together with glassy black sand grading to coarser material as the crater was approached. As this deposit is very thin and present only in a few areas, it may be the result of a landslide on the other side of West Pit that threw debris across the crater and onto the opposite rim. The freshest glassy rock samples were obtained from this crater rim. A visit to Pele's Pit, the new pit crater detected by shipboard sonar, showed that it is indeed there, and that the Pele's Vents area was destroyed by this crater-forming event. The pit is nearly filled with a cloud of murky water. West Pit, to the north of Pele's Pit, has been enlarged considerably by this activity and now connects with Pele's Pit. As the current washes across the summit from the northeast, the "smoke" in the water was believed to come from either west pit or east pit. The smoke is milky in some areas, while obviously particulate in others with cohesive globs of material. Black sand, indicative of relatively violent eruptive activity is present in patches, as is a fine white sandy material. The white material may be associated with the flox particulates in the water, and is likely to be bacterial in origin, although no samples were obtained of this material from the ocean floor. In places the white sand fills the cracks in rocks, much like a fine dusting of snow. A second dive on Friday, August 9 (Dive P - 287) also began near Pisces Peak, but then headed north along the northwestern rim of West Pit in an attempt to skirt the turbid water coming from the ENE. However, visibility remained poor, so after several hours the sub was flown across West Pit above the murky water to the NW rim of East Pit (visibility cleared at an altitude of only a few 10's of meters above the rim of the pit). The sub then descended into East Pit to collect a large number of water samples of the hydrothermally altered bottom water. The water deep in the pit was approximately three degrees warmer than normal. Rock Sampling Six volcanic rocks were collected on the first dive (Dive 286) and one rock was collected on the second dive (Dive P - 287). The rocks from Dive 286 include a very fresh sheet flow fragment with 2-3 cm thick glass rind (P286-1), several fresh, glassy pillow lobes and toes, and a hydrothermally altered glass-free flow fragment (P286-2). Based on its extremely fresh glass and its brittle, friable texture, P286-1 is judged to be the youngest sample collected. Two other samples, P286-5 and P286-6, contain slight hydrothermal coatings on fracture surfaces, but are otherwise quite fresh with 0.2-0.7 cm glassy rinds and sparse olivine phenocrysts. Sample P286-3 is a very fresh, glassy bud with up to 0.1mm glass, and little or no alteration. Sample P286-4 is a 5cm rock fragment with sparse glass and minor alteration. Preliminary analyses (Garcia) of the freshest samples show that they are tholeiites similar in composition to other Loihi tholeiites, as opposed to more alkalic rocks found on the deeper slopes of Loihi. The single rock sample from Dive 287 (P287-1) is a 4 kg pillow fragment with orange hydrothermal coating. Under the hydrothermal coating is a layer of reasonably fresh glass. A "scoop sample" of black sand-to-gravel size material was also collected (P287-2); this sample consists of freshly broken rock fragments and basaltic glass, with a small amount of hydrothermal clays and altered rock. In addition, several small glassy rock fragments were collected during the last tow-yo hydrocast imbedded in the lead at the bottom of the CTD frame. ________________________________________________________________________ Scientific Party, Affiliations, and E-mail Addresses Fred Duennebier (Chief Scientist) - Univ. Hawaii - fred@soest.hawaii.edu Frank Sansone (Co-chief Scientist) - Univ. Hawaii - sansone@soest.hawaii.edu Nathan Becker - Univ. Hawaii - nbecker@soest.hawaii.edu Jim Gharib - Univ. Hawaii - jgharib@soest.hawaii.edu Chuck Holloway - NOAA/Univ. Hawaii - holloway@soest.hawaii.edu Kevin Johnson - Bishop Museum/Univ. Hawaii - kevinj@soest.hawaii.edu Kevin Kelly - Univ. Hawaii - kevink@soest.hawaii.edu Irena Kolotyrkina - Univ. Hawaii - c/o malahoff@soest.hawaii.edu Betsy McLaughlin - Univ. Washington - betsy@ocean.washington.edu Brian Midson - Univ. Hawaii - bmidson@soest.hawaii.edu Joe Resing - Univ. Hawaii - jresing@soest.hawaii.edu Jennifer Reynolds - USGS/Hawaiian Volcano Observatory - jrr@tako.wr.usgs.gov Terri Rust - Univ. Hawaii - trust@soest.hawaii.edu John Smith - Univ. Hawaii - jrsmith@soest.hawaii.edu Xiyuan Wen - Univ. Hawaii - xwen@soest.hawaii.edu Affiliate Scientists: Alex Malahoff (UH) Marv Lilley (Univ. Washington) John Lupton (NOAA/PMEL) Jim Cowen (UH) Eric DeCarlo (UH) Ken Rubin (UH) Mike Garcia (UH) Rodey Batiza (UH) Paul Okubo (USGS - HVO) Acknowledgements: The Science Party wishes to thank all who helped make this cruise possible by responding so quickly and positively to this initiative. In particular, the many scientists who helped write the proposal, the SOEST and University administration for extremely rapid processing of the proposal, and the National Science Foundation for their nearly instantaneous review and decision. The HURL Pisces submersible crew, led by Terry Kerby, operated flawlessly, and the crew of the Kaimikai O Kanaloa, headed by Capt. Bob Hayes, helped at every step to make this cruise a success.
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