1,721,071 research outputs found
Book review: Mid-Ocean ridges: dynamics of processes associated with creation of new ocean crust, edited by J.R. Cann, H. Elderfield and A. Laughton
No full textRV Atlantis Voyage 7 Leg XXX, 06 Mar – 12 Mar 2004. UK ROV Isis – engineering trials
Full text linkThis report describes the first engineering trials dives of the new UK 6500m-rated ROV Isis during Voyage 7, Leg XXX of the RV Atlantis, 6-13 March 2003. Mobilisation occurred in Jacksonville, Florida following a period of refit for the ship between March 2nd-5th and first FAT (factory-acceptance) testing was achieved on March 7th during transit from Florida to the Bahamas in ca. 850m of water. Upon arrival in Bahamian waters a swath bathymetric survey was conducted of the northeast Providence Channel immediately west of northernmost Eleuthra Island where a tongue of >4000m-deep ocean intrudes among the shelter of the Bahamas islands. Three further dives of the ROV were conducted in this area between March 8th and 11th 2003 to depths of, respectively, >2000m, >4000m and >1000m. The first two of these dives proved the extensive depth capability of the new ROV and provided first opportunity for the UK ROV team to work with the vehicle. The third dive in Bahamian waters allowed imaging of the local seafloor fauna and collection of sample material with the manipulator arms – important for proving the capability of the vehicle for demonstration to both the scientific community and the wider public in the UK following significant Government investment. Because of insurmountable bow-thruster problems aboard ship, however, dive operations had to be abandoned early on March 11th and could not be recommenced pending further dry-dock maintenance. To that end the cruise was ended ahead of schedule with the scientific party disembarking in Nassau, Bahamas, by pilot boat on Wednesday March 12th. Despite this disappointing end to the cruise three important objectives were achieved:• Preliminary FAT testing demonstrated the viability of the core system for the ROV.• Dives to >2000m were achieved (max > 4,300m) with up to 7 hours on the seafloor.• Basic seafloor imaging & sampling capabilities were demonstrated & documented
RS Bjarni Sæmundsson Cruise B8-93, 10 Jun-24 Jun 1993. Hydrothermal activity on the Reykjanes Ridge: an ODP Site survey
Full text linkFS Poseidon Cruise 240, 19 Jun-10 Jul 1998. The Fluxes at AMAR Experiment: FLAME 2
Full text linkThe principal objective of the cruise was to recover a series of 11 long-term (12 month) current meter and sediment trap moorings deployed in Summer 1997 to monitor the neutrally-buoyant hydrothermal plume overlying the Rainbow hydrothermal field on the Mid-Atlantic Ridge, near 36°15’N. Secondary objectives were to continue CTD investigations of the physical and geochemical evolution of the plume and to attempt box-coring in sedimented areas identified from TOBI sidescan sonar records beneath the dispersing neutrally buoyant plume. Mooring recovery was completely successful for all three of the sediment trap moorings with the exception that one 2-week sample was lost from one of the 5 multi-collector sediment traps deployed. Seven of the eight current meter moorings deployed were also recovered, with 100% data-recovery from the 21 current meters recovered inboard. A total of 35 CTD-nephelometer profile stations were occupied to the North and South of the Rainbow hydrothermal field, together with one background station , east of the MAR. In situ CTD and nephel data were complemented by water sampling for He-3 and CH4 and shipboard analysis of rosette samples for salinity and TDMn. A total of 4 box-cores were attempted at depths of 2400-2600m beneath the neutrally buoyant plume. All four cores were successful yielding core lengths of 43, 30, 18 and 18cm at distances of 2, 5, 12 and 29km downstream from the known hydrothermal vent-field, respectively
RRS Charles Darwin Cruise 89, 19 Aug-13 Sep 1994. Hydrothermal exploration at the Azores Triple Junction: HEAT
Full text linkHydrothermal activity on the eastern SWIR (50-70E): evidence from core-top geochemistry, 1887 and 1998
No full textEvidence for hydrothermal activity on the eastern SWIR has been reported previously in the form of optical-backscatter anomalies interpreted to indicate the presence of hydrothermal plumes. Here, I report on a brief reconnaissance analysis of the geochemical composition of core-top samples collected from sites both beneath and away from those previously-reported plume signals to determine whether evidence for fall-out of hydrothermal plume material is discernible. Samples used for this study were collected using the deep-diving submersible SHINKAI 6500 in 1998 and from the tallow-coatings applied to lead sounding lines, 111 years earlier, aboard HMS Egeria. The data indicate hydrothermal input to all but one of eight SHINKAI 6500 cores along the length of the eastern SWIR rift-valley, including the site of strongest previously reported plume anomalies. Comparison with a recent MAR study suggests that the cores analyzed here, however, may predominantly lie distant from any current or recently-active source of venting
RRS Discovery Cruise 228, 21 May-28 Jun 1997. The Fluxes at AMAR Experiment: FLAME
Full text linkThe principle objectives of the cruise were to study the physical, geochemical and biological dispersion of the neutrally-buoyant hydrothermal plume overlying the Rainbow hydrothermal field on the Mid-Atlantic Ridge, near 36°15'N; to investigate the interacting processes active within the dispersing plume; to better constrain the source of active venting on the seabed; and to quantify the physical, geochemical and biological fluxes to the water column on the segment scale. A secondary objective was to better constrain the source of strong dissolved methane concentrations which had been observed previously in the FAMOUS segment further north. An additional objective, which evolved during the course of the cruise programme, was to investigate the dispersion of vent-larvae through hydrothermal plumes along a section of the MAR extending from the Rainbow area to the previously known Lucky Strike hydrothermal field at 37°17'N. Initially, a series of hydrographic CTD stations were occupied, complete with a lowered Acoustic Doppler Current Profiler (L-ADCP) to provide instantaneous measurements of prevailing current directions with depth in the water column. This was coupled with a suite of deep-tow CTD tow-yo sections using the hydrothermal plume instrument BRIDGET. This preliminary data set yielded an understanding of the nature of plume dispersion which was then utilised to target further water column sampling using a combination of further CTD hydrocasts for water column samples, in situ filtration of particles for mineralogical, geochemical and microbiological investigations and RMT 1+8 Net trawls for biology. The strategy was largely successful and the neutrally buoyant plume, which was revealed to be dispersing under topographic control, was traced to a distance of greater than 50km down-stream. As the programme progressed a grid of closely spaced (0.5 nautical miles) orthogonal survey lines were occupied across the suspected site of venting, yielding a resolution of closest approach to the source of better than 200m. Finally at Rainbow, a suite of 8 current-meter moorings were deployed around the vent-site to monitor long-term (>12 month) fluxes of physical parameters including suspended particulate material away from the site of venting. In addition to sampling at Rainbow, 6 CTD stations were occupied in the southern portion of the FAMOUS segment and RMT 1+8 Net Trawls were completed in the Southern AMAR, AMAR, FAMOUS, North FAMOUS and Lucky Strike segments as well as in the non-transform discontinuity (NTD) offset immediately to the south of the Lucky Strike segment
Reconciling geophysical and hydrothermal data concerning the transfer of heat from the lithosphere to the oceans at fast and slow spreading-centres (abstract of paper presented at AGU Fall Meeting, San Francisco, 8-12 Dec 2003)
No full textRRS "Charles Darwin" Cruise 169, 17 Feb-19 Mar 2005. Hydrothermal exploration of the southern Mid-Atlantic Ridge
Full text linkThe principal objective of this cruise was to identify the first site or sites of high temperature hydrothermal venting anywhere on the southern Mid-Atlantic Ridge, to characterize their geological setting, preliminary chemical nature and to identify, where possible, the nature of any vent-endemic species that might inhabit such vents to investigate whether this ridge system might represent a new biogeographic province. Initially we used the TOBI deep-tow sidescan system equipped with a CTD system and optical backscatter sensors, together with Miniature Autonomous Plume Recorders (MAPRs) to identify two new sites in which diagnostic chemically- and particle-laden plumes indicated the presence of high-temperature hydrothermal venting. Subsequently, we used the ABE autonomous underwater vehicle to (1) locate the core of one of these hydrothermal plumes, (2) obtain a detailed map of the underlying seafloor and (3) photograph three discrete hydrothermal sites (2 black-smoker systems, 1 diffuse-flow) and their associated ecosystems. A series of CTD stations were occupied for water column investigations and a number of rock-coring and dredging stations were also undertaken to provide groundtruthing of sidescan sonar images of the Mid-Atlantic Ridge seafloor
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