science of deep submergence - clas...

SCIENCE OF DEEP SUBMERGENCE

Daniel Fornari, Woods Hole Oceanographic Institu-tion, Geology & Geophysics Department, Clark SouthRoom 171, Mail stop d22, Woods Hole, USA

Copyright ^ 2001 Academic Press

doi:10.1006/rwos.2001.0424

Introduction

The past half-century of oceanographic research hasdemonstrated that the oceans and seaSoor hold thekeys to understanding many of the processes respon-sible for shaping our planet. The Earth’s ocean Soorcontains the most accurate (and complete) record ofgeologic and tectonic history for the past 200 mil-lion years that is available for a planet in our solarsystem. For the past 30 years, the exploration andstudy of seaSoor terrain throughout the world’soceans using ship-based survey systems and deepsubmergence platforms has resulted in unravelingplate boundary processes within the paradigm of seaSoor spreading; this research has revolutionized theEarth and oceanographic sciences. This new view ofhow the Earth works has provided a quantitativecontext for mineral exploration, land utilization,and earthquake hazard assessment, and providedconceptual models which planetary scientists haveused to understand the structure and morphology ofother planets in our solar system.

Much of this new knowledge stems from studyingthe seaSoor } its morphology, geophysical structure,and characteristics, and the chemical composition ofrocks collected from the ocean Soor. Similarly, thediscoveries in the late 1970 s of deep sea ‘blacksmoker’ hydrothermal vents at the midocean ridge(MOR) crest (Figure 1) and the chemosynthetic-based animal communities that inhabit the ventshave changed the biological sciences, provideda quantitative context for understanding globalocean chemical balances, and suggest modern ana-logs for the origin of life on Earth and extraterres-trial life processes. Intimately tied to these researchthemes is the study of the physical oceanography ofthe global ocean water masses their chemistry anddynamics, which has resulted in unprecedented per-spectives on the processes which drive climate andclimate change on our planet. These are but a fewof the many examples of how deep submergenceresearch has revolutionized our understanding ofour Earth and ocean history, and provide a glimpseat the diversity of scientiRc frontiers that await ex-

ploration in the years to come.

Enabling Deep SubmergenceTechnologies

The thing that enabled these breakthroughs was theintensive exploration that typiRed oceanographic ex-peditions in the 1950s to 1970s, and focused devel-opment of oceanographic technology andinstrumentation that facilitated discoveries on manydisciplinary levels. SigniRcant among the enablingtechnologies were satellite communication and glo-bal positioning, microchip technology and the wide-spread development of computers that could betaken into the Reld, and increasingly sophisticatedgeophysical and acoustic modeling and imagingtechniques. The other key enabling technologieswhich supplanted traditional mid-twentieth centurymethods for imaging and sampling the seaSoor fromthe beach to the abyss were submersible vehicles ofvarious types, remote-sensing instruments, andsophisticated acoustic systems designed to resolvea wide spatial and temporal range of ocean Soorand oceanographic processes.

Oceanographic science is by nature multidiscip-linary. Science carried out using deep submergencevehicles of all types has traditionally involveda wide range of research components because of thetime and expense involved with conducting Reldresearch on the seaSoor using human occupied sub-mersibles or remotely operated vehicles (ROVs) ve-hicles, and most recently autonomous underwatervehicles (AUVs) (Figures 2+6). Through the use ofall these vehicle systems, and most recently with theadvent of seaSoor observatories, deep submergencescience is poised to enter a new millennium wherescientists will gain a more detailed understanding ofthe complex linkages between physical, chemical,biological, and geological processes occurring at andbeneath the seaSoor in various tectonic settings.

Understanding the temporal dimension of seaSoorand sub-seaSoor processes will require continueduse of deep ocean submersibles and utilization ofnewly developed ROVs and AUVs for conductingtime-series and observatory-based research in thedeep ocean and at the seaSoor. These approacheswill provide new insights into intriguing problemsconcerning the interrelated processes of crustal gen-eration, evolution, and transport of geochemicalSuids in the crust and into the oceans, and origins

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SCIENCE OF DEEP SUBMERGENCE 1

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and proliferation of life both on Earth and beyond.Since the early twentieth century, people have

been venturing into the ocean in a wide range ofdiving vehicles from bathyscapes to deep diving sub-mersibles. Even in ancient times, there was writtenand graphic evidence of the human spirit seeking themysteries of the ocean and seaSoor. There is un-questionably the continuing need to take the uniquehuman visual and cognitive abilities into the oceanand to the seaSoor to make observations and facilit-ate measurements. For about the past 40 years sub-mersible vehicles of various types have beendeveloped largely to support strategic naval opera-tions of various countries. As a result of that effort,the US deep-diving submersible Alvin was construc-ted. Alvin is part of the National Deep SubmergenceFacility (NDSF) of the University National Oceano-graphic Laboratories System (UNOLS) operated bythe Woods Hole Oceanographic Institution (Figure7). Alvin provides routine scientiRc and engineeringaccess to depths as great as 4500m. The US aca-demic research community also has routine, obser-vational access to the deep ocean and seaSoor downto 6000 m depth using the ROV and tethered ve-hicles of the NDSF (Figure 7). These vehicle systemsof the NDSF include the ROV Jason, and thetethered optical/acoustic mapping systems Argo IIand DSL-120 sonar (a 120 kHz split-beam sonarsystem capable of providing 1}2 m pixel resolutionback-scatter imagery of the seaSoor and phase-bathymetric maps with &4 m pixel resolution (Fig-ure 7). These Rberoptic-based ROV and mappingsystems can work at depths as great as 6000m.

Alvin has completed over 3600 dives (more thanany other submersible of its type), and has par-ticipated in making key discoveries such as: imag-ing, mapping, and sampling the volcanic seaSoor onthe MOR crest; structural, petrological, and geo-chemical studies of transforms faults; structuralstudies of portions of deep-sea trenches off CentralAmerica; petrological and geochemical studies ofvolcanoes in back-arc basins in the western PaciRcOcean; sedimentary and structural studies of sub-marine canyons, discovering MOR hydrothermalvents; and collecting samples and making time seriesmeasurements of biological communities at hy-drothermal vents in many MOR settings in the At-lantic and PaciRc Oceans. In 1991, scientists inAlvin were also the Rrst to witness the vast biolo-gical repercussions of submarine eruptions at theMOR axis, which provided the Rrst hint that a vastsubsurface biosphere exists in the crust of the Earthon the ocean Soor (Figure 7).

Deep Submergence Science Topics

Some of the recent achievements in various Relds ofdeep submergence science include the following.

1. Discoveries of deep ocean hydrothermal commu-nities and hot ('3503C) metal-rich vents onmany segments of the global mid-ocean ridge(MOR);

2. Documentation of the immediate after-effects ofsubmarine eruptions on the northern East PaciRcRise, Axial Seamount, Gorda Ridge and CoAxialSegment of the Juan de Fuca Ridge;

3. Utilization of Ocean Drilling Program bore holesand specialized vehicle systems (e.g. Scripps Insti-tution’s Re-Entry Vehicle) (Figure 8) and instru-ment suites (e.g. CORKs) (Figure 9) for a widerange of physical properties, Suid Sow and seis-mological experiments;

4. Discoveries of extensive Suid Sow and vent-based biological communities along continentalmargins and subduction zones;

5. Initial deployment of ocean Soor observatories ofvarious types which enable the monitoring andsampling of geological, physical, biological andchemical processes at and beneath the seaSoor(Figures 10 and 11).

These studies have revolutionized our concepts ofdeep ocean processes and highlighted the need formore detailed, time-series, multidisciplinary re-search.

Within the Reld of biological oceanography, ma-jor recent advances have come from the study of thenew life forms and chemoautotrophic processes dis-covered at hydrothermal vents (Figure 10). Theseadvances have fundamentally altered biological clas-siRcation schemes, extended the known thermal andchemical limits of life, and have pushed the searchfor origins of life on Earth as well as for new lifeforms on other planetary bodies.

Recent marine biological studies show that: (1)the biodiversity of every marine community is vastlygreater than previously recognized; (2) both samp-ling statistics and molecular tools indicate that thelarge majority of marine species have not been de-scribed; (3) the complexity of biological communi-ties is far greater than previously realized; and (4)the response of various communities to both naturaland anthropogenic forcing is far more complex thanhad been understood even a decade ago. Focusedstudies over long time periods will be required tocharacterize these communities fully.

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The Reld of marine biology is heading towarda more global time-series approach as a function ofrecent discoveries largely in the photic zone of theoceans and in the deep ocean at MOR hydrothermalvents. The marine biological, chemical, and physicaloceanographic research which will be carried out inthe next decade and beyond will certainly havea profound impact on our understanding of thecomplex food webs in the ocean which control pro-ductivity at every level and have direct implicationsfor commercial harvesting of a wide range of re-sources from the ocean. Meeting the challenge ofdeciphering the various chemical, biological, andphysical inSuences on these phenomena will requirea better understanding and resolution of the causesand consequences of change on scales from hours tomillennia. Understanding ocean ecosystems andtheir constituents will improve dramatically in re-sponse to emerging molecular, chemical, optical,and acoustical technologies. Given the relative pau-city of information on deep-sea fauna in general,and especially the relatively recent discovery ofchemosynthetic ecosystems at MOR hydrothermalvents, this will continue to be a focus for deep oceanbiological research in the coming decade and be-yond. Time-series and observatory-based researchand sampling techniques will be required to answerthe myriad of questions regarding the evolution andphysiology of these unique biological systems (Fig-ures 10 and 11).

Present and future foci for deep submergencescience is MOR crests, hydrothermal systems, andthe volcano}tectonic processes that create the archi-tecture of the Earth’s crust. Geochemists from themarine geology and geophysics community have em-phasized the need for studies of: (1) the Sux-fre-quency distribution for ridge-crest hydrothermalactivity (heat, Suid, chemistry); (2) the role playedby Suid Sow in gas hydrate accumulation and deter-mination of how important hydrates are to climatechange; (3) slope stability; and (4) determination ofhow much of a role the microbial community playsin subsurface chemical and physical transforma-tions. Another focus involves subduction zone pro-cesses, including: an assessment of the Suxes ofSuids and solids through the seismogenic zone;long-term monitoring of changes in seismicity,strain, and Suid Sux in the seismogenic zone; anddetermining the nature of materials in the seis-mogenic zone.

To answer these types of questions, the marinegeology and geophysics community requires system-atic studies of temporal evolution of diverse areason the ocean Soor through research that includesmapping, dating, sampling, geophysical investiga-

tions, and drilling arrays of crustal holes (Figures 8,9 and 11). The researchers in this Reld stress thatthe creation of true seaSoor observatories at siteswith different tectonic variables, with continuousmonitoring of geological, hydrothermal, chemical,and biological activity will be necessary. Whereastraditional geological and geophysical tools willcontinue to provide some means to address aspectsof these problems, it is clear that an array of deepsubmergence vehicles, in situ sensors, and oceanSoor observatory systems will be required to addressthese topics and unravel the variations in the pro-cesses that occur over short (seconds/minutes) todecadal timescales. The infrastructural require-ments, facility, and development needs required tosupport the research questions to be asked include:a capability for long-term seaSoor monitoring; effec-tive detection and response capability for a varietyof seaSoor events (volcanic, seismic, chemical); ad-equately supported, state-of-the-art seaSoor samp-ling and observational facilities (e.g. submersible,ROVs, and AUVs), and accurate navigation systems,software, and support for shipboard integration ofdata from mutiscalar and nested surveys (Figures7B, 11 and 12).

As discussed above, the disciplines involved indeep-submergence science are varied and the scalesof investigation range many orders of magnitudefrom molecules and micrometer-sized bacteria tosegment-scales of the MOR system (10s to 100s ofkilometers long) at depths that range from 1500mto 6000m and greater in the deepest trenches.Clearly, the spectrum of scientiRc problems and en-vironments where they must be investigated requireaccess to the deep ocean Soor with a range of safe,reliable, multifaceted, high-resolution vehicles, sen-sors, and samplers, operated from support ships thathave global reach and good station-keeping capabil-ities in rough weather. Providing the right comp-lement of deep-submergence vehicles and versatilesupport ships from which they can operate, and thefunding to operate those facilities cost-effectively, isboth a requirement and a challenge for satisfyingthe objectives of deep-sea research in the comingdecade and into the twenty-Rrst century.

To meet present and future research and engineer-ing objectives, particularly with a multidisciplinaryapproach, deep submergence science will requirea mix of vehicle systems and infrastructures. Asdeep submergence science investigations extend intopreviously unexplored portions of the global sea-Soor, it is critical that scientists have access to sufR-cient vehicles with the capability to sample, observeand make time-series measurements in these envi-ronments. Submersibles, which provide the cognitive

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presence of humans and heavy payload capabilitieswill be critical to future observational, time-seriesand observatory-based research in the coming dec-ades. Fiberoptic-based ROVs and tethered systems,especially when used in closely timed, nested invest-igations offer unparalleled maneuverability, map-ping and sampling capabilities with long bottomtimes and without the limitation of human/vehicleendurance. AUVs of various designs will provideunprecedented access to the global ocean, deepocean and seaSoor without dedicated support froma surface ship.

AUVs represent vanguard technology that willrevolutionize seaSoor and oceanographic measure-ments and observations in the decades to come.Over approximately the past 5 years scientists atseveral universities and private laboratories havemade enormous advances in the capabilities andReld-readiness of AUV systems. One such system isthe Autonomous Benthic Explorer (ABE) developedby engineers and scientists at the Woods HoleOceanographic Institution (Figure 6). ABE can sur-vey the seaSoor completely autonomously and isespecially well suited to working in rugged terrainsuch as is found on the MOR. ABE maps the sea-Soor and the water column near the bottom withoutany guidance from human operators. It follows pro-grammed track-lines precisely and follows the bot-tom at heights from 5 to 30 m, depending on thetype of survey conducted. ABE’s unusual shapeallows it to maintain control over a wide range ofspeeds. Although ABE spends most of its surveytime driving forward at constant speed, ABE canslow down or even stop to avoid hitting the sea-Soor. In practice, ABE has surveyed areas in andaround steep scarps and cliffs, and not only survivedencounter with the extreme terrain, but also ob-tained good sensor data throughout the mission.

Recently ABE has been used for several geologicaland geophysical research programs on the MOR inthe north-east and south PaciRc which have furtherproved its reliability as a seaSoor survey vehicle,and pointed to its unique characteristics to collectdetailed, near-bottom geological and geophysicaldata, and to ground-truth a wide range of seaSoorterrains (Figure 12). These new perspectives on sea-Soor geology and insights into the geophysical prop-erties of the ocean crust have greatly imporved ourability to image the deep ocean and seaSoor andhave already fostered a paradigm shift in Reld tech-niques and measurements which will surely result innew perspectives for Earth and oceanographic pro-cesses in the coming decades.

Conclusions

One of the most outstanding scientiRc revelations ofthe twentieth century is the realization that oceanprocesses and the creation of the Earth’s crust with-in the oceans may determine the livability of ourplanet in terms of climate, resources, and hazards.Our discoveries may even enable us to determinehow life itself began on Earth and whether it existson other worlds. The next step is toward discove-ring the linkages between various phenomena andprocesses in the oceans and in exploring the interde-pendencies of these through time. Marine scientistsrecognize that technological advances in oceano-graphic sensors and vehicle capabilities are escala-ting at a increasingly rapid pace, and have createdenormous opportunities to achieve a scope of under-standing unprecedented even a decade ago. Thisnew knowledge will build on the discoveries in mar-ine sciences over the last several decades, many ofwhich have been made possible only through ad-vances in vehicle and sensor technology. With therapidly escalating advances in technology, marinescientists agree that the time is ripe to focus effortson understanding the connections in terms of inter-dependency of phenomena at work in the worldoceans and their variability through time.

See also

Autonomous Underwater Vehicles (AUV’s) (303).Cephalopods (195). Chemistry of HydrothermalVent Fauna (101). Deep-Sea Ridges, Microbiology(103). Deep Water Manned Submersibles (300).Mid-ocean Ridge Geochemistry and Petrology(96). Remotely Operated Vehicles (ROV’s) (302).Seamounts and Off-ridge Volcanism (97). 99.308.

Further ReadingBecker K and Davis EE (2000) Plugging the seaSoor with

CORKs. Oceanus 42(1): 14}16.Chadwick WW, Embley RW, Fox C (1995) Seabeam

depth changes associated with recent lava Sows,coaxial segment, Juan de Fuca Ridge: evidence formultiple eruptions between 1981}1993. GeophysicalResearch Letters 22: 167}170.

Chave AD, Duennebier F and Butler R (2000) PuttingH2O in the ocean. Oceanus 42(1): 6}9.

de Moustier C, Spiess FN, Jabson D et al. (2000) Deep-sea borehole re-entry with Rber optic wire line techno-logy, Proceedings 2000 of the International Sympo-sium on Underwater Technology, pp. 23}26.

Embley RW and Baker E (1999) Interdisciplinary group

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explores seaSoor eruption with remotely operated ve-hicle. Eos, Transactions of the American GeophysicalUnion, 80(19): 213, 219, 222.

Fornari DJ, Shank T, Von Damm KL et al. (1998) Time-series temperature measurements at high-temperaturehydrothermal vents, East PaciRc Rise 93 49@}51@N:monitoring a crustal cracking event. Earth and Planet-ary Science Letters 160: 419}431.

Haymon RH, Fornari DJ, Von Damm KL et al. (1993)Direct submersible observation of a volcanic eruptionon the Mid-Ocean Ridge: 1991 eruption of the EastPaciRc Rise crest at 93 45@}52@N. Earth and PlanetaryScience Letters 119: 85}101.

Humphris SE, Zierenberg RA, Mullineaux L and Thom-son R (1995) Physical, Chemical, Biological, and Geo-logical Interactions within SeaUoor HydrothermalSystems. American Geophysical Union Monograph,vol. 91.

Ryan WBF (chair) et al., (Committee on seaSoor observ-atories: challenges and opportunities) (2000) Illumina-ting the Hidden Planet, the Future of SeaUoorObservatory Science. Washington, DC: Ocean StudiesBoard, National Research Council, National AcademyPress.

Shank TM, Fornari DJ, Von Damm KL et al. (1998)Temporal and spatial patterns of biological communitydevelopment at nascent deep-sea hydrothermal ventsalong the East PaciRc Rise, 93 49.6@N}93 50.4@N. DeepSea Research, II 45: 465}515.

Tivey MA, Johnson HP, Bradley A and Yoerger D (1998)Thickness measurements of submarine lava Sows de-termined from near-bottom magnetic Reld mapping byautonomous underwater vehicle. Geophysical ResearchLetters 25: 805}808.

UNOLS (University National Laboratory System) (1994)The Global Abyss: An Assessment of Deep Submerg-ence Science in the United States. Narragansett, RI:UNOLS OfRce, Univ. of Rhode Island.

Von Damm KL (2000) Chemistry of hydrothermal ventSuids from 9}103N, East PaciRc Rise: ‘Time zero’ theimmediate post-eruptive period. Journal of Geophysi-cal Research 105: 11203}11222.



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Figure 1 Hydrothermal vents on the southern East Pacific Rise axis at depths of 2500}2800m. (A) Titanium fluid sampling bottlesaligned along the front rail of Alvin’s basket in preparation for fluid sampling. (B) Alvin’s manipulator claw preparing to sample thehydrothermal sulfide chimney. (C) View from inside Alvin’s forward-looking view port of the temperature probe being inserted intoa vent orifice to measure the fluid temperature. (D) Hydrothermal vent after a small chimney was sampled which opened up theorifice through which the fluids are exiting the seafloor. Photos courtesy of Woods Hole Oceanographic Institution } Alvin Group,D.J. Fornari and K. Von Damm and M. Lilley.



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Figure 2 (A) The submersible Alvin being lifted onto the sternof R/V Atlantis, its support ship. (B) Alvin descending to theseafloor. Photos courtesy of Woods Hole Oceanographic Institu-tion } Alvin Group and R. Catanach.

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Figure 3 (A) The ROV Jason being lifted off the stern ofa research vessel at the start of a dive. (B) ROV Jason recover-ing amphora on the floor of the Mediterranean Sea. Photoscourtesy of Woods Hole Oceanographic Institution } AlvinGroup and R. Ballard.



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Figure 4 Photographs taken from the ROV Jason at hydrothermal vents on the Mid-Atlantic Ridge near 373N on the summit ofLucky Strike Seamount at a depth of 1700 m. All photographs are of a vent named ‘Marker d4.’ (A) Overall view of vent lookingNorth. White areas are anhydrite and barite deposits, yellowish areas are covered with clumps of vent mussels. (B) Close-up of theside of the vent, Jason’s sampling basket is in the foreground. (C) Close-up view of tons mussels on the side of the hydrothermalchimney; the hydrothermal vent where hot fluids are exiting the mound is at the upper right, where the image is blurry because ofthe shimmering effect of the hot water. Nozzles of a titanium sampling bottle are at the middle-right edge. (D) Insertinga self-recording temperature probe into a beehive chimney. (E) Titanium fluid sampling bottles being held by Jason’s manipulatorduring sampling. (F) Close-up of nozzles of sampling bottle inserted into vent orifice during sampling. Photos (D)-(F) are framegrabs of Jason video data. Photos courtesy of Woods Hole Oceanographic Institution } ROV Group, D.J. Fornari, S. Humphris, andT. Shank.



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Figure 5 (A) ROV Tiburon of the Monterey Bay AquariumResearch Institute (MBARI) in the hanger of its support ship R/VWestern Flyer. This electric-powered ROV can dive to 4000 m.A steel-armored, electro-optical cable connects Tiburon to theR/V Western Flyer and delivers power to the vehicle. Electricthrusters allow fine maneuvering while minimizing underwaternoise and vehicle disturbance. A variable buoyancy control sys-tem, together with the syntactic foam pack, enables Tiburon tohover inches above the seafloor without creating turbulence, topick up a rock sample, or maneuver quickly to follow an animal.(B) ROV Ventana of the MBARI being launched from its supportship R/V Pt. Lobos. This ROV gives researchers the opportunityto make remote observations of the seafloor to depths of1850 m. The vehicle has two manipulator arms } a seven-func-tion arm with five spatially correspondent joints and anotherseven-function robot arm with six spatially correspondent joints.Both arms can use a variety of end effectors to suit the type ofwork being done. Ventana is also equipped with a conductivity,temperature and density (CTD) package including a dissolved-oxygen sensor and a transmissometer. Photos courtesy ofMBARI.

Figure 6 The autonomous underwater vehicle (AUV) ABE(Autonomous Benthic Explorer) of the Woods Hole Oceano-graphic Institution’s Deep Submergence Laboratory, which cansurvey the seafloor completely autonomously to depths upto4000 m and is especially well suited to working in rugged terrainsuch as is found on the Mid Ocean Ridge. Photo Courtesy ofWoods Hole Oceanographic Institution. Photo courtesy ofWHOI.



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Figure 7 (A) Summary of the US National Deep Submergence Facility (NDSF) vehicles operated for the University NationalOceaographic Laboratories System (UNOLS) by the Woods Hole Oceanographic Institution (WHOI). (B) Montage of the NDSFvehicles showing examples of the various types of data they collect. The figure also shows the nested quality of the surveysconducted by the various vehicles which allows scientists to explore and map features with dimensions of tens of kilometers (topright multibeam sonar map), to detailed sonar back scatter and bathymetry swaths which have pixel resolution of 1}2 m (DSL-120sonar), which are then further explored with the Argo II imaging system, or sampled using Alvin or ROV Jason. Graphics by P.Oberlander, WHOI; photos courtesy of WHOI } Alvin and ROV Group.



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Figure 8 (A) The Scripps Institution of Oceanography’s Con-trol Vehicle is a specialized ROV that can place instrumentstrings inside deep-sea boreholes, using a conventional oceano-graphic vessel capable of dynamic positioning and equippedwith a winch carrying 17.3 mm (0.68 in ) electromechanical cablewith a single coax (RG8-type). The control vehicle is 3.5 m talland weighs about 500 kg in water (1000 kg in air). It consists ofa stainless-steel frame that contains two orthogonal horizontalhydraulic thrusters, a compass, a Paroscientific pressure gauge,four 250 W lights, a video camera, sonar systems, electronicinterfaces to electrical releases and to a logging probe, andelectronics to control all these sensors and handle data telem-etry to and from the ship. Telemetry on the tow cable’s singlecoax is achieved by analog frequency division multiplexing overa frequency band extending from 20 kHz to about 800 kHz. Thesonars include a 325kHz sector-scanning sonar, a 23.5 kHznarrow beam acoustic altimeter, and a 12 kHz sonar for longbaseline acoustic navigation. This system was used success-fully in the 1998 Ocean Seismic Network Pilot Experiment atODP Hole 843B, 225 km south-west of the island of Oahu,Hawaii. In 1999, the Control Vechicles analog telemetry modulewas converted into a digital system using fiberoptic technologythus providing bandwidth capabilities in excess of 100 Mbaud.(B) Cartoon showing the configuration of the control vehicledeployed from a research ship as it enters an Ocean DrillingProgram bore hole to insert an instrument string. Photo anddrawing courtesy of Scripps Institution of Oceanography } Mar-ine Physical Laboratory, F. Spiess, and C. de Moustier.



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Figure 9 (A) Diagram of the upper portion of an Ocean Drill-ing Program (ODP) borehole with a Circulation Obviation Ret-rofit Kit (CORK) assembly. These units serve the same purposeas a ‘cork’ which seals a bottle; in the deep-sea case, the bottleis the seafloor which contains fluids that are circulating in theocean crust. The CORK allows scientists to access the circula-ting fluids and make controlled hydrologic measurements of thepressures and physical properties of the fluids. (B) A CORKobservatory on the ocean floor in ODP hole 858G off the Pacificnorth-west coast. (C) A CORK with instruments installed tomeasure sub-seafloor fluid circulation processes. Diagram cour-tesy of Woods Hole Oceanographic Institutions and J. Doucette;photo courtesy of K. Becker and E. Davis.

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Figure 10 Time-series sequence of photographs taken of the same area of seafloor from the submersible Alvin of a hydrothermalvent site on the East Pacific Rise axis near 93 49.8@N at a depth of 2500 m. (A) ‘Snow blower’ vent spewing white bacterialby-product during the 1991 eruption. (B) Same field of view as (A) about 9 months later. Diffuse venting is still occurring as isbacterial production. White areas in the crevices of the lava flow are juvenile tube worms. (C) Patches of Riftia tube wormscolonizing the vent area &18 months after the March 1991 eruption. (D) Tube worm community has continued to develop, and theventing continues over 5 years after the eruption. (E) Close-up photograph of zoarcid vent fish (middle-left), tube worms, mussels(yellowish oblong individuals) and bathyurid crab (center). (F) A time-series temperature probe (with black and yellow tape),deployed at a hydrothermal vent (Tube worm pillar) on the East Pacific Rise crest near 93 49.6@N at a depth of 2495 m. The vent issurrounded by a large community of tube worms. (G) Seafloor markers along the Bio-Geo Transect, a series of 210 markers placedon the seafloor in 1992 to monitor the changes in hydrothermal vent biology and seafloor geology over a 1.4 km long section of theEast Pacific Rise axis that have occurred after the 1991 volcanic eruption at this site. Photographs courtesy of T. Shank, WoodsHole Oceanographic Institution and R. Lutz, Rutgers University, D.J. Fornari and Woods Hole Oceanographic Institution } AlvinGroup.

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Figure 11 (A) Diagram of the deployment of the Hawaii-2 Observatory (H2O) one of the first long-term, deep seafloorobservatories deployed in the past few years. Scientists used the ROV Jason to splice an abandoned submarine telephone cableinto a termination frame which acts as an undersea telephone jack. Attached by an umbilical is a junction box, which serves as anelectrical outlet for up to six scientific instruments. An ocean bottom seismometer and hydrophone are now functioning at thisobservatory. (B) The H2O junction box as deployed on the seafloor and photographed by ROV Jason. Drawing courtesy of JayneDoucette, Woods Hole Oceanographic Institution (WHOI), A. Chave, and WHOI}ROV group.



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Figure 12 (A) Bathymetry map (contour interval 10 m) showing location of 1993 CoAxial lava eruption (gray) on the Juan de FucaRidge off the coast of Washington, and ABE tracklines (each color is a separate dive). (B) Magnetic field map based on ABEtracklines showing strong magnetic field over new lava flow. (C) Computed lava flow thickness assuming an average lavamagnetization of 60 A/m compared with (D) lava flow thickness determined from differential swath bathymetry Figure courtesy of M.Tivey, Woods Hole Oceanographic Institution.



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