HighTech on the HiShSeas: Mappingthe OceanFloor

Kim Kastens and Dale Chayes

Scientists and engineersat and sea floor spreading theo- where scientists would ana- objectiveswhile still at sea. Columbia University's La- ries. Maurice Ewing, La- lyze results. Based on those The advances are not only mont-Doherty Earth Observa- mont's founder, defined the results, scientists often re- maximizing efficiency of sci- tory have designed structure of oceanic crust turned to the same areas to entific expeditions, but sophisticated computer sys- and Lamont-Doherty scien- gather additional data. To- changing the way scientists tems coupled with new ink- tists Bruce Heezen and Marie day, thanks to advancesin are organizing them. jet technology to streamline Tharp discovered the Mid- onboard computer hardware These advances have sonar mapping of the ocean Atlantic Ridge System and and software capabilities contributed to Lamont Doh- floor. Since 1949, scientists later created the first com- coupled vrith enhanced erty's standing as a global at the Lamont-Doherty Earth prehensive map of global wide-format color inkiet scientific resource. It has Observatory of Columbia ocean floor. plotting technology, com- nearly 600 scientific, techni- University have been map- In the early days, ships puter hardware and software, cal and support personnel, ping the sea floor, making would collect data at sea and scientists can collect the with 120 scientists and L00 discoveries pivotal to the de- bring them back to the Ob- data, analyze them, and ful- graduate sludents pursuing velopmentof plate tectonics servatory in Palisades,N.Y., fill many of their scientific research in the widest arrav

l-amont-Doherty'snewest research ship, the MauriceEwing.

PE&RS 1361 of the earth sciences,includ- the Maurice Ewing, em- semblesa series of nested ing geophysics,geochemis- from the early part of the barked on a cruise that boxes. First, a fairly large try, seismology,petrology, cruise are available to the sersesas an excellent exam- area at a relatively large paleontology, paleomagnet- ple shipboard scientific deci- of how the high tech ad- scale will be mapped with ics, climatology, glaciology, sion-makers in a clear and vances have dramatically multibeam sonar system and, easily digested form, in near of course, oceanogra- changed the way scientists called Hydrosweep. Basedin real phy. The Observatory'sfirst conduct time. The sophisticated researchat sea. The part on the results of the Hv- researchvessel, a converted data-handling facilities ship took an international drosweep suryey, smaller luxury yacht called the aboard the Ewing will con- team of scientists led by La- areaswill be selectedfor tribute immeasurably to car- Vema, was the first ship to mont-Doherty scientists Kim out this multi-faceted log more than 1 million Kastens and Enrico Bonatti rying cruise plan. miles of oceanographicre- to the Vema Fracture Zone The Ewing is a 239-foot, search.The secondto ac- - a ridge hundreds of kilo- 2,OOO-tonformer oil explora- complish that feat was the meters long and several kilo- tion vessel purchased from Observatory'ssecond ship, meters high whose origin is Petro the RobertD. Conrad. enigmatic. Canadaby the Observ- atory. With National In August, Lamont-Doh- The plan for the Vema Science Foundation support, it was erty's newest researchship, Fracture Zone expedition re- transformed into a sophisti- cated floating laboratory. It has a top speed of 14 knots and a cruising range of 15,000miles at 12 knots. Part of the University-Na- tional OceanographicL,abo- ratory System (UNOLS) fleet, it is available for use by sci- entists from other institu- tions and universities. Primary real-time navi- gation is provided on the Ewing by two Magnavox MX-4200 Global Positioning System (GPS)receivers. Two Magnavox T-Sets are still high-resolution imaging with available for backup, but near-bottom towed sonar and after many years of faithful for sub-bottom imaging with service, are on their way to a single-channelseismic sys- permanent retirement. A part tem. Basedin part on the re- of MagnavoxMX-11OZRS sults of the side-looking Transit satellite receivers are sonar suryey, targets will be used to provide a reality pinpointed for rock sampling check on the GPS solutions by dredging. And based on and are used as a fall-back to the results of the single- fill in the ever-decreasing channel seismic survey, tar- gaps in GPS coverage. Dur- gets will be selectedfor sedi- ing near-shore work, hyper- ment coring and for near- bolic Loran-C and RHO-RHO bottom photography using a Loran receivers are available. towed camera. but they are seldom used Thus, the execution of anJ[nore becauseof the qual- the latter parts of the cruise ity and duration of GPS. In plan will be shaped by the addition to GpS, a dual axis results from the euly parts Furuno CI-30 doppler speed of the cruise - Scientistsat work aboardship. a strategy log is used to measure the that can only work if results vessel'sspeed and course r362 relative to the water mass. Aerospace.The KSS-30 vides a sophisticatedand This high-resolution,high- emits raw gravity data via a fully supported computer update rate data is used to standardRS-232 interface. A environment with limited provide dead-reckonedfixes custom microcontroller distractions for scientists to through short gapsin GPS driven interface converts the make the most of their op- coverage.All navigation data BGM-3 signals to raw gravity portunity. is time taggedand recorded and generateASCII messages Along with developing by a Sun/SPARC-baseddata on a RS-232interface. The the computer system to han- logging system written by gravity data from either or dle the data collection and Bill Robinsonand Stephanus both sub-systemsis time imaging, Lamont-Doherty's Budhypramono. stamped and Ioggedby a technical staff was intent on The Ewing is equipped data logger. improving the hard-copy with a comprehensivesuite The earth's magnetic output. The recent acquisi- of acoustic imaging systems field is measuredwith a tion of two ENCAD NOVA- for probing into and measur- towed proton precession fET II wide-format color ing the shapeof the sea magnetometer.The BCD out- inkjet plotters has substan- floor. An Atlas Hydrosweep put is convertedto serial tially enhanced the Ewing's DS formed beam swath sonar data by a custom,microcon- capabilities. Until then, the operatingat 15.5 kilohertz troller driven interface de- ship had been equipped only measuresthe crosstrackpro- signedby foe Stennett. with two Calcomp 965 pen file of the sea floor in a This spring, Ihe Ewing plotters. swath that is twice the water switched over to its newest Although they were reli- depth in width. This profile generation data logging sys- able, they had a number of is measured to a resolution tem. The cunent system runs disadvantages.The most ob- of 1 meter and an accuracy on Sun/SPARChardware un- vious were their slow speed of about .5o/oof the water der SunOSversion 4.1. and inability to reproduce depth. Hydrosweepbathy- Basedon a process-per-data rasterimages. These had not metry is displayed in real kilowatts. The resulting data streamdesign philosophy, it really posed major problems time as a cross-profile or is displayedin real time on has a central process for dis- until computer system en- color-filled bottom map on an EPCmodel S0OOdigital tributing real-time data over hancements made the pen the systemconsole. In addi- graphic recorder. Ethernet for use by other plotters' weaknessesso con- tion, custom software appli- Vertical profiles into the workstations. The current spicuous.Scientists had to cation called MapMaker, sea floor of tens of meters to logging system is an evolved wait until they returned developedat Lamont by Wil- tens of kilometers are gener- version of one that ran on home to use more sophisti- liam B. F. Ryan and Suzanne ated using an aray of up to Masscomp hardware that cated hard-copy devices to O'Hara,is used to display 20 pneumatic sound sources was initially deployed on a view the majority of their color-shadeddata overlaid with an energy spectrum be- previous Lamont-Doherty data. by contourson any of the tween 10 hertz and 200 vessel,the R/V Conrad,in Solving the hard-copy shipboardworkstations in hertz.This seismicdata is the fall of tggo and was problem was not easy. One real time. Current efforts by receivedby and digitized in transferred to the Ewing in obvipus answer - installing O'Hara and Dave Caressat a 2DD-to 4.000-meter 1990. a $50,000electrostatic Lamont-Doherty have sub- streamer towed behind the In addition to the Sun printer - turned out to be stantially enhanced the real- ship and recorded on a Digi- and Silicon Graphicswork- impractical. The cost was time capabilities of Map- con DSS-240logging system. stations that are committed high, but the main problem Maker. The data is storedon 3480 to the real-time tasks of data was the ship's continuous High-resolutionvertical tape cartridges and can be acquisitionand logging, pitch and roll, which would profiles into the upper tens post-processedon board there are three general pur- have played havoc with the of meters of sediment on the using JDSeis,a custom soft- pose workstations available electrostatics' liquid toners. sea floor are made with an ware packagedeveloped at for onboard data processing A printer that could operate EDO WesternModel 248 3.5 Lamont by fohn Diebold. and analysis by the scientific in an unstable environment kilohertz subbottom profiler. The Ewing routinely party. Using commercial, was required. This wide-beamsounder op- measuresthe gravity field public domain, and custom- In the fall of 1992. Dale erateswith pulse widths using either a Bodenseewerk developed software in the Chayesand Dave Caressdis- from 0.1 to 3 milliseconds KSS-30 sea gravimeter or a relative peaceand quite of covered the NOVApT, the and output power of 2 to LO BGM-3 gravimeter from Bell the high seas,the ship pro- wide-format color inkiet

PE&R5 r363 plotter from ENCAD,Inc., in 139 5r,W ridge that parallels the fault 9 27S 9 27S San Diego. They evaluated separating the two plates. one at a local distributor and The origin of this ridge is were impressed enough to enigmatic. In theory, the

include two in a proposal to 9 30S 9 30S only major crustal move- the National ScienceFoun- ments at a fracture zone dation. plate boundary should be By the time the money horizontal movements. Verti- becameavailable, they were 9 33S 9 33S cal movements, capable of able to purchasethe newer building a ridge several kilo- NOVAIET II, which is the meters high, indicate that enhanced version of the NO- additional processesnot pre- 9 365 VAIET. Among NOVAIET dicted by the simple tenets II's significant improvements of plate tectonicsmust be ac- was the virtual elimination tive.

of "banding," the visible 9 39S s 39S After mapping the entire lines causedby the multiple fracture zone ridge with Hy- passesof the inkjet head. La- drosweep, the Ewing will mont-Doherty bought two use a side-looking sonar sys- NOVAIET IIs and installed tem to image a region on one r39 54W 139 51W 139 €W r39 45W r39 &W them aboard the Ewing. The flank of the fracture zone printers came through with ridge where they think that 352 583 813 1043 1273 j503 t7;3ert;ft'"';;t 2424 2654 2aa4 3114 3344 3575 flying colors during sea trials faulting has exposed deep off East the Coast and a re- Coforfill contour bathymetrymap of Dumont D'Urville,a seamount portions of the oceanic crust cently completed working in the Marquesaslsland chain in FrenchPolynesia. and upper mantle. The side- leg from Massachusettsto looking sonar instrument Iceland. NOVAJET II's out- package,developed at La- put is almost as good as an used for taking small sedi- a team led by Lamont-Doh- mont, is towed behind the electrostatic and less expen- ment cores or water samples. erty scientists will return ship on the 0.68-inch coaxial sive and producesin 10 to In July, a fourth winch aboard a Lamont-Doherty conducting cable. Constant 30 minutes a full-detail plot was added to allow use of a ship to this particular geo- adjustments of the winch are that would take a pen plotter 10,000meter coaxial con- logical feature, which was used to "fly" the instrument many hours. The NOVAfET ducing cable. Typical uses of named after Lamont's first packagea few hundred me- II's ability to make large-for- this kind of two conductor ship, the Vema. ters above the sea floor mat raster plots is a substan- cable are deep-towed acous- The Vema Fracture Zone Side-looking sonar data pro- tial aid to interpreting tic imaging sonars, sea-floor is a portion of the Mid-At- vides marine geologist with complex data setsat sea. video and still cameras,and lantic Ridge System, which the same sort of information The Ewing is presently sophisticated mid-water is the boundary between the that a land geologist would equipped with three winches sampling systems.These African and South American extract from an aerial photo- and two A-frames. All three kinds of systemstelemeter tectonics plates. At fracture graph. In this case,they of theseswinches carrying data up to the surface in real zones like Vema, the two hope to map the location 10,000meters of cable.The time as well as send power tectonic platesslide side-by- and strike of the faults that largest carries 9/16' wbe and control signals down the side past each other. The Af- accommodatedthe vertical rope, which is typically used cable. rican plate slides eastward, uplift of the fracture zone for lowering core samplers The Ewing's imaging, and the South American ridge, and the boundaries be- and dredge buckets to the mapping, and sampling facil- plate slides westward. ln tween the rock units that seafloor. A secondwinch is ities will be used extensively theory, oceanic crust is nei- were exposed by the vertical equippedwith 0.322 inch on the expedition to try to ther created nor destroyed at uplift. four-conductor cable for low- reconstruct the geological fracture zone plate bounda- On the shallowest part ering an instrument called a history of the Vema Fracture ries. of the fracture zone ridge, "CTD" that profiles conduc- Zone - halfway between The Ewing's Hydro- previous cruises have tivity and temperature of the South America and Africa, sweep swathmapping system dredged up samples of reef water column. The third just north of the equatorin will be used to map a long limestone. These rocks con- winch carries.250 inch non- the Atlantic Ocean. It seems (hundreds of kilometers), tain fossils of organisms that conducting wire and can be particularly appropriate that high (severalkilometers) lived on a shallow water reef

PE&RS 1365 a large platform or "guide- base,"which is placed on a hardrock outcrop on the sea floor. Even one meter of sed-

Color3D perspectiveimage of DumontD'Urville. within reach of sunlight. At limestone,and thus con- gravity corer. A steel tube, present,however, the water strain the breadth of the area lined with a plastic tube and depth where theselime- that was uplifted sufficiently tipped with a sharp cutting stonesoccur exceed600 me- high to reach sunlight. edge,will be driven into the ters.The interpretationis The remote sensing data sea floor by the force of a that the fracturezone ridge from the Hydrosweep, side- 2,500-poundweight. iment over the outcrop can was even shallower when looking sonar and seismic In the fall of t99+, the destabilize the guidebaseand theseorganisms lived, 9-3 systemswill be grounded- scientific drill ship JOIDES jeopardize the drilling effort. million yearsago. Following truthed by rock and sedi- Resolutionwill conduct a To locate suitable hardrock the tectonic uplift that built ment samples.To sample test of an experimental dia- outcrops, the Ewing will tow the ridge, tectonic subsid- hard rock outcrops,a steel mond coring systemon top a camera vehicle a few me- enceapparently dropped the mesh bucket, or "dredge" of the Vema FractureZone ters above the sea floor. The ridge back down to its pres- will be draggedalong the sea transverseridge. The final battery-powered towed cam- ent depth. They will use the floor on the 9/16-inchwire goal for this summer's Ewing era takes approximately Ewing's single channel se- rope. To sample the semi- cruise is to locate a suitable 1..20035mm Ektachrome ismic systemto map the ex- lithified portions of the lime- site for this test. The dia- transparencieson each cam- tent of this shallow water stonecap, they will use a mond coring system requires era tow.

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