Rea, P. 1975: Model for the formation of topographic features 

 of the East Pacific Rise, Geol. 3(2): 77-80. 



WooUard, G. P. 1975: The interrelationships of crustal and 

 upper mantle parameter values in the Pacific, Rev. Geo- 

 phys. Space Phys. 13:87-137. 



Nazca Plate Technical and Data Reports 



Handschumacher, D. W., S. T. Okamura, and P. K. Wong. 

 1975: Magnetic and bathymetric profiles from the central 

 and southeastern Pacific: 10"N-45°S, 70°W-150°W; Data 

 Report No. 29, U. of Hawaii HIG-75-18, 18 pp. text, 

 157 pp. data. 



Mid-Atlantic Ridge 



The FAMOUS (French-American Mid-Ocean Undersea 

 Study) project is a major international program to interpret 

 the geological processes occurring along mid-ocean ridges. 

 FAMOUS, which is supported in the United States by the 

 Navy, NOAA, and the National Science Foundation, is de- 

 signed to examine the Mid-Atlantic Ridge in the vicinity of the 

 Azores. The project began in 1971 with broad regional surveys. 

 These were followed by more localized studies of the Rift Valley 

 along the centerline of the rift. This preliminary work provided 

 the basis for an intensive submersible diving program on the 

 ridge during 1974. Three submersibles made 44 dives to the 

 floor of the rift valley and returned with over 1,000 kg of rock 

 samples. 



The floor of the rift valley has proven to be much more 

 complex than could be deduced from data collected from the 

 sea surface. The central part of the floor consists of a series of 

 topographic ridges and depressions running down the axis. It is 

 along the ridges that new sea floor is being created. To either 

 side of this central axial zone, marginal depressions are found 

 that result from normal faulting along tensional fractures. The 

 resulting faults and fissures show horizontal separations ranging 

 from a few centimeters to over 8 meters. The walls of the rift 

 valley are normal faults along which the floor of the valley has 

 been uplifted to the crustal ridges. Measured vertical displace- 

 ments on the faults ranged from less than 1 meter to over 100 

 meters. Volcanism appeared to be episodic and restricted to the 

 narrow central zone, but tectonic activity was evident through- 

 out the dive area and apparently is continuous. Petrologic and 

 chemical analyses of recovered basalt show a range of composi- 

 tion similar to that shown for basalts of the Atlantic Ocean as a 

 whole. The most significant variations are in the content of 

 titanium, silica, iron, magnesium, calcium, and potassium. Basalt 

 from the young axial volcanic highs tends to be low in these 

 elements, while samples from the rift valley walls show higher 

 contents of these elements. 



Mid-Atlantic Ridge Bibliography 



Hunt, M. M., W. M. Marquet, P. Moller, K. Peal, W. K. Smith, 

 and R. C. Spindel. 1974: An acoustic navigation system. 

 Woods Hole Oceanographic Institution, WHOI Ref. 74-6, 

 67 pp. 



Sigurdsson, H., and J. G. Schilling. 1976: Spinels in Mid- 

 Atlantic Ridge basalts: chemistry and occurrence. Earth 

 Planet. Sci. Lett. 29 ( 1 ) :7-20. 



Galapagos Rift Zone 



Scientists at Woods Hole Oceanographic Institution, Ore- 

 gon State University, and Scripps Institution of Oceanography 



are investigating the hydrothermal circulation along the Gala- 

 pagos Rift Zone, northeast of the Galapagos Islands. Previous 

 studies discovered anomalous bottom-water temperatures, appar- 

 ently produced by the discharge of heated water that has cir- 

 culated through the sea floor. Based on the results of an inten- 

 sive surface ship survey of the area, a diving program may be 

 proposed for the submersible Alvin. The goal of the submersible 

 program would be to sample and chemically quantify the hydro- 

 thermal fluids discharged from the sea floor. Since mixing occurs 

 rapidly with the overlying seawater, it is difficult to estimate 

 either the chemistry or temperature of the discharging fluids. 

 Direct observation and sampling from a submersible are there- 

 fore necessary to evaluate those two important parameters. 



Manganese Nodule Study 



The IDOE Manganese Nodule Program was conceived 

 during a workship at Lamont-Doherty Geological Observatory 

 in January 1972. A multi-institutional approach was recom- 

 mended to solve the long-standing questions concerning the 

 origin, distribution, and geochemistry of this unique marine 

 resource. At its inception the Manganese Nodule study involved 

 22 investigators from 13 institutions. Proposed studies were 

 organized into separate phases. 



Phase I involved compiling existing manganese nodule 

 data as a baseline for defining the future field work in the 

 program. A series of technical reports and conference pro- 

 ceedings were published as a result of Phase I activities. These 

 were reported in IDOE Progress Report Volume 4, April 1974 

 to April 1975. A project coordinator's office was also estab- 

 lished during this interval. 



Phase II of the study began in 1974 and is composed of a 

 series of cruises in an area of the northern equatorial Pacific 

 that contains extensive deposits of nodules enriched in copper 

 and nickel (fig. 18). Recovered samples have been distributed 

 to participating institutions for studies of the physical and 

 chemical structure of nodules, chemistry of sediments and inter- 

 stitial fluids, composition and structure of biogenic components, 

 rate of nodule growth, and characteristics of environments in 

 which nodules occur. Institutions currently involved in the pro- 

 gram are the University of Hawaii, Lamont-Doherty Geological 

 Observatory, Massachusetts Institute of Technology, Univer- 

 sity of Rhode Island, Scripps Institution of Oceanography, 

 University of Southern California, Washington State Univer- 

 sity, and the University of Wisconsin. 



Perhaps the most significant aspect of the program during 

 the year was the development, deployment, and recovery of an 

 ocean-bottom monitoring package. This package was deployed 

 for a period of 4 months near 11°N, 140°W. It contained a 

 camera, current meter, and nephelometer for measuring sus- 

 pended sediment concentration in the near-bottom water. A pre- 

 liminary analysis of the data reveals a noticeable variation in 

 suspended material over relatively short periods. Abundant 

 animal life is indicated in bottom photographs, but detailed 

 analysis of time-lapse photographs is necessary to determine 

 whether the organisms significantly disturb or move the nodules. 



A future activity of the program will be in-situ experiments 

 and observations from the bottom-monitoring package at sev- 

 eral locations in the Pacific. Nodule rich and nodule poor sec- 

 tions of sea floor will be compared. 



37 



