■g-rea. flemish \ 

 _,^. r^ CAP 



MAND '"'*7''^ GRAND BANKSI f^ }^ 



^330 OF , ^ yi<r 



Figure 29. — Circled area shows planned location of international investigations of portion of 

 Mid-Atlantic Ridge. (Reproduced with the permission of the National Geographic Society.) 



Miguel in the Azores. In addition to acquiring new data on 

 processes that form the crust, there is reason to expect hy- 

 drothermal solutions to be encountered at depths of 300 to 

 600 meters. Study of these solutions and their interactions with 

 volcanic rocks could add to our knowledge of the sources of 

 metals in the earth's crust and the forces that mobilize them. 

 The Romanche Fracture Zone, which extends through the 

 equatorial Atlantic from Africa to South America, has an 

 estimated depth of 6 kilometers. Sampling at this tremendous 

 depth offers the opportunity of studying the deep crust and 

 possibly the upper mantle. E. Bonatti and K. G. V. Bostrom 

 (University of Miami) will study the alteration of these deeper 

 rocks by interaction with sea water and any sedimentary de- 

 posits located on the flanks of the Mid-Atlantic Ridge in this 

 area. 



Mid-Atlantic Ridge Bibliography 



Understanding the Mid-Atlantic Ridge, A Comprehensive Pro- 

 gram, National Academy of Sciences, Washington, D.C., 

 131 pp., 1972. 



Gulf of California Study 



The Scripps Institution of Oceanography made a multi- 

 disciplinary study of the Gulf of California during March and 



April 1972. Many scientists from different organizations and 

 many fields of study participated. Data collected during this 

 14,800-kilometer cruise (fig. 30) include coring and dredging, 

 sonobouy recorded earthquake data, heat flow measurements, 

 as well as underway measurements of bathymetry, gravity, 

 magnetics, and seismic reflection profiling. 



The gravity measurements show that the central part of 

 the Gulf of California is underlain by an oceanic crust that 

 narrows towards the north, where the effects of thick accumula- 

 tions of sediment are indicated. These results agree with pre- 

 vious work done in this area and should help to better define 

 the boundary of the oceanic crust over a broad part of the 

 Gulf. The seismic reflection and magnetic data indicate that 

 two basins within the Gulf, the Farallon and Guaymas Basins, 

 are centers of sea floor spreading. The spreading is now taking 

 place as Baja California drifts to the northwest while it sepa- 

 rates from the main America plate. Pillow basalts dredged 

 from the wall of the Salsipuedes Basin suggest that this same 

 process is occurring as far north as 29"N. Earthquakes 

 recorded on the sonobuoys showed a swarm of 50 events per 

 hour for several hours. A search in eight closed deeps in five 

 basins, using heat flow measurements, gravity cores, and revers- 

 ing thermometers, failed to reveal the presence of deep hot 

 brines similar to those found in the Red Sea. 



30 



