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rift valley but failed to do so. Years before, Dr. Clive Lister of the University of Washington observed a deficit of conductive heat release near the Mid-Ocean Ridge, which he argued supported the existence of hot springs within the axis. Scientists speculated that the Mid-Ocean Ridge owes its vertical relief to the fact that it is swollen with heat energy—that the ridge, unlike mountain ranges on land, is in essence a blister on the surface of the Earth.

Since new oceanic crust is being generated along the axis of the Mid-Ocean Ridge, it is by definition the youngest in age and for this reason should be the hottest. As the process of seafloor spreading continues with the injection of new crustal material along the ridge axis, older oceanic crust is pushed to the side, forming two giant diverging geologic conveyor belts carrying crust away from its site of creation. As it is transported away from the ridge axis, the crust slowly cools, and cooling causes the crust to contract. In essence, scientists were saying that the ridge's vertical profile represents a theoretical cooling curve.

If this hypothesis was correct, it should be possible to correlate the amount of heat coming out of the ocean floor with the distance from the ridge axis at which the measurement is made. The farther away from the ridge, the lower the heat probe reading should be. Well, this is exactly what scientists found, except, as Lister pointed out, along the axis itself. Although heat probe measurements made near the axis were high, they weren't as high as they theoretically should have been. A significant amount of heat was missing. What process was taking place along the axis of the ridge that was removing this otherwise uniformly released heat energy?

The only logical answer was hot springs. We all knew that the ridge must be underlain by magma chambers at a relatively shallow depth of 1 to 2 km. We also knew that these magma chambers contain molten rock at a temperature of 1,200 to 1,400°C. During Project FAMOUS, we discovered that the central volcanic terrain was fractured by numerous fissures and faults, which made it very permeable. Clearly, cold bottom waters within the rift valley at a temperature of 3 to 4°C could easily enter the ocean floor and must penetrate to the hot rock region surrounding the magma chambers below.

Once heated and thermally expanded, these highly enriched geothermal fluids should rise back to the surface of the rift valley floor, exiting as hot springs along its axis. But Holland's team had been unable to detect any temperature anomalies within the FAMOUS study area. Either hot springs didn't exist there at the time of the study or they didn't exist at all.

However, a growing group of marine investigators was warming to Lister's theoretical argument favoring the existence of hot springs along the axis of the Mid-Ocean Ridge. Paralleling Lister's geophysical line of reasoning was one emerging from the field of geochemistry. In 1965, Scripps graduate student Jack Corliss was completing his thesis work based upon the analysis of basaltic rock samples dredged from the Mid-Atlantic Ridge. This analysis clearly suggested that seawater was seeping downward into the newly formed ocean floor, penetrating the hot rock surrounding the magma chamber, leaching out various chemicals to form hydrothermal fluids that then flowed back to the surface of the ocean floor. The driving force of this internal circulation system was the buoyancy of the heated fluids and the tremendous geothermal gradient separating the shallow magma chamber from the cold bottom waters within the rift.

In 1975, the year after Project FAMOUS, two scientists following these two different lines of reasoning joined forces to propose an expedition to the Mid-Ocean Ridge using manned submersibles that would put these theories to test. They were Dr. Richard von Herzen formerly of the Scripps Institution of Oceanography and now at Woods Hole and Dr. Jerry van Andel also formerly of Scripps and now at Oregon State University. Van Andel had been Corliss' thesis adviser at Scripps and was well aware of his line of argument suggesting the existence of hot springs along the axis of the ridge. Von Herzen's specialty was heat flow, and he fully understood Lister's line of reasoning. Being at Woods Hole, von Herzen was keenly aware of Alvin's recent successes during Project FAMOUS. More importantly, van Andel had been one of the principal diving scientists during FAMOUS and knew first hand that Alvin was up to the challenge.

The result of this collaboration was a proposal to NSF, which had sponsored the FAMOUS Project. to search for hot springs not in the Atlantic Ocean but in the Pacific along a segment of the Mid-Ocean Ridge called the Galapagos Rift. There were several reasons for picking this site. To begin with, Oregon State University already had a large program in the Pacific called the Nazca Plate Project funded by NSF. Second, the spreading centers in the Pacific were much faster than the spreading center of the Mid-Atlantic Ridge. The faster the spreading rate, the more heat energy was being released along the ridge axis and the greater was the probability of finding hot springs.

During the subsequent cruise in the summer of 1976, a variety of instruments were used to investigate the inner rift valley of the Galapagos Rift, including sediment traps, water chemistry samplers, and the Deep Tow system from Scripps, which has a side-scan sonar and bottom camera and lighting unit. To everyone's satisfaction, the expedition succeeded in detecting temperature anomalies within the near bottom waters of the rift, which were marked by a long-term acoustic transponder.

The stage was now set for the final phrase of the program, a dive series by Alvin to pinpoint the suspected hot springs. This was scheduled to take place during the winter of 1977. Leadership for this effort was transferred from van Andel to Corliss when van Andel accepted an appointment at Stanford University. But concern over Corliss' lack of diving experience led van Andel to ask me to rake Corliss on



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