geologist from the University of Toronto, was the first to dive on the active
hydrothermal field of the Bounty volcano. Steve had come to Brest as a visiting
professor in UBO in 1994. I had heard of Steve because of his scientific reputation,
however over the years he has become a good friend since we have had many
occasions to see each other socially and share our scientific thoughts and other
ideas. Steve is a very tall man, almost 2 m in height, and he knew that he would
not be very comfortable staying for several hours inside the sphere of Nautile (only
about 2 m in diameter). Nevertheless, he was very exited to start his dive. With his
yellow jump suit half hanging over his legs and wearing his Nautile tee shirt, at
9 AM he started to climb the ladder to get to the hatch where he would descend
into the sphere. I said, ‘‘Good bye, I’ll see you this evening for a beer!’’ JeanJacques Kaioun and Pierre Guyvarch (co-pilot) accompanied Steve during his
journey.
They reached the sea floor at 10:49 at 665 m depth on top of a talus of fragmented rock debris. After climbing several vertical scarps representing a succession of lava flow fronts, at 11:50 (local time) the Nautile reached a cliff covered
with a reddish-colored hydrothermal crust. Steve was pleased to see the first sign
of hydrothermalism at 572 m depth. The first occurrence of hydrothermal material
was noted at 665 m depth. Then they found the contact between the hydrothermal
field and the volcanic rocks at 572–586 m depth, on the western flank of the
volcano. They visited two hills about 30–50 m high, which represented two volcanic eruptive centers. The hill farthest to the west was entirely covered by
ochreous colored hydrothermal deposits. Steve was particularly interested and
wanted to verify the extent of the Fe–Mn–Si oxyhydroxide deposit. The thickness
of the hydrothermal precipitates was estimated, from a previous surface coring, to
be 120 m thick. Interestingly, since the discovery of high temperature sulfide
precipitates on spreading ridge segments, the search for similar deposits on hotspot
volcanoes had been un-productive. However, we had evidence that sulfide precipitates existed inside the volcanic edifices since they had been found in veins of
volcanic rocks collected from various hotspot seamounts.
Steve Scott was the first to point out that the abundance of such deposits on
hotspot volcanoes was the result of mixing between reduced ascending sulfide-rich
fluids and descending seawater. The divers left the summit of the volcano at 18:16
and around 19:30 they were back on deck. When the pilot opened the hatch, Steve
was the first to emerge. He had a big smile and told us how fantastic it was to be
down there. In fact, he was so pleased with his dive, he had forgotten his discomfort at being in such a small space. I handed him a can of beer while a
cameramen was snapping pictures and taking video footage.
Other dives on top of the same volcano, Bounty, were programmed to make
detailed observations and to sample the active hydrothermal vents. We also tried to
make a special effort for getting water samples from the active vents. Thus dives
PN05, PN06 and PN12 were done with the participation of water chemists such as
Carl-Dieter Schonberg and Olaf Thiessen from the University of Kiel, and Gary
McMurtry, a geochemist from the University of Hawaii.
Dives on Adams and Bounty Volcanoes
335
hydrothermal field of the Bounty volcano. Steve had come to Brest as a visiting
professor in UBO in 1994. I had heard of Steve because of his scientific reputation,
however over the years he has become a good friend since we have had many
occasions to see each other socially and share our scientific thoughts and other
ideas. Steve is a very tall man, almost 2 m in height, and he knew that he would
not be very comfortable staying for several hours inside the sphere of Nautile (only
about 2 m in diameter). Nevertheless, he was very exited to start his dive. With his
yellow jump suit half hanging over his legs and wearing his Nautile tee shirt, at
9 AM he started to climb the ladder to get to the hatch where he would descend
into the sphere. I said, ‘‘Good bye, I’ll see you this evening for a beer!’’ JeanJacques Kaioun and Pierre Guyvarch (co-pilot) accompanied Steve during his
journey.
They reached the sea floor at 10:49 at 665 m depth on top of a talus of fragmented rock debris. After climbing several vertical scarps representing a succession of lava flow fronts, at 11:50 (local time) the Nautile reached a cliff covered
with a reddish-colored hydrothermal crust. Steve was pleased to see the first sign
of hydrothermalism at 572 m depth. The first occurrence of hydrothermal material
was noted at 665 m depth. Then they found the contact between the hydrothermal
field and the volcanic rocks at 572–586 m depth, on the western flank of the
volcano. They visited two hills about 30–50 m high, which represented two volcanic eruptive centers. The hill farthest to the west was entirely covered by
ochreous colored hydrothermal deposits. Steve was particularly interested and
wanted to verify the extent of the Fe–Mn–Si oxyhydroxide deposit. The thickness
of the hydrothermal precipitates was estimated, from a previous surface coring, to
be 120 m thick. Interestingly, since the discovery of high temperature sulfide
precipitates on spreading ridge segments, the search for similar deposits on hotspot
volcanoes had been un-productive. However, we had evidence that sulfide precipitates existed inside the volcanic edifices since they had been found in veins of
volcanic rocks collected from various hotspot seamounts.
Steve Scott was the first to point out that the abundance of such deposits on
hotspot volcanoes was the result of mixing between reduced ascending sulfide-rich
fluids and descending seawater. The divers left the summit of the volcano at 18:16
and around 19:30 they were back on deck. When the pilot opened the hatch, Steve
was the first to emerge. He had a big smile and told us how fantastic it was to be
down there. In fact, he was so pleased with his dive, he had forgotten his discomfort at being in such a small space. I handed him a can of beer while a
cameramen was snapping pictures and taking video footage.
Other dives on top of the same volcano, Bounty, were programmed to make
detailed observations and to sample the active hydrothermal vents. We also tried to
make a special effort for getting water samples from the active vents. Thus dives
PN05, PN06 and PN12 were done with the participation of water chemists such as
Carl-Dieter Schonberg and Olaf Thiessen from the University of Kiel, and Gary
McMurtry, a geochemist from the University of Hawaii.
Dives on Adams and Bounty Volcanoes
335