name of the scientific team to take down with us to be left on the sea floor. The
panel with its floats was carried over board by the divers and put into the arms of
the submersible. At 10h42 AM we arrived on the sea floor and looked for a good
place to install the panel. Jean-Michel Nivaggioli found a flattish surface at
3,033 m depth on top of a lobated flow and we all agreed to leave the panel there.
Jean-Michel then drove the submersible in a circle around the plastic panel in
order to take pictures before leaving the site.
Then we proceeded on our course in a westerly direction to make sure that we
were in the area with the most recent volcanism. After crossing the rift valley axis
for about 1 km, the terrain became duller looking and we noticed an increase in the
amount of sediment suggesting that we had passed beyond the most volcanically
active area of the rift valley. The dive lasted about 5 h at direct contact with the sea
floor. As we traveled along the rift valley axis, we encountered several small
volcanic constructions made up of pillow lava. They were in the middle of flatter
flows such sheet and lobated flows with a more shiny aspect and believed to be
more recent. The young flows were associated with fissures less than 2 m wide.
At 15h53, after being on the sea floor for more than 6 h, we were asked by the
ship to leave our site and return to the surface. Having covered more than 4 km on
the sea floor, with about six stops to collect rock samples and take video footage,
we felt that we had accomplished a good day’s work since we seemed to have
found the most recent active axis along the OH3 ridge segment. This would enable
the next dives in the area to proceed to other targets.
When arriving on the surface, and after setting our feet on the deck of the Nadir,
we were welcomed with glasses of champagne. The entire crew enjoyed a social
gathering that the personnel of the mess had prepared to commemorate the
Nautile’s 1,000th dive.
The next morning on September 6th, another dive (dive OT-10) was scheduled
to take place along the axis of the same OH3 ridge segment in order to complete
the information obtained during OT09 on which we had found the eruption of
sporadic recent flows along the deeper axial valley. This new dive was intended to
verify the extent of ‘‘volcanic’’ versus ‘‘tectonic’’ activities. Eulalia Gracia, a very
enthusiastic structural geologist from the Science department of the University in
Barcelona, Spain, was scheduled to dive together with Pierre Triger and Olivier
Cipriani. Eulalia was a thin, short, pretty girl with a nice smile and a very dynamic
personality. All the members of the submersible group appreciated her presence,
and they were pleased to dive with her. Because of her scheduled dive, she had to
leave the 1,000th Dive party early, in order to get a good night’s rest.
The Nautile reached the sea floor at 10h53 at a depth of 3,008 m on the first step
of the east wall. After going down several fault scarps that cut through pillow lava
terrain, they reached the rift valley floor where lobated and flat flows occur. At
11h09 (at 3,100 m) they stopped to collect their second sample on a ‘‘draperylike’’ lava flow, which had broken in situ. Moving further northward, Eulalia
observed a series of collapsed lava ponds about 3–5 m depth and less than 100 m
long which alternated between more ancient, dull looking pillow lava flows. From
wall to wall, the sea floor depth varied between 3,105 m to 3,217 m depth and the
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7 Oceanic Spreading Ridges and Sea Floor Creation
panel with its floats was carried over board by the divers and put into the arms of
the submersible. At 10h42 AM we arrived on the sea floor and looked for a good
place to install the panel. Jean-Michel Nivaggioli found a flattish surface at
3,033 m depth on top of a lobated flow and we all agreed to leave the panel there.
Jean-Michel then drove the submersible in a circle around the plastic panel in
order to take pictures before leaving the site.
Then we proceeded on our course in a westerly direction to make sure that we
were in the area with the most recent volcanism. After crossing the rift valley axis
for about 1 km, the terrain became duller looking and we noticed an increase in the
amount of sediment suggesting that we had passed beyond the most volcanically
active area of the rift valley. The dive lasted about 5 h at direct contact with the sea
floor. As we traveled along the rift valley axis, we encountered several small
volcanic constructions made up of pillow lava. They were in the middle of flatter
flows such sheet and lobated flows with a more shiny aspect and believed to be
more recent. The young flows were associated with fissures less than 2 m wide.
At 15h53, after being on the sea floor for more than 6 h, we were asked by the
ship to leave our site and return to the surface. Having covered more than 4 km on
the sea floor, with about six stops to collect rock samples and take video footage,
we felt that we had accomplished a good day’s work since we seemed to have
found the most recent active axis along the OH3 ridge segment. This would enable
the next dives in the area to proceed to other targets.
When arriving on the surface, and after setting our feet on the deck of the Nadir,
we were welcomed with glasses of champagne. The entire crew enjoyed a social
gathering that the personnel of the mess had prepared to commemorate the
Nautile’s 1,000th dive.
The next morning on September 6th, another dive (dive OT-10) was scheduled
to take place along the axis of the same OH3 ridge segment in order to complete
the information obtained during OT09 on which we had found the eruption of
sporadic recent flows along the deeper axial valley. This new dive was intended to
verify the extent of ‘‘volcanic’’ versus ‘‘tectonic’’ activities. Eulalia Gracia, a very
enthusiastic structural geologist from the Science department of the University in
Barcelona, Spain, was scheduled to dive together with Pierre Triger and Olivier
Cipriani. Eulalia was a thin, short, pretty girl with a nice smile and a very dynamic
personality. All the members of the submersible group appreciated her presence,
and they were pleased to dive with her. Because of her scheduled dive, she had to
leave the 1,000th Dive party early, in order to get a good night’s rest.
The Nautile reached the sea floor at 10h53 at a depth of 3,008 m on the first step
of the east wall. After going down several fault scarps that cut through pillow lava
terrain, they reached the rift valley floor where lobated and flat flows occur. At
11h09 (at 3,100 m) they stopped to collect their second sample on a ‘‘draperylike’’ lava flow, which had broken in situ. Moving further northward, Eulalia
observed a series of collapsed lava ponds about 3–5 m depth and less than 100 m
long which alternated between more ancient, dull looking pillow lava flows. From
wall to wall, the sea floor depth varied between 3,105 m to 3,217 m depth and the
194
7 Oceanic Spreading Ridges and Sea Floor Creation