Four days after this incident, another dive was programmed to go back to the
same place as dive C-5 in order to investigate the impact of Archmède on the
bottom sediment. Dive C-7 was made by Xavier Le Pichon and Jean Jarry with
Gilbert de Froberville as pilot. The report of the dive and their observations were
written in an article published in Earth and Planetary Science Letters (LePichon
et al. 1975).
Since the transponder field had been left at the site, the submersible did not
have any problem finding the impact area. They arrived at 2,500 m depth and
made a first pass at 30 m above the impact zone in order to make a profile with an
echo sounder, which is a mud penetrator, and which helped to measure the
thickness of the sediment. They descended further down, and maintained visual
contact for their observations and to take pictures. They crossed the sedimentary
ridges parallel to the contour line of the slope that the previous dive C-5 had hit.
Further down slope they found the zone of impact and the disturbed sediment
(Fig. 7.3). These sedimentary ridges were probably 10 m thick and may have been
hundreds of meters long. They had a rughose and folded appearance when compared to the surrounding, whiter and undisturbed sediment. The whiter finegrained sediment was incidentally burrowed by animal dwellers. This sedimentary
horizon was partially covered by darker, coarser-grained and reworked sediment.
Thus it was interpreted that natural, gravitational slumping producing avalanches
of unstable sedimentary layers along the continental slope had been the cause of
producing the elongated sedimentary ridges we first observed. When Archimède
hit the summit of one of these unstable sedimentary ridges, this triggered an
avalanche that caught and trapped the submersible on the sea floor.
Diving near Toulon
Prior to our Project FAMOUS dives in the middle of the Atlantic, it was also
decided by the submersible team based at La Seynes, near Toulon on the Mediterranean Sea, that we should undertake a few dives in the diving saucer Cyana,
near their base. My first dive was in the port of Toulon at about 10 m depth in a
dirty and muddy environment. This was probably a test to see if I suffered from
claustrophobia. The next day, we went off the coast of Toulon to dive near the
Island of Porqueroles. Raymond Kentzy, nicknamed ‘‘Canoë’’, who was the senior
pilot of the Cyana submersible team, piloted this dive. Kentzy used to be a pilot on
the diving saucer that Jacques Cousteau had used with the Research Vessel
CALYPSO. He was an excellent, well-trained pilot, and I trusted him with my life.
Canoë was a relatively short, thickset man with short hair and a constant smile
on his face. He also appeared to have considerable strength. On this dive, there
were only the two of us on board the small submersible: Canoë and Roger in the
Cyana, diving on the continental slope at less than 70 m depth. We reached bottom
quickly after our launch from the support ship, Nadir. As soon as we arrived on the
bottom, Kentzy blasted off at full speed above the sediment and suddenly we
180
7 Oceanic Spreading Ridges and Sea Floor Creation
same place as dive C-5 in order to investigate the impact of Archmède on the
bottom sediment. Dive C-7 was made by Xavier Le Pichon and Jean Jarry with
Gilbert de Froberville as pilot. The report of the dive and their observations were
written in an article published in Earth and Planetary Science Letters (LePichon
et al. 1975).
Since the transponder field had been left at the site, the submersible did not
have any problem finding the impact area. They arrived at 2,500 m depth and
made a first pass at 30 m above the impact zone in order to make a profile with an
echo sounder, which is a mud penetrator, and which helped to measure the
thickness of the sediment. They descended further down, and maintained visual
contact for their observations and to take pictures. They crossed the sedimentary
ridges parallel to the contour line of the slope that the previous dive C-5 had hit.
Further down slope they found the zone of impact and the disturbed sediment
(Fig. 7.3). These sedimentary ridges were probably 10 m thick and may have been
hundreds of meters long. They had a rughose and folded appearance when compared to the surrounding, whiter and undisturbed sediment. The whiter finegrained sediment was incidentally burrowed by animal dwellers. This sedimentary
horizon was partially covered by darker, coarser-grained and reworked sediment.
Thus it was interpreted that natural, gravitational slumping producing avalanches
of unstable sedimentary layers along the continental slope had been the cause of
producing the elongated sedimentary ridges we first observed. When Archimède
hit the summit of one of these unstable sedimentary ridges, this triggered an
avalanche that caught and trapped the submersible on the sea floor.
Diving near Toulon
Prior to our Project FAMOUS dives in the middle of the Atlantic, it was also
decided by the submersible team based at La Seynes, near Toulon on the Mediterranean Sea, that we should undertake a few dives in the diving saucer Cyana,
near their base. My first dive was in the port of Toulon at about 10 m depth in a
dirty and muddy environment. This was probably a test to see if I suffered from
claustrophobia. The next day, we went off the coast of Toulon to dive near the
Island of Porqueroles. Raymond Kentzy, nicknamed ‘‘Canoë’’, who was the senior
pilot of the Cyana submersible team, piloted this dive. Kentzy used to be a pilot on
the diving saucer that Jacques Cousteau had used with the Research Vessel
CALYPSO. He was an excellent, well-trained pilot, and I trusted him with my life.
Canoë was a relatively short, thickset man with short hair and a constant smile
on his face. He also appeared to have considerable strength. On this dive, there
were only the two of us on board the small submersible: Canoë and Roger in the
Cyana, diving on the continental slope at less than 70 m depth. We reached bottom
quickly after our launch from the support ship, Nadir. As soon as we arrived on the
bottom, Kentzy blasted off at full speed above the sediment and suddenly we
180
7 Oceanic Spreading Ridges and Sea Floor Creation