underneath the East Pacific Rise. In addition, this large-scale SEARISE survey
along the EPR allowed us to select several targets for future, more detailed studies
of volcanic and hydrothermal activities. Among these future cruises, the area that
supplied the most results to the scientific community was related to the missions
carried out on a segment of the EPR at 12°50
0 N.
After the 1980 SEARISE project, two other consecutive cruises called
‘‘CLIPPERTON’’ with the N.O JEAN CHARCOT (1981) and ‘‘Geocyatherm’’
(1982) with LE SUROIT took place. For the first time, a relatively small portion of
the East Pacific Rise near 12°50
0 N and 11°20
0 N was going to be explored in great
detail by surface ships and submersibles.
East Pacific Rise at 12°50
0 N
The East Pacific Rise (EPR) axis (at 2600 m deep) near 12°50
0 N is located
between two first order ridge discontinuities (the Orozco transform fault near 11°N
and the Siqueiros transform near 13°N), as well as between two smaller 2nd order
discontinuities, also called Overlapping Spreading Centers (OSC) at 12°43
0 N and
12°53
0 N (Fig. 7.15).
The second order discontinuities are marked by a sudden change in direction of
the axial ridge segments, and with a bending at their tips. Several sea-going
expeditions were conducted on the ridge segment at 12°50
0 N. One of the most
significant cruises that prepared the area for further diving expeditions was the
‘‘Clipperton’’ cruise, followed by the diving cruises called ‘‘Cyatherm’’ (1982) and
‘‘Geocyarise’’ (1984).
The ‘‘CLIPPERTON’’ cruise took place in 1981 and was aimed making at a
detailed exploration of a segment of the EPR where hydrothermal activity had
been detected during the previous year’s SEARISE expedition. The Clipperton
cruise began on May 9, 1981, when the NO Jean Charcot left the port of Manzanilo (Mexico) and ended on June 6 in Panama. The Jean Charcot was the largest
sea going vessel of CNEXO at the time. Its name was given in honor of the
explorer Commandant Jean-Baptiste Charcot who had explored Antarctica’s shore
in a ship called ‘‘Pourquoi Pas?’’ in 1908. The Jean Charcot, able to carry a total
of 48 crew members and scientists, was 74.5 m long, had a weight of 2200 tons
and a maximum speed of 15 kn, using a diesel-electric propulsion engine.
For the first time, I was in charge of a scientific expedition on board the R.V.
JEAN CHARCOT. This made me nervous when I arrived on board. I was going
into unknown territory and I was afraid of not being able to do a good job. I did not
know how the crew and the scientific party would accept me. The scientific party
consisted of people from different disciplines, such as water chemists from the
Centre National de Recherche Scientifique (CNRS) and scientists from the Universities of Paris 6 and 7 and from the Centre d’Energie Atomique (CEA) of
Saclay. There was a sedimentologist from Woods Hole Oceanographic Institution
and a geophysicist and structural geologist from IFREMER. However, when I
East Pacific Rise at 21°N
205
along the EPR allowed us to select several targets for future, more detailed studies
of volcanic and hydrothermal activities. Among these future cruises, the area that
supplied the most results to the scientific community was related to the missions
carried out on a segment of the EPR at 12°50
0 N.
After the 1980 SEARISE project, two other consecutive cruises called
‘‘CLIPPERTON’’ with the N.O JEAN CHARCOT (1981) and ‘‘Geocyatherm’’
(1982) with LE SUROIT took place. For the first time, a relatively small portion of
the East Pacific Rise near 12°50
0 N and 11°20
0 N was going to be explored in great
detail by surface ships and submersibles.
East Pacific Rise at 12°50
0 N
The East Pacific Rise (EPR) axis (at 2600 m deep) near 12°50
0 N is located
between two first order ridge discontinuities (the Orozco transform fault near 11°N
and the Siqueiros transform near 13°N), as well as between two smaller 2nd order
discontinuities, also called Overlapping Spreading Centers (OSC) at 12°43
0 N and
12°53
0 N (Fig. 7.15).
The second order discontinuities are marked by a sudden change in direction of
the axial ridge segments, and with a bending at their tips. Several sea-going
expeditions were conducted on the ridge segment at 12°50
0 N. One of the most
significant cruises that prepared the area for further diving expeditions was the
‘‘Clipperton’’ cruise, followed by the diving cruises called ‘‘Cyatherm’’ (1982) and
‘‘Geocyarise’’ (1984).
The ‘‘CLIPPERTON’’ cruise took place in 1981 and was aimed making at a
detailed exploration of a segment of the EPR where hydrothermal activity had
been detected during the previous year’s SEARISE expedition. The Clipperton
cruise began on May 9, 1981, when the NO Jean Charcot left the port of Manzanilo (Mexico) and ended on June 6 in Panama. The Jean Charcot was the largest
sea going vessel of CNEXO at the time. Its name was given in honor of the
explorer Commandant Jean-Baptiste Charcot who had explored Antarctica’s shore
in a ship called ‘‘Pourquoi Pas?’’ in 1908. The Jean Charcot, able to carry a total
of 48 crew members and scientists, was 74.5 m long, had a weight of 2200 tons
and a maximum speed of 15 kn, using a diesel-electric propulsion engine.
For the first time, I was in charge of a scientific expedition on board the R.V.
JEAN CHARCOT. This made me nervous when I arrived on board. I was going
into unknown territory and I was afraid of not being able to do a good job. I did not
know how the crew and the scientific party would accept me. The scientific party
consisted of people from different disciplines, such as water chemists from the
Centre National de Recherche Scientifique (CNRS) and scientists from the Universities of Paris 6 and 7 and from the Centre d’Energie Atomique (CEA) of
Saclay. There was a sedimentologist from Woods Hole Oceanographic Institution
and a geophysicist and structural geologist from IFREMER. However, when I
East Pacific Rise at 21°N
205