recent volcanism had occurred elsewhere, such as at the margin of the rift valley.
The bathymetric map showed a sub-circular volcanic edifice located on the western edge of the rift valley and we decided to explore it during the first year of the
project.
On the morning of September 4, 1973, dive AR 73-13 took place with Gilbert
Harismendy as the pilot, Jean-Louis Michel as the engineer, and I was the scientific observer. As the Archimède sank down, Michel was busy communicating
with the surface ship using the underwater telephone called ‘‘TUX’’ in order to get
a fix with respect to the transponders sitting on the sea floor. The transponder was
at an altitude of 523 m above the sea floor and at a depth of 2,000 m, as indicated
according to the pressure gauge. The continuous positioning of the bathyscaphe
every 300 m as it sank allowed us to relocate ourselves with respect to the transponders moored on the sea floor.
When we arrived near the bottom, about 300 m above the sea floor (or in other
words, at 2,294 m depth below the sea surface) we were able to see something on
the radar screen. It was a semi-circular scarp about 200 m away from us in the
direction of 143° N. It was 10:05, we were at the bottom at 2,636 m depth and as
Archimède approached the sea floor, it stirred up a lot of powdery sediment, so the
water outside the porthole was cloudy. The cloudy water blocked our visibility, so
we couldn’t see much until the current had cleared away the sediment. We landed
on a scarp and on the starboard side I could only see water. The slope was on the
port side so Harismendy was able to observe a tubular flow of solidified lava
oriented down slope. The large lava tubes were about 2 m in diameter and partially
buried by sediment. The pilot reoriented the submersible along the side of the
slope in order that I could have better visibility of the sea floor from my porthole. I
saw that we were in a field of pillow lavas that were partially buried by sediment
(\15 %). Based on the surface morphology and the presence of some sponges
growing on the lava flow, it appeared obvious that volcanic activity on this
structure had ceased a long time ago.
As we stopped for sampling, the current pushed us away from our target and the
pilot started the engine to re-position the submarine, thereby stirring up a lot of
sediment and hence losing visibility once again. He had to wait until our visibility
was restored before attempting the sampling operation. In the meantime, I took
pictures of the site and described the lava flow in my hand-held tape recorder. At
2,637 m depth I noticed a scarp in front of us, and took a picture. The bottom had
become rough with giant pillow lava filling up the field of view. Then we crossed a
depression and noted that the direction of the flow followed the depression as if the
lava had been pouring along a riverbed. After about 30 min, we had traveled
300 m and a strong reflector on the radar screen indicated the presence of a major
linear scarp running in the direction of 010–2108, parallel to the ridge axis. The
area was highly fractured with collapsed blocks. No recent lava was observed so I
was pretty sure that we were no longer on the volcanically active zone. The
structure we had visited was an ancient volcanic edifice that had been completely
dismantled by tectonic activity. The area appeared chaotic with tall, nearly vertical
cliffs. I named the area ‘‘Mount Jupiter’’.
Diving on the Mid-Atlantic Ridge in the FAMOUS Area
185
The bathymetric map showed a sub-circular volcanic edifice located on the western edge of the rift valley and we decided to explore it during the first year of the
project.
On the morning of September 4, 1973, dive AR 73-13 took place with Gilbert
Harismendy as the pilot, Jean-Louis Michel as the engineer, and I was the scientific observer. As the Archimède sank down, Michel was busy communicating
with the surface ship using the underwater telephone called ‘‘TUX’’ in order to get
a fix with respect to the transponders sitting on the sea floor. The transponder was
at an altitude of 523 m above the sea floor and at a depth of 2,000 m, as indicated
according to the pressure gauge. The continuous positioning of the bathyscaphe
every 300 m as it sank allowed us to relocate ourselves with respect to the transponders moored on the sea floor.
When we arrived near the bottom, about 300 m above the sea floor (or in other
words, at 2,294 m depth below the sea surface) we were able to see something on
the radar screen. It was a semi-circular scarp about 200 m away from us in the
direction of 143° N. It was 10:05, we were at the bottom at 2,636 m depth and as
Archimède approached the sea floor, it stirred up a lot of powdery sediment, so the
water outside the porthole was cloudy. The cloudy water blocked our visibility, so
we couldn’t see much until the current had cleared away the sediment. We landed
on a scarp and on the starboard side I could only see water. The slope was on the
port side so Harismendy was able to observe a tubular flow of solidified lava
oriented down slope. The large lava tubes were about 2 m in diameter and partially
buried by sediment. The pilot reoriented the submersible along the side of the
slope in order that I could have better visibility of the sea floor from my porthole. I
saw that we were in a field of pillow lavas that were partially buried by sediment
(\15 %). Based on the surface morphology and the presence of some sponges
growing on the lava flow, it appeared obvious that volcanic activity on this
structure had ceased a long time ago.
As we stopped for sampling, the current pushed us away from our target and the
pilot started the engine to re-position the submarine, thereby stirring up a lot of
sediment and hence losing visibility once again. He had to wait until our visibility
was restored before attempting the sampling operation. In the meantime, I took
pictures of the site and described the lava flow in my hand-held tape recorder. At
2,637 m depth I noticed a scarp in front of us, and took a picture. The bottom had
become rough with giant pillow lava filling up the field of view. Then we crossed a
depression and noted that the direction of the flow followed the depression as if the
lava had been pouring along a riverbed. After about 30 min, we had traveled
300 m and a strong reflector on the radar screen indicated the presence of a major
linear scarp running in the direction of 010–2108, parallel to the ridge axis. The
area was highly fractured with collapsed blocks. No recent lava was observed so I
was pretty sure that we were no longer on the volcanically active zone. The
structure we had visited was an ancient volcanic edifice that had been completely
dismantled by tectonic activity. The area appeared chaotic with tall, nearly vertical
cliffs. I named the area ‘‘Mount Jupiter’’.
Diving on the Mid-Atlantic Ridge in the FAMOUS Area
185