get acquainted with the submersible’s personnel and to learn about the constraints
of using the submersible’s equipment. However the most crucial questions were
concerned with how would the scientists react, and how would they work, while
being enclosed inside a sphere with a diameter of only 2.20 m, at more than
2000 m depth below the sea’s surface. Would the scientists be able to ignore the
huge water column above their heads? How would this situation influence their
work on the sea floor? The only way to know was to send these men to the bottom
of the sea, and see what happened.
I must say that at the beginning it was not easy for me. During my first dive, I
was somewhat uncomfortable and even a little scared about going down to the
ocean floor inside the submersible. I recall that during my first dive with Archimède, it was very difficult to focus my eyes and my attention on the seafloor. I had
a knot in my stomach and I was having trouble describing the geological features
outside the porthole. I even had a mental blackout for several tens of minutes.
Visit to the Afar Region in Ethiopia
There are only a few subaerial regions where spreading segments emerge on the
surface and these areas are found in the East African Rift and in Iceland. The East
African Rift extends from the middle of East Africa up to the Gulf of Aden where
it becomes a submarine-spreading center in the Red Sea. Thus the Afar region was
the first training ground chosen for us to visit, in order to familiarize the divers
with what it might be like when diving on the Mid-Atlantic Ridge. The region of
the Afar is situated at the junction of two propagating oceanic ridge systems of the
East African Rift, one entering the Gulf of Aden and the other one moving further
north and going directly into the Red sea. Recent volcanism is confined today to
the axial zone on three volcanic chains: the Erta’Ale, Alayta and Tat’Ali. The
Erta’Ale chain is about 80 km long and is composed of seven volcanic cones.
Among these volcanic cones, the Erta’Ale volcano, formed during the last 1
million years, is the most active. It contains two lava lakes inside its crater, which
have been active since 1960 (Barberi and Varet 1970a, b). This is a shield volcano
about 613 m high with a basal diameter of about 50 km. Thus, our main goal was
to visit the Erta’Ale. The molten lava lakes on this volcano had been visited each
year from 1967 to 1973 by volcanologists from the Italian Centro Nazionale di
Ricerche (CNR) and from the French Centre National de la Recherche Scientifique
(CNRS).
The summit of the Erta’Ale has an elliptical form 1.5 km long and 0.7 km
wide. Jean-Louis was familiar with this region because he had worked for several
years in the area to study the various eruptions along the chain. A large eruption
covering the two lava lakes had occurred in February 1973. It was just a couple of
months later, in the spring of 1973, that we went on our expedition and found
ourselves driving along rocky trails in Toyota trucks. Our first camp was in the
region of Ardou-Coba located at the northern tip of the East African Rift on the
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7 Oceanic Spreading Ridges and Sea Floor Creation
of using the submersible’s equipment. However the most crucial questions were
concerned with how would the scientists react, and how would they work, while
being enclosed inside a sphere with a diameter of only 2.20 m, at more than
2000 m depth below the sea’s surface. Would the scientists be able to ignore the
huge water column above their heads? How would this situation influence their
work on the sea floor? The only way to know was to send these men to the bottom
of the sea, and see what happened.
I must say that at the beginning it was not easy for me. During my first dive, I
was somewhat uncomfortable and even a little scared about going down to the
ocean floor inside the submersible. I recall that during my first dive with Archimède, it was very difficult to focus my eyes and my attention on the seafloor. I had
a knot in my stomach and I was having trouble describing the geological features
outside the porthole. I even had a mental blackout for several tens of minutes.
Visit to the Afar Region in Ethiopia
There are only a few subaerial regions where spreading segments emerge on the
surface and these areas are found in the East African Rift and in Iceland. The East
African Rift extends from the middle of East Africa up to the Gulf of Aden where
it becomes a submarine-spreading center in the Red Sea. Thus the Afar region was
the first training ground chosen for us to visit, in order to familiarize the divers
with what it might be like when diving on the Mid-Atlantic Ridge. The region of
the Afar is situated at the junction of two propagating oceanic ridge systems of the
East African Rift, one entering the Gulf of Aden and the other one moving further
north and going directly into the Red sea. Recent volcanism is confined today to
the axial zone on three volcanic chains: the Erta’Ale, Alayta and Tat’Ali. The
Erta’Ale chain is about 80 km long and is composed of seven volcanic cones.
Among these volcanic cones, the Erta’Ale volcano, formed during the last 1
million years, is the most active. It contains two lava lakes inside its crater, which
have been active since 1960 (Barberi and Varet 1970a, b). This is a shield volcano
about 613 m high with a basal diameter of about 50 km. Thus, our main goal was
to visit the Erta’Ale. The molten lava lakes on this volcano had been visited each
year from 1967 to 1973 by volcanologists from the Italian Centro Nazionale di
Ricerche (CNR) and from the French Centre National de la Recherche Scientifique
(CNRS).
The summit of the Erta’Ale has an elliptical form 1.5 km long and 0.7 km
wide. Jean-Louis was familiar with this region because he had worked for several
years in the area to study the various eruptions along the chain. A large eruption
covering the two lava lakes had occurred in February 1973. It was just a couple of
months later, in the spring of 1973, that we went on our expedition and found
ourselves driving along rocky trails in Toyota trucks. Our first camp was in the
region of Ardou-Coba located at the northern tip of the East African Rift on the
174
7 Oceanic Spreading Ridges and Sea Floor Creation