Minerals Report - International Seabed Authority

coordination to actually get to go to them and to do the preliminary
investigation.
In this regard, Dr German described international collaboration that
has been planned in the Artic basin this year and next year. Based on a
combination of French and American research programmes scheduled for the
summers of 2000 and 2001, Dr German said that a preliminary evaluation a
stretch of mid-ocean ridge from the Bouvet Triple Junction in the South
Atlantic to the Rodrigues Triple Junction in the Central Indian Ocean basin
will completed by Spring 2001. In parallel, he also said, an expedition by
Japanese, Russian, American, British and other European researchers to the
Knipovich Ridge that is north of Iceland and immediately south of
Spitsbergen will be undertaken to search for hydrothermal activity. Finally, in
the fall of 2001, an even more ambitious two-icebreaker expedition is
proposed, using the new US icebreaker “Healy” and the German R/V
“Polarstern” to investigate the presence and abundance of hydrothermal
venting along the Gakkel Ridge.
Dr. German turned his attention to the properties of plumes that can
assist prospectors in their search for hydrothermal activity and ultimately
massive sulphides deposits. He recalled that high temperature hydrothermal
plumes or high temperature hydrothermal vents produce hot fluids that rise
out of chimneys that percolate up from the sea floor. With regard to the
available technology for viewing this phenomenon, Dr. German pointed out
that from a submersible, in general one can probably only see about 10 metres
in any direction at best. In this regard, he informed participants that one of the
properties of plumes that have been utilized to obtain a visualization of them
from a greater distance in a submersible is their acoustic property. Dr.
German said that the plume rises because the water that initially comes out of
the vent is so hot that it actually has different acoustic characteristics from
ordinary deep ocean water. He informed participants that Professor Rona
and his colleagues had developed a technique to develop an acoustic image of
the plume from these characteristics, allowing the plume to be detected from
hundreds of metres away.
In relation to the rising plume, Dr. German pointed out that the plume
does not rise forever and that at a point in its ascent, it loses it's buoyancy and
INTERNATIONAL SEABED AUTHORITY 416