Journal of Conference Abstracts

Volume 1 Number 2


FARA-InterRidge Symposium on the Mid-Atlantic Ridge

Reykjavik, June 1996

Extended Abstracts



The Preface to the volume is reproduced below. Abstracts are in alphabetical order of the surname of the first author. The suffix of their web address is XXX.html, where XXX is the page number within the volume. The page numbers of abstracts by any author can be found from the Index of Authors. Abstracts on any given topic may be found from the Lists of Symposia . Alternatively, abstracts can be found from the search facilities provided by Digital's Altavista service.



Preface

The Mid-Oceanic Ridge in the North Atlantic has been subject to particularly intensive study over the past several years, with many nations bringing research efforts to bear in this region, including France, the United States, the United Kingdom, Russia, Japan and Portugal.

The idea of a bilateral French-American program was introduced at the 10th joint
session of the United States-France Cooperative Program in Oceanography in December 1986. Task groups from the two nations met in May 1989 to finalize the framework for a
collaborative effort. General agreement was reached that the area of investigation should be the full length of ridge crest between about 40°N, near the Azores triple junction, and about 15°N, thus effectively encompassing the whole of the North America-Africa plate boundary. A Project Plan, setting out the scientific aims, design and organization of the programme was developed and the project, named the FARA (French-American-Ridge-Atlantic) Project, was initiated.

Although the Project Plan laid out overall objectives, the work was to be driven by
the impetus of individual investigators who would submit proposals through the normal peer review process of each nation. The first proposals were submitted in 1990 and the first field programmes took place in 1991. Initiallyconceived as a three-year programme, the
considerable demand for ship-time and constraints of fleet logistics led to its extension,
with the scheduling of some final cruises as late as 1996. At the conclusion of the sea-going operations, more than 20 expeditions using ships and submersibles of the United States and France will have been successfully completed.

The main emphasis of the FARA project was on the ridge axis itself: to document the range in, and understand the causes of, the variability of its properties for a similar average spreading rate. The principal secondary aim was to discover new sites of hydrothermal activity and to study their geology and biology. At the time the project started, little more than a quarter of the axial area of the ridge had been fully mapped using multibeam echo-sounders and there had been nearly no fine-scale sampling of multiple, sequential ridge
segments. Only two hydrothermal sites had been identified and practically nothing was known about how their character and location may be related to magmatic and tectonic
context.

During the duration of the FARA project, efforts spearheaded by other nations also became focused along the same portion of the mid-Atlantic Ridge. Russian operations
continued, the BRIDGE program of the United Kingdom directed a multi-expedition study to the stretch of ridge between latitudes 23°N and 30°N, and the European Community
coordinated a sea-going effort along the ridge crest near the Azores. In addition, the Ocean Drilling Program completed a two month leg at the TAG hydrothermal mound near 26°N in late 1995, which was preceded and followed by a series of associated experiments involving surface ships and submersibles.

The result of this work is an important transformation of our understanding of the
Mid-Atlantic Ridge. There is now virtually complete multibeam bathymetric coverage of
the ridge axis in the 15°N-40°N region, with some maps extending out to the equivalent of many millions of years off-axis. Taken together the new information on ridge morphology, tectonics and geophysics and the analytical results coming from several hundred new
sampling stations provide a powerful set of data for testing, developing and integrating
models of crustal creation and ridge segmentation. The number of known hydrothermal fields has been more than quadrupled and these include sites associated with hot spot
influence and sites associated with peridotites. There has been significant expansion of knowledge about the corresponding biological populations. Hypotheses for the volcanic and tectonic controls on hydrothermal activity are being substantially revised as more sites are identified in diverse geodynamic settings.

A significant part of the recent research is summarized in the abstracts presented
in this volume. Further progress in understanding ridge-crest and associated mantle processes along the Mid-Atlantic Ridge will need to include future investment in innovative and conceptually and technically difficult on-axis experiments. Off-axis investigations
will also be required in order to address questions of stability and change through time and better to assess the importance of fluxes of mass and energy away from the confines of the plate boundary.

The FARA project was conceived at the same time and grew during the same period as the InterRidge initiative, and has involved many of the same scientists. The fully international efforts that have taken place in the North Atlantic far exceed what would have been possible under the bilateral FARA program alone and the results demonstrate the potential of, and the need for, focused international actions. That this symposium is being held
under the auspices of InterRidge is therefore fitting and serves as a reminder that the
comprehension of ridge dynamics is ultimately a global issue appealing to the contributions of many nations as well as of all relevant disciplines.

The work reported here flows, of course, from the interest of the scientific community. It was made possible by the strong support of the various national institutions concerned,
in particular IFREMER and INSU in France, the NSF and NOAA in the United States,
and NERC in the United Kingdom. The associated symposium reflects their continued encouragement.

The meeting is also sponsored by Lamont Doherty Earth Observatory as a Ewing Symposium. Its organization was co-ordinated by the InterRidgeOffice in liason with the convenors, the symposium's scientific committee, the Iceland Tourist Bureau and Karl Gronvold of the Nordic Volcanological Institute. The abstracts were edited by Heather Sloan and Ruth Williams of the InterRidge Office.

H.D. Needham
(IFREMER)

C.H. Langmuir
(Lamont-Doherty Earth Observatory)