Oceanography

Graviluck, Momareto, and the Mid-Atlantic Ridge

The Graviluck and Momareto missions have just drawn to a close. Their goal was to set up a fully operational laboratory for the observation and analysis of the sea floor on the Mid-Atlantic Ridge in the Azores area. Coordinated by Ifremer¹ and INSU,² they are part of the MoMar (Monitoring the Mid Atlantic Ridge) international program, which aims to understand every aspect of hydrothermal processes at the Mid-Atlantic Ridge, a submarine mountain range which runs down the middle of the Atlantic Ocean. This ridge is where the Eurasian and African tectonic plates slowly move away from the North and South American plates, giving rise to submarine volcanoes. The oceanic crust, which is 5 to 7 km thick, continuously forms along the axis of the mid-ocean ridges which make up the boundary between tectonic plates.

The objective of the Graviluck mission was to study the structure and dynamics of this crust. Onboard two ships, the researchers measured seafloor spreading by installing pressure sensors coupled with altimeters with satellite link-ups. With this data, they are hoping to improve their models and explain the activity of the area studied by MoMar.

The aim of the Momareto mission was to study deep-sea biodiversity, and initial observations have been extremely fruitful. The seagoing researchers were able to map the fauna around the Lucky Strike volcano (Altitude 1700 m). This was the first ever in-depth study of such an ecosystem, and researchers are now back on shore analyzing the gathered data. Among the samples collected, the researchers are especially interested in a species of giant mussel which can measure up to 20 cm in width. They have left an instrument-equipped observation module in the vicinity of volcano to observe the mussels' movements over a year. The next seafloor expedition is expected to take place in the summer of 2007.