The 16th Nautile dive of the SMARTIES cruise, on August 8, 2019, was aimed at the investigation of the relationship between tectonics and volcanics at the southern tip of an axial volcanic ridge located between the Equator and 0°10’S. The bathymetry shows that the ridge is affected by several fault scarps.
3D view of the dive location on the axial volcanic ridge. © SMARTIES cruise 
Lava tubes and pillows. © SMARTIES cruise
During the dive, we have surveyed several fault scarps, and observed and sampled basaltic tubes and pillows. In some areas, we have observed a divergence of the tubes suggesting the location of eruptive centers. Some of the slopes on the tip of the volcanic ridge are very sedimented, and others show volcanic structures and fault scarps oriented N110 or N150°E.
Outcrops of volcanic tubes and pillows, some broken along the fault scarps. © SMARTIES cruise 
Debris of basaltic pillows in a large area of scree, also common during the dive. © SMARTIES cruise
The dive was 5.5 hours long at the bottom, and about 9 hours total. We started at a depth of 4227m, and left the seafloor from a depth of 3794m. An excellent series of observations and samples, with relatively fresh basaltic glass in several samples!
By A. Briais