Mid-Atlantic Ridge volcanism from deep-towed side-scan sonar images, 25 °–29 °N

We present deep-towed side-scan sonar mosaics of the inner valley floor of eight spreading segments at the slow-spreading Mid-Atlantic Ridge between 25 ° and 29 °N. An analysis of these images, which well-resolve features a few tens of meters in size, confirms that the multitude of small seamounts, with diameters between 0.5 and 3 km identified on the inner valley floor from previously collected multibeam bathymetry data, are volcanically constructed. Moreover, these images reveal that these volcanoes have distinct surface morphologies not evident in the coarser resolution multibeam bathymetry maps: 83% of the seamounts have a hummocky (bulbous) morphology; the other 17% have a smooth morphology. In addition to near-circular seamounts, small (1–2 km long) volcanic ridges are abundant in our study regions, and are not, in general, seen in the bathymetry maps. We combine these new morphological data with existing models for the construction of the shallow oceanic crust to obtain a better understanding of the melt delivery system that builds the distinctive seafloor topography at the slow-spreading Mid-Atlantic Ridge.