Signatures of widespread Surtseyan volcanism at the northern Reykjanes ridge

Submarine explosive volcanism shapes seafloor morphology, impacts marine ecosystems, and poses risks to maritime infrastructure and coastal communities. However, its occurrences and drivers remain poorly constrained, especially for basaltic systems. Here we present evidence for widespread phreatomagmatic volcanism at the Reykjanes Ridge north of ~63.2°N, derived from high-resolution seismic reflection profiles, multibeam bathymetry, and seafloor imagery. Our data indicate a first-order depth control on eruption style: effusive volcanism dominates below ~300 m, producing hummocky edifices with strong seismic attenuation, whereas shallower depths favour Surtseyan eruptions, forming smooth volcanic cones with flanks comprising stratified, outward-dipping seismic reflections. When eruptions occur close to the water–air interface, flat-topped volcanoes form, some emerging as ephemeral islands before being submerged by storm wave base erosion. Our results show that Surtseyan eruptions have been a dominant and recurrent process along the Reykjanes Ridge north of ~63.2°N since the Last Glacial Maximum.