Geology: Birth and evolution of two volcanic islands

The birth and evolution of two volcanic islands in the southern Red Sea are reported this week in Nature Communications. Satellite images show that the islands were formed in two short explosive eruptions in 2011 and 2013, and that they were strongly affected by wind and coastal erosion in the months and years following. The study also suggests that the region is more volcanically active than previously thought.

How new volcanic islands form is not well understood, particularly those along mid-ocean ridge systems (underwater ridges present where the seafloor is spreading), as witnessed events are exceptionally rare. Here, Wenbin Xu, Joel Ruch, and Sigurjon Jonsson used remote sensing techniques to show that the two new islands in the Zubair archipelago both grew rapidly during the initial eruptive phases, fed by two fractures filled by magma, called dykes. The authors modelled the ground deformation observed on the neighbouring islands in the archipelago and their findings suggest that the dykes are at least 10km in length, much longer than the size of the islands might indicate.

The study indicates that the Zubair archipelago may be a part of a previously-unrecognised volcanically active zone. This is corroborated by local earthquake swarms of the type that typically accompany magma intrusions. Similar seismic swarm sequences have been recorded during the past few decades but their significance went unnoticed; the authors suggest these also indicate a period of sustained magmatic activity in the area.