Scientists Observe Record Seafloor Expansion on Indian Ocean Ridge

Researchers have made the first direct observation of a seafloor expansion event at the southeast segment of the Indian Ocean mid‑ocean ridge, where the Australian and Antarctic plates diverge. An autonomous observatory installed two months before a sequence of earthquakes on 26 April 2024 recorded a displacement of 4.2 metres over six days, driven by the extrusion of magma from a roughly 2.5‑km‑wide reservoir that released more than 160 million cubic metres of lava. The seafloor moved at speeds up to five centimetres per minute before slowing to about 1.2 cm per day. The expansion measured more than one metre, while part of the ridge subsided by roughly four metres and the plates separated by over a metre.

The study, led by marine geophysicist Jean‑Yves Royer of the University of Brest, was published in the journal Nature. Royer noted, “We were very lucky to have all the instruments in place when this happened, and the large lava outflows occurred close enough that we captured the full data set.” The findings provide new quantitative detail on how new oceanic crust forms during tectonic spreading events.