Rifting Event at Southeast Indian Ridge Produced 160 Million Cubic Meters of Lava

A rifting event began on 26 April 2024 at the axis of the Southeast Indian Ridge near 37° S. The episode started as a rapidly migrating swarm of extensional seismicity along the axial valley and produced 4 m of subsidence of the valley floor together with more than a metre of horizontal extension across it.

@Nature reported that the event involved deflation of a sill-like reservoir that fed propagating dykes.

The dykes led to the outpouring of about 160 million m³ of lava at the seafloor in roughly 16 days. The same measurements showed both seismic and aseismic slip on valley-bounding normal faults and later triggered seismic activity on the adjacent transform faults. Instruments had been deployed across the ridge axis and the nearby Amsterdam transform fault two months earlier.

Data came from hydroacoustic recordings, direct-path ranging, bottom-pressure sensors and repeated seafloor mapping. @Nature reported that large-scale aseismic slip induced by magmatic processes may be the primary mechanism by which mid-ocean-ridge normal faults accumulate displacement.