An international team of geophysicists examining the Southern Indian Ocean floor witnessed a section greater than two meters split apart, releasing millions of cubic meters of stored-up magma within just a few days.
Jean-Yves Royer, a marine geophysicist at the French National Centre for Scientific Research (CNRS) in Brest and a co-author of the study detailing the team’s serendipitous discovery, said witnessing the ocean floor splitting apart in real time was “a major surprise,” while the team hailed the scientific value of finally witnessing these processes up close.
Scientists Have Never Witnessed The Ocean Floor Splitting Apart in Real Time
Because the ocean floor is dynamic, the movement of tectonic plates pulling the existing crust away from mid-oceanic ridges allows magma to well up to the surface. When it dries, this material solidifies, adding to the existing crust. While scientists have understood this process for decades, no one has ever witnessed the phenomenon directly. This absence has left a gap in scientific knowledge that, as study co-author Isobel Yeo, a geoscientist at the National Oceanography Center in Southampton, UK, notes, persists to this day.
“We still know remarkably little about the frequency, magnitude, and dynamics of the eruptions and tectonic processes that build them”, the researcher explained
To try to fill that gap, the team focused its research on a section of the seafloor called the Southeast Indian Ridge, which runs east to west across the Indian Ocean. Due to its location, the ridge separates two tectonic plates, the Antarctic and the Australian.
The team notes that these two plates, which contain Antarctica and Oceania and the surrounding oceanic crust, are continuously moving in opposite directions by roughly six centimeters each year. Although both plates are exerting stress on the ridge, the team said the northward movement of the Australian plate accounts for most of this annual expansion.
The motion dynamics can also change by location. For example, one section of the Australian plate may stay stationary for a period and then suddenly experience a large surge in motion. These sudden events are accompanied by earthquakes.
Ocean Floor Movement in Real Time
In hopes of catching the ocean floor splitting in real time, Royer and colleagues ventured to the Southeastern Indian Ridge in February 2024. Once on site, the team deployed three categories of sensors at several different locations along a 100-kilometer stretch of the ridge. The sensor array included five hydrophones that detect underwater sound, including the telltale sonic waves produced by earthquakes. The team also deployed 15 battery-powered acoustic beacons designed to emit and detect sounds at selected locations along the ridge.
Because the acoustic beacons can produce and receive sounds, the team programmed them to exchange audio signals every four hours. This regular exchange allowed the team to measure the time between sound and response, which they used to determine the distance between the two beacons at four-hour intervals.
After the sensors were all in place, the team’s efforts finally paid off. According to the study, the carefully placed hydrophones began to detect seismic tremors on the ocean floor. These signals were followed by several days of acoustic beacon returns, indicating some of the stations had moved. When the team calculated the time between beacon signals, they determined that some sections of the ocean floor had moved by “at least” two meters as they were pulled away from the ridge.
The team also found evidence that the ocean floor was splitting apart in real time, altering the ocean floor’s depth. According to a reading from a single pressure sensor, the depth change caused by the event was “substantial.”
a rare direct view of these processes in action
In the study’s conclusion, the research team estimates that 160 million cubic meters of lava rose between the split ocean floor and spilled onto the seafloor. They also suggested that the magma explosion emptied a reservoir that had accumulated along the ridge, which caused portions of the floor to “subside.”
Royer said the team was only expecting to find a vertical displacement of “a few centimeters.” Instead, he notes, “we measured 4.2 meters.” The team said this large amount of change suggests that three to six decades’ worth of stress from the northward movement of the Australian tectonic plate was released during the ocean-floor-splitting event.
When discussing the significance of witnessing the ocean floor splitting apart in real time for the first time, Yeo said their study “provides a rare direct view of these processes in action.”
The study “Anatomy of a seafloor spreading event captured by in situ seismogeodesy” was published in Nature.
Christopher Plain is a Science Fiction and Fantasy novelist and Head Science Writer at The Debrief. Follow and connect with him on X, learn about his books at plainfiction.com, or email him directly at christopher@thedebrief.org.
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