For the past decade, a suite of devices have been monitoring Axial’s every action — rumbling, shaking, swelling, tilting — and delivering real-time data via a seafloor cable. It’s “the most well-instrumented submarine volcano on the planet,” says Mark Zumberge, a geophysicist at Scripps Institution of Oceanography in La Jolla, Calif., who was not involved in the work.

But in November, a particular milestone caught Chadwick’s eye: Axial’s surface had ballooned to nearly the same height as it had before its last eruption in 2015 — fortuitously, just months after monitoring began. Ballooning is a sign that magma has accumulated underground and is building pressure.

The 2015 swelling allowed Chadwick, of Oregon State University’s Hatfield Marine Science Center in Newport, and colleagues to predict that year’s eruption — “our best forecasting success,” he says. The recent swelling, along with increased seismic activity that indicates moving magma, has led the researchers to narrow in on the next one.

The broader team of Axial researchers also has a new tool for estimating the day-of magma burst that will set things off. And other researchers recently used artificial intelligence to dig into recordings of earthquakes that preceded the 2015 eruption and identified exactly what patterns they should see hours ahead of the next one . “Will this precursory earthquake detection work?” Chadwick asks.