After weeks of unleashing earthquakes and lava flows that have forced thousands of people to evacuate their homes, Hawaii’s Kilauea volcano has finally blown its top. Because Kilauea is one of the best-monitored volcanoes in the world, scientists hope that data on the event will help them to better predict when similar volcanoes are about to erupt. “We’ll be working on this set of data for our careers,” says Michael Poland, a geophysicist at the U.S. Geological Survey (USGS) Cascades Volcano Observatory in Vancouver, Wash.

The USGS says that the eruption began at 4:15 A.M. local time on May 17, when the volcano sent a plume of ash and steam more than 9,100 meters into the air.

The many instruments that had been placed on and around Kilauea were watching. The volcano bristles with equipment that continuously measures signs of geologic activity, such as ground movement, lava chemistry and seismic vibrations.

The first hint of an impending eruption came with a series of earthquakes on May 3. Soon after, fissures opened up in the ground as far as 40 kilometers away from the volcano’s rim—oozing lava that forced about 2,000 people to evacuate. The openings also depressurized the network of underground channels underneath Kilauea, including its lava chamber. As a result, the lava level within the volcano’s crater quickly dropped by more than 30 meters. It was, Poland says, “like someone pulled the plug in a bathtub.”

That caused the walls of the volcano to begin crumbling into the crater, creating a layer of rock atop the surface of the remaining lava. And once the surface of the still draining lava dropped below the water table, water began to seep into the crater, generating steam and pressure below the freshly formed rock cap.

History Repeats

Scientists at the USGS’s nearby Hawaiian Volcano Observatory suspected that a steam explosion was imminent: in 1924 the same pattern of oozing fissures around Kilauea had heralded a series of explosions.

The researchers were proved right when the pressure that built up in the crater sent debris and ash flying. But Poland says that steam explosions are hard to anticipate.

The hope this time, he adds, is that the extensive instrumentation on Kilauea and data collected from the latest eruption will allow scientists to develop better markers for predicting when a steam explosion is imminent.

Such events are “very small and localized, but if you’re in the neighborhood it’s going to cause an impact,” Poland says. In 2014 debris and ash from a steam explosion at Mount Ontake in Japan killed 63 people.

For now scientists in Hawaii and around the world are watching Kilauea and waiting to see what else the volcano will do. “This has so far been playing out how USGS said it would,” says Janine Krippner, a volcanologist at Concord University in Athens, W.V. “That itself is incredible.”

Kilauea probably isn’t done erupting yet, if the 1924 event is a guide: it went on for more than two weeks and caused more than 50 steam explosions. Hawaii’s state volcanologist, Bruce Houghton, says that the current event seems to be a type of complex eruption that occurs only once every 50 to 80 years.

Safety First

The recent activity has prompted the state of Hawaii to order the evacuation of several areas near Kilauea, protecting residents from the greatest eruption danger—flying rocks. But ash could still present a problem for people with respiratory problems, and officials are monitoring the wind and weather patterns to predict where the ash from the volcano will go.

Houghton says that it may be hard to know when it is safe for people to return to evacuated areas. In the 1960s an eruption at Kilauea stopped for a year and a half before the volcano suddenly resumed spewing ash. “It takes quite a long time to be certain things are completely over,” he says. “It will suit us just fine if it stops tomorrow, but the past record suggests it might go for months or years.”

Kilauea’s latest eruption “is an exciting event, but it’s coming at a cost,” Poland says, noting that dozens of homes have been destroyed and tourism is suffering. “We as the scientific community feel we owe it to the people being impacted to get it right and learn as much as we can,” he says.

Editors’ note: Since this article was published, Kilauea continued to erupt and trigger minor earthquakes until August 2, 2018, when things quieted down. As of this printing, the volcanic activity seems to have paused, although it is not necessarily over. About 700 homes on the Big Island were destroyed by flowing lava. No one was killed.