On April 30, the Pu’u O’o crater on Hawaii’s Kilauea volcano suddenly collapsed. It was the starting point for the volcano’s monthslong eruption, which went on to produce 320,000 Olympic-sized swimming pools’ worth of lava that transformed the landscape and ultimately destroyed 700 homes.

Now the U.S. Geological Survey’s Hawaiian Volcano Observatory and other scientists have published the first detailed summary of this paroxysm. The landmark study, published in the journal Science on Tuesday, unspools a timeline of this volcano’s most destructive eruption in recorded history and shows that it contained a combination of volcanic events that has seldom been observed.

Thanks to an unparalleled monitoring effort, volcanologists have gained a deeper understanding of America’s most hazardous volcano, which may help reveal the secrets of similar volcanoes around the world. What follows is a summary of key volcanic events in Kilauea’s 2018 outburst, in the order in which they occurred.

MAY

Kilauea is one of several active volcanoes on the island of Hawaii, the archipelago’s largest. Found in the island’s southeast corner, it has been erupting continuously since 1983. But by May of this year, a new eruption sequence had commenced, with two focal points: a flank area known as the lower east rift zone, a point where the volcano’s surface is gradually splitting apart, and the Halema’uma’u crater to the west at Kilauea’s summit.

Christina Neal, the scientist-in-charge at the Hawaiian Volcano Observatory and the study’s lead author, said this confluence of big volcanic events that went on for months meant that this eruption was “truly unprecedented in the modern record.” In fact, this was the largest such eruption from this rift zone in the last 200 years.

The collapse in April of the Pu’u O’o crater, located in the east rift zone, may have coincided with the breakdown of a subterranean barrier. That could have allowed magma at the site to flow through an established pathway toward the lower east rift zone.

On May 2, the Halema’uma’u summit crater’s lava lake — a persistent pool of bubbling lava inside the crater — began to drain and cracks appeared in the rift zone. The next day, the first fissure of many appeared in the Leilani Estates Subdivision and lava began to flow, prompting the evacuation of thousands of residents.

Increased seismic activity at the summit coincided with a magnitude 6.9 temblor beneath the volcano’s southern flank on May 4, the largest on the island in over four decades. The shaking likely resulted from a migration of magma pushing against the southern section of the volcano, which caused a fault to slip. Aftershocks continue to be felt more than seven months later.

By May 10, the lava lake within Halema’uma’u had dropped to around 1,070 feet below the crater floor as the magma below continuously migrated to the rift zone. As the underlying magmatic foundations of the summit disappeared, the entire crater floor began to subside in what would amount to 62 separate collapse events.

Major summit explosions were recorded May 15 and 17. The largest since 1924, they produced plumes 12,000 and 30,000 feet high. This activity was once thought to be driven by groundwater angrily reacting with draining magma. But Neal said that new data suggests that escaping magmatic gas drove the explosions.

JUNE-JULY

By the beginning of June, 24 fissures had appeared in the rift zone, with rivers of lava flowing — some all the way to the ocean — as fast as 3,530 cubic feet per second. More than 55,000 tons of sulfur dioxide emissions were emerging each day.

With old, stagnant magma already erupted, deeper magma had emerged. Fluid, packed with dissolved gases and erupting at 2,200 degrees Fahrenheit, it led to spectacularly high fountains of lava emerging from some fissures, topping out at 262 feet.

On June 2, the largest freshwater lake on the island vaporized in only 90 minutes. A lava delta also formed at Kapoho Bay over the next two months. One fissure, No. 8, gradually became the dominant fissure of the eruption, building a spatter cone 180 feet high. Kilauea’s summit, featuring near-daily collapse events, continued to periodically deflate.

By July, several secondary phenomena linked to the lava had been observed. Hot updrafts produced by the lava contributed to pyrocumulus clouds and fire whirls. Buried vegetation also began to thermally decompose near flowing lava, releasing methane that burst into eerie blue flames.

Sulfur dioxide emissions regularly mixed with water vapor to produce a suffocating vog. The violent quenching of lava as it met the Pacific Ocean produced laze, a mixture of hydrochloric acid, glass particles and steam.

AUGUST-SEPTEMBER

On Aug. 4, all volcanic activity abruptly declined. Seismic activity at the summit quieted and the rift zone experienced a dramatically reduced flow of lava until the last embers were extinguished. Sulfur dioxide emissions had nose-dived.

By the time the Hawaii Volcanoes National Park reopened Sept. 22, Kilauea’s lava covered 13.7 square miles of the island and there had been 1,640 feet of vertical collapse at the summit.

Scientists calculated that the collapsed volume lost from the summit roughly matched that of the amount of lava produced. Kyle Anderson, a geophysicist at the U.S. Geological Survey’s Volcano Science Center and co-author of the study, explained that with each collapse event came a surge of lava production at the rift zone.

Anderson said at a news conference Tuesday that this meant the summit and lower east rift zone were clearly interlinked in a devilish dance.

ERUPTION’S END

The Smithsonian Institution’s Global Volcanism Program defines an eruption as being over if the volcano has not experienced any volcanic activity across three consecutive months. Kilauea’s epilogue arrived Dec. 6, when the USGS declared that it was “very unlikely” the 2018 eruption at the rift zone would resume.

Magma still exists beneath the summit and rift zone. This means that a future eruption of some kind somewhere on Kilauea is a certainty. Whenever that occurs, scientists and disaster managers will rely on the insights gained from their close study of how the 2018 eruption unfolded to guide their response.

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