Sunday, January 27, 2019

Kīlauea's 2018 eruption--what happened, and how soon can it come again?


The 2018 Kīlauea eruption is less of a news story months after it stopped, but what the heck happened there, and can it happen again soon?

"The 2018 eruption of Kīlauea Volcano in Hawai‘i included both a summit caldera collapse and a flank fissure eruption, a complex event observed only a handful of times in modern history," wrote a team of more than 50 premier volcano experts in the January 25 issue of the journal Science.

And the short answer to the second question above is no, it probably can not happen again for many more years. More on that later.

Because Kīlauea is so well instrumented and staffed by geologists, the study of its eruption last year is providing details of how such eruptions work, and it will also provide important information on how to mitigate risk in future eruptions here and around the world, they said.

In March and April 2018, the summit and slopes of Kīlauea were inflating, indicating increasing underground pressure from magma buildup. There were changes at the summit and at the Pu`u `Ō`ō vent on the East Rift Zone.

On April 30, the Pu`u `Ō`ō crater collapsed, and scientists were tracking quakes as they began moving 20 kilometers downrift toward the residential area of Leilani Estates.

On May 3, the ground opened up there, and lava began erupting among house sites.

The island shook on May 4 with the biggest quake in 43 years—magnitude 6.9.

Over the next several months, the community was ravaged by absolutely immense quantities of lava—many times the amount that had been erupting daily from Pu`u `Ō`ō.

Fast-flowing rivers of molten rock ripped through homes, across roads, through gardens. Dense clouds of gas choked refugees and emergency workers, and acid burned the leaves of agricultural crops. Coastal parks and landmarks were destroyed. There were volcanic ash explosions at the summit. And much more.

Geologists determined that much of the lava came from magma stored in a chamber a mile or so deep, below the eastern side of Halema`uma`u Crater. It is one of two magma storage chambers under Kilauea, the other being deeper and off to the west.

We will number the four main things geologists figure were at play in how big and fast this went.

Both because (1) the pre-eruption pressure was so high, and because (2) the elevation of the Leilani Estates area vents was so low, geologists said, the volume of lava erupted was enormous—far more in a shorter time than ever before documented on this volcano.

The draining under the summit caused the ground above it to collapse, causing severe damage to roads and buildings at the summit. The famed Jaggar Museum was closed, and may never reopen due to structural concerns. The collapse of the summit (3) may also have created more underground pressure and shipped more magma to Leilani Estates.

That big May 4 earthquake (4) may also have opened up some space for the eruption to proceed at high volume.

Previous eruptions had gone on for years. Could this eruption, at these enormous levels of lava production, continue for very long? Even during the eruption, the experts were saying this could not continue forever, and sure enough, after just a few months, it ended.

"The strong hydraulic connection between the summit and (lower east rift zone), once established, remained until the summit magmatic system drained to a point at which the (lower east rift zone) eruption could no longer be sustained."

And could an eruption like this one come back anytime soon?

Probably not, the authors of the Science paper said.

"It may take several years before enough magma can accumulate beneath the summit to erupt," the Science paper said. As additional evidence, the authors noted that after a summit collapse in 1924, aside from some small eruptions at Halema`uma`u, there were no Kīlauea eruptions for 18 years.

The Hawaiian Volcano Observatory worked closely with county and state emergency management officials, and were able to provide robust and, importantly, early notification to the community about the eruption.

And this eruption provided so much data that it's likely future eruptions will be forecast even more accurately, the authors said.

The research collected during the 2018 eruption "yielded new insights into poorly known processes such as caldera collapse, small-scale explosive basaltic volcanism, vigorous lava effusion and degassing, and magma transport and flank stability at shield volcanoes," the science paper said.

"Continued exploitation of these rich datasets will undoubtedly yield additional discoveries that will refine understanding of Kīlauea Volcano and volcanic processes and hazards in general.

© Jan TenBruggencate 2019

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