The brief eruption of Kilauea earlier this week was three years in the making.
Kilauea began erupting about 12:30 a.m. Monday and had largely petered out by around 9 a.m., with all lava emissions ceasing shortly after noon — although the Hawaiian Volcano Observatory has not declared the eruption over, just paused.
But Ken Hon, scientist in charge at HVO, said the initial signs of the eruption were detected in August 2021.
The area the eruption occurred, about 2.5 miles southwest of Halema‘uma‘u crater, is less conducive for sustained eruptions than more prolific areas like the volcano’s summit or its East Rift Zone, Hon explained.
“The Southwest Rift Zone is kind of cuddled against Mauna Loa, and Mauna Loa exerts a lot of its own pressure on the system,” Hon said.
Consequently, Hon said, lava had taken years to intrude beneath the land southwest of the crater. August 2021 was the first sign of magma intrusion in the area, and sporadic seismic activity over the next several years indicated the magma’s slow progress toward Monday’s eruption.
“The eruption was interesting in that we detected movement so early on,” Hon said. The final indication before the eruption began was the upward movement of an underground lava dike, which HVO had picked up about six hours before lava breached the surface.
Monday’s eruption was longer, but less productive, than the previous one in the area, which took place in 1974. While that eruption lasted only about six hours, it generated about 10 million cubic meters of lava that covered roughly 2.75 square miles.
Monday’s eruption only covered about 350,000 square meters, with an estimated 100,000 to 400,000 cubic meters of material, Hon said.
Despite the brevity of the eruption, Hon said it still decreased the overall subterranean pressure at the summit — “but that pressure is still quite high,” he added.
Hon said Kilauea’s recent behavior seems to potentially indicate a new phase of volcanic activity, one characterized by a series of “pulses” of activity instead of sustained events over longer periods of time.
“It’s sort of like turning the faucet on high for a little bit and then turning it off again over and over instead of just leaving it on low for a long time,” Hon said. “That’s what the evidence seems to point to, anyway.”
While no lava has emerged from the area since Monday, there remains elevated activity, including a higher-than-typical rate of sulfur dioxide emissions (about 6,000 tons a day) and signs of volcanic tremor, which indicates the underground movement of magma. HVO continues to monitor the area for signs the eruption is resuming.
Parts of Hawaii Volcanoes National Park, including Hilina Pali Road, Kulanaokuaiki Campground, Pepeiao Cabin and Maunaiki Trail, remain closed to the public.
Email Michael Brestovansky at mbrestovansky@hawaiitribune-herald.com.