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Puu Oo eruption considered over after seven months of no lava activity, USGS reports

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Puu Oo as viewed from a helicopter overflight on May 3. After a seven-month lapse in activity, USGS said it was “extremely unlikely” lava would resume activity within Puu Oo, and declared it a “concluding milestone for this long-lived event.”

Is the Puu Oo eruption on Hawaii island over?

The U.S. Geological Survey on Tuesday noted in its “Volcano Watch” update that seven months have passed with no surface activity at Puu Oo. The second to last day of December — Dec. 30 — marked the seven-month anniversary of no surface activity at Puu Oo, which began erupting on Jan. 3, 1983 at the middle East Rift Zone.

This, according to the USGS Hawaiian Volcano Observatory, along with no signs of imminent unrest, leads to the conclusion that “the Puu Oo eruption could be considered over.” After the seven-month lapse in activity, USGS said it was “extremely unlikely” lava would resume activity within Puu Oo, and declared it a “concluding milestone for this long-lived event.”

In its 35-year history, Puu Oo, erupted almost continuously, with more than 100 minor pauses of a few hours to a few days up until a catastrophic collapse in April left the site and surrounding lava flow fields devoid of lava through the rest of 2018.

The six longest pauses lasted one to two months long each, according to the USGS, in between fountaining episodes in the first two years.

In 1992, there was a 10-day pause after the Kupaianaha vent shut down, followed a year later with an eight day pause in 1993 after an uprift intrusion cause the Puu Oo crater floor to collapse. In 1996, a nine-day pause occurred after an observed surge in effusion rate.

The longest eruption hiatus after the fountaining phase lasted 24 days in February 1997 following the episode 54 fissure in Napau Crater. As recently as 2011, there were two pauses — an 18-day-long pause after the March Kamoamoa fissure, and a six-day-long pause after the episode 60 west flank breakout in August.

Is the eruption which began May 3 at the lower East Rift Zone over?

No similar declaration has yet been made, and seven months of no activity has not yet been reached. Since about August 2018, activity from fissure 8 has quieted down, and summit collapses at Kilauea summit have also subsided.

The latest report says Kilauea Volcano is not erupting, and that low rates of seismicity across the volcano, deformation, and gas release have not changed significantly over the past week. Sulfur dioxide emission rates from the summit and Puu Oo also remain low.

Based on criteria from the Smithsonian Institution’s Global Volcanism Program, no eruptive activity over a 90-day period can be considered the end of an eruption. Based on historical knowledge of rift zone eruptions, USGS said pauses lasting more than 3.5 months have ended their respective eruption.

The USGS, however, has kept Kilauea’s alert level at yellow, which means the volcano is exhibiting signs of elevated unrest above its known background level, or that volcanic activity has decreased significantly but continues to be closely monitored for possible renewed increase.

“This does not mean Kilauea Volcano is dead,” said the Volcano Watch report. “New eruptions have previously begun elsewhere on Kilauea after months to decades of quiet.”

USGS noted that magma is still being supplied to the volcano, with deformation data showing evidence of the movement of molten rock through the system, refilling the middle East Rift Zone.

“It’s important to note that Kilauea is still an active volcano that will erupt in the future, and associated hazards have not changed,” the report continued. “When a new eruption does occur, ground cracking, gas emissions, seismicity, and deformation can increase rapidly.”

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