Puu Oo eruption over after 7 quiet months, scientists report

After seven months of no surface activity, the Puu Oo eruption on Kilauea Volcano’s middle East Rift Zone can be considered over, according to scientists at the U.S. Geological Survey’s Hawaiian Volcano Observatory.

Since first erupting Jan. 3, 1983, Puu Oo was continuously active over its 35-year history, except for more than 100 brief pauses lasting from a few hours to two months. The end came suddenly with a catastrophic collapse in April that left the vent and surrounding flow fields devoid of lava through the rest of 2018.

The HVO’s weekly “Volcano Watch” report issued Thursday said it is “extremely unlikely” lava activity would resume within Puu Oo, declaring a “concluding milestone for this long-lived event.”

The April collapse is believed to be connected to the subsequent eruption in Kilauea’s lower East Rift Zone that started May 3 in the Leilani Estates subdivision. Two dozens fissures opened in that event, producing lava flows that eventually covered 13.7 square miles while destroying 716 homes and displacing thousands of residents.

HVO scientists aren’t ready to declare the more recent eruption done yet, even though fissure 8, the most active of the vents, has quieted down and collapses at the Kilauea summit have subsided since August.

Puu Oo’s six longest hiatuses lasted from one to two months and occurred in between fountaining episodes in the first two years, according to the “Volcano Watch” report. In 1992, 1993, 1996 and 1997, there were eruption pauses of 10, eight, nine and 24 days, respectively.

As recently as 2011 there were pauses of 18 and six days.

Based on criteria from the Smithsonian Institution’s Global Volcanism Program, an eruption can be considered ended if there’s no eruptive activity over a 90-day period. However, based on its historical knowledge of rift zone eruptions, the HVO is a little more conservative, noting that pauses lasting more than 3-1/2 months have ended local eruptions.

The lack of activity at both Puu Oo and fissure 8 “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.”

The report 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 said. “When a new eruption does occur, ground cracking, gas emissions, seismicity and deformation can increase rapidly.”

HVO is maintaining 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.