Perched lava lake rising higher in Pu‘u ‘Ō‘ō crater

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Lava erupting steadily inside the crater of Pu‘u ‘Ō‘ō during the past three months is slowly approaching the lava high point of March 5, just before the crater floor suddenly dropped 115 m (380 ft) during the early hours of the four-day Kamoamoa fissure eruption.

Perched lava lake rising higher in Pu‘u ‘Ō‘ō crater...

Aerial view looking southwest into Pu‘u ‘Ō‘ō crater with its lava lake (shiny surface) perched 5-8 m above the surrounding lava flows. The lake and flows have filled in the crater vertically at least 100 m (328 ft) since the crater collapsed on March 5, and still have about 12 m (39 ft) to reach the previous high point and begin spilling into the pits on the western crater rim (in background). The perched lava lake and high emissions of sulfur dioxide gas make the Pu‘u ‘Ō‘ō area extremely hazardous. Ground access is restricted by Hawai‘i Volcanoes National Park and the Kahauale‘a Natural Area Reserve managers.

(Public domain.)

On June 29, the lava surface around the crater's edge was only about 12 m (39 ft) below the remnant of the pre-Kamoamoa eruption crater floor at the western end of Pu‘u ‘Ō‘ō crater, and 30 m (98 ft) below the eastern crater rim. The middle of the crater, however, was occupied by a lava lake "perched" 5–8 m (16–26 ft) above the surrounding crater floor.

Lava reappeared in the deepest part of the crater on March 26, three weeks after the crater floor collapsed at the onset of the Kamoamoa eruption. A persistent lava lake formed in the middle of the crater by mid-April, and overflows of the lake and flows from other short-lived vents on the western crater floor steadily filled the crater. For example, lava filled in the deepest part of the crater to a depth of about 73 m (240 ft) by May 6, 95 m (312 ft) by June 1, and 104 m (341 ft) by June 23.

All the while, the lake remained about the same size, about 200 m (656 ft) long and 100 m (328 ft) wide.

The lava lake surface typically rises and falls over periods of minutes to hours, and lava spilling from the lake has slowly built a levee around its perimeter. Each overflow adds to the levee, elevating the lava lake increasingly higher above the surrounding crater floor.

In addition to overflows, collapses of portions of the levee into the lake also lead to a sudden release of lava onto the crater floor. Such flows continue until the collapsed section of levee is constructed anew with lava—a repair that typically takes tens of minutes to a few hours. As lava pours from the lake, the lava lake's level drops, removing support for the levee and allowing other sections to collapse. This results in lava spilling from the lava lake at several different places at once.

The rise of the lava lake and infilling of the crater is setting the stage for interesting times ahead. In the coming weeks to months, it seems likely that lava will fill Pu‘u ‘Ō‘ō to overflowing, unless yet another collapse of the crater floor occurs as the supply of magma to Pu‘u ‘Ō‘ō's central vents is interrupted. Such interruptions could be caused, for example, by the opening of new vents on the flanks of Pu‘u ‘Ō‘ō, or by the opening of a new eruptive fissure, like the Kamoamoa fissure, uprift or downrift from Pu‘u ‘Ō‘ō.

The current activity is very similar to that occurring prior to the Kamoamoa eruption in March. The culmination of the present slow-filling of Pu‘u ‘Ō‘ō remains unwritten, but either scenario—collapse and a new outbreak or overflows—will be interesting. Visit the Pu‘u ‘Ō‘ō webcam to watch the unfolding activity (http://hvo.wr.usgs.gov/cams/POcam/).

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Volcano Activity Update

A small lava lake was present deep within the Halema‘uma‘u Overlook vent during the past week. Cycles of rise and fall were prevalent, causing the lava lake level—and the size of the gas plume—to fluctuate abruptly. Three small DI events occurred near the end of the week.

Lava also erupted continuously within Pu‘u ‘Ō‘ō over the past week, feeding a lava lake perched above the crater floor. Several breaches along the rim of the perched pond have allowed lava to spill out onto the crater floor. Due to these events, the crater floor has built up another 5 m (16 ft), making it 30 m (98 ft) below the east rim of the crater. Volcanic gas emissions from both vents remain elevated, resulting in relatively high concentrations of sulfur dioxide downwind.

No earthquakes beneath Hawai‘i Island were reported felt this past week.