Volcano Watch: Perched lava lake rising higher in Pu‘u ‘O‘o crater

Aerial view looking southwest into Pu‘u ‘O‘o 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 ‘O‘o area extremely hazardous. Ground access is restricted by Hawai‘i Volcanoes National Park and the Kahauale‘a Natural Area Reserve managers.

Aerial view looking southwest into Pu‘u ‘O‘o 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 ‘O‘o area extremely hazardous. Ground access is restricted by Hawai‘i Volcanoes National Park and the Kahauale‘a Natural Area Reserve managers.

(Volcano Watch is a weekly article written by scientists at the U.S. Geological Survey’s Hawaiian Volcano Observatory.)

View looking east into Pu‘u ‘O‘o, its crater partly filled by lava flows accumulating on the crater floor. The active lava lake in the crater is 205 m (673 ft) long and varies in width from 80-115 m (262-377 ft). The West Gap pit is in the central foreground, and the Puka Nui and MLK pits are to the right (the MLK pit is in back). The crater has filled in vertically about 100 m (328 ft) since the crater collapsed on March 5, 2011, at the start of the uprift Kamoamoa eruption. It still has about 12 m (39 ft) to go to reach the level of the crater floor prior to the collapse. Photo courtesy of USGS/HVO

View looking east into Pu‘u ‘O‘o, its crater partly filled by lava flows accumulating on the crater floor. The active lava lake in the crater is 205 m (673 ft) long and varies in width from 80-115 m (262-377 ft). The West Gap pit is in the central foreground, and the Puka Nui and MLK pits are to the right (the MLK pit is in back). The crater has filled in vertically about 100 m (328 ft) since the crater collapsed on March 5, 2011, at the start of the uprift Kamoamoa eruption. It still has about 12 m (39 ft) to go to reach the level of the crater floor prior to the collapse. Photo courtesy of USGS/HVO

Lava erupting steadily inside the crater of Pu‘u ‘O‘o 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.

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 ‘O‘o 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.

The lava lake'€™s levee stands up to 8 m (26 ft) above the surrounding crater floor. This steep-sided levee impounds the lava and forms what is called a '€œperched'€ lava lake. Pieces of the rim occasionally collapse into the lake, leading to sudden and fast-moving overflows of lava onto the crater floor. Photo courtesy of USGS/HVO

The lava lake'€™s levee stands up to 8 m (26 ft) above the surrounding crater floor. This steep-sided levee impounds the lava and forms what is called a '€œperched'€ lava lake. Pieces of the rim occasionally collapse into the lake, leading to sudden and fast-moving overflows of lava onto the crater floor. Photo courtesy of USGS/HVO

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 ‘O‘o to overflowing, unless yet another collapse of the crater floor occurs as the supply of magma to Pu‘u ‘O‘o central vents is interrupted. Such interruptions could be caused, for example, by the opening of new vents on the flanks of Pu‘u ‘O‘o, or by the opening of a new eruptive fissure, like the Kamoamoa fissure, uprift or downrift from Pu‘u ‘O‘o.

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 ‘O‘o remains unwritten, but either scenario—collapse and a new outbreak or overflows—will be interesting. Visit the Pu‘u ‘O‘o webcam to watch the unfolding activity (volcanoes.usgs.gov/hvo/cams/PO…).

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