(Volcano Watch is a weekly article written by scientists at the U.S. Geological Survey’s Hawaiian Volcano Observatory.)
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.
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.www.hawaii247.com