July 26, 2007
A weekly feature provided by scientists at the Hawaiian Volcano Observatory.
Kilauea?s School of Magma and Motion trumps Hogwarts?
For the Harry Potter fans of the world, the stroke of midnight on July 21 was a momentous event. The final episode of J.K. Rowling?s tale centered on Hogwarts School of Witchcraft and Wizardry was released amidst much revelry and celebration. At the same time, Tutu Pele was creating some magic of her own on Kilauea.
As hard-core celebrants were getting ready for Harry Potter parties, a magma body was preparing to move east of Pu`u `O`o. For the past 16 years, Pu`u `O`o has been the main character in the current eruption, but for Father?s Day this year, Kilauea?s gift was a change in activity. Since that time, the east rift has been host to earthquake swarms, ground cracking, magma intrusions, new eruptive fissures and lava flows, an 11-day eruptive pause, and multiple collapses at Pu`u `O`o.
During the past week?s chapter, shortly before midnight of July 21, the Pu`u `O`o cone began to inflate sharply while the summit began to slowly deflate. Activity at Pu`u `O`o waned, and the floor of the crater sank. There was no unusual seismic tremor or earthquakes, but sometime after midnight, as die-hard Potter fans were digging into their new books, a new fissure eruption was in progress just downrift of Pu`u `O`o.
Residents of lower Puna observed a strong pre-dawn glow from the east rift zone, and HVO field crews, dispatched on the tail of tropical storm Cosme, confirmed that the eruption was well underway. A series of fissures was active ? the uppermost one, located a mere 120 meters (400 feet) east of the rim of the Pu`u `O`o crater, waned within a matter of hours. Lava was gently spattering from the lower fissures to heights of 5 meters (16 feet). Lava flows traveled to the northeast and approximately one kilometer (0.6 mile) to the southeast, reaching a point 4 km (2.5 mile) above Royal Gardens subdivision. The fissure system initially spanned a total distance of 1.7 km (1 mile). Individual fissures varied in length from 500-950 m (0.3?0.6 mile). The lower fissure system nearly reached the base of Kupaianaha, the active vent from 1986-1992, which produced the flows that covered Kalapana.
As of this writing (July 25), the newly erupted material covers an area of over 85 hectares (210 acres), with flow thicknesses ranging from 5-15 meters. During the height of activity, lava that pooled over the fissures created bubbling ponds perched high above scientists who mapped and measured close to the original ground level. Small spatter cones whistled audibly as they funneled escaping volcanic gas through narrow openings. Broad streams of lava were visible in the evenings on the newly installed web camera on Pu`u `O`o that looked across the active ponds and flows.
The current event is in the same area as a three-week eruption in 1991 that occurred when activity at the Kupaianaha vent was waning and the locus of activity was shifting back to Pu`u `O`o. Clearly the long-lived east rift eruption is in a period of transition, and monitoring the changing dynamics requires Constant Vigilance. At this time, it is unclear if Pu`u `O`o will reclaim its place as a leading character.
For Harry Potter and volcano fans alike, July 21, 2007, represented a special day. In contrast to Rowling?s concluding book, it is unlikely that Kilauea?s ?Harry Potter? event will mark the final chapter for the long-lived east rift eruption. It seems fitting, however, that the captivating activity of July 21 is accompanied by a celebration of magic. For a comprehensive and up-to-date description of the current activity see http://hvo.wr.usgs.gov.
Early last Saturday, July 21, after nearly three weeks of refilling, the floor of Pu`u `O`o subsided as lava erupted from new fissures on the east side of Pu`u `O`o cone. The fissures, extending along a line nearly a mile long, began to pour lava onto the ground between Pu`u `O`o and Kupaianaha. The upper portion of the fissure system stagnated by mid-morning on Saturday, but the lower fissures continued to erupt throughout the past week.
Though one lava flow reached just over half a mile from the fissures during the first day of activity, most of the lava has piled up fairly close to the vents. Four large lava ponds, perched up to about 50 feet above the surrounding lava surface, were constructed over the erupting fissures early in the week. Three of the ponds had broken through their walls by mid-week, sending lava gushing out as thick `a`a flows, before promptly beginning to form new ponds. By Thursday, the day of this writing, the level of activity from the fissures had noticeably declined. The level of the lava in the ponds had gone down, and the pond walls had become exposed. The number of lava overflows from the edges of the ponds had also subsequently decreased.
Vent areas are hazardous. Access to the eruption site, in the Pu`u Kahauale`a Natural Area Reserve, is closed, and questions may be directed to the Hilo Division of Forestry and Wildlife Office at (808) 974-4221 (a press release is available at http://www.state.hi.us/dlnr/chair/pio/HtmlNR/07-N076.htm).
In response to this eruption, the summit of Kilauea Volcano started to deflate just after midnight on July 21; thus far, the summit has deflated nearly 7 microradians ? small in comparison to the 50-microradian inflation on June 17 and 18 and the more-than-30-microradian inflation since. Seismic tremor levels remain low; the number of earthquakes beneath the upper east rift zone has declined this week, compared to the past several.
Two earthquakes beneath Hawai`i Island were reported felt within the past week. A magnitude-3.6 earthquake occurred at 10:15 p.m. H.s.t. on Sunday, July 22, and was located 8 km (5 miles) southeast of Ho`okena at a depth of 14 km (9 miles). A magnitude-3.2 earthquake occurred at 8:59 a.m. on Wednesday, July 25, and was located 1 km (1 mile) southeast of Pu`ulena Crater at a depth of 3 km (2 miles).
Mauna Loa is not erupting. No earthquakes were located beneath the summit. Extension between locations spanning the summit, indicating inflation, continues at steady, slow rates, which have slowed further since May 2007.
Updated: July 30, 2007 (pnf)