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Volcanowatch

July 10, 2008

A weekly feature provided by scientists at the Hawaiian Volcano Observatory.


An exciting end to June at Kīlauea

A littoral explosion at dusk. Explosions such as this have been common throughout the last several weeks at the Waikupanaha entry.  June 29, 2008.
A littoral explosion at dusk. Explosions such as this have been common throughout the last several weeks at the Waikupanaha entry. June 29, 2008.
One of the most surprising aspects of the current summit eruption at Kīlauea Volcano, which started in March of this year, is that there has been almost no change in surface deformation trends. Past summit eruptions have been accompanied by rapid inflation prior to the start of an eruption, followed by equally rapid deflation. During the present period, however, the summit of Kīlauea has shown no change from the trend of gradual deflation since July 21, 2007, when the eruption site migrated about 2 km (1.5 miles) downrift from Pu`u `Ō`ō. No change, that is, until just a few weeks ago.

On June 24, tiltmeters at Kīlauea's summit and at Pu`u `Ō`ō began showing inflation-the first time sustained inflation has occurred at both sites since July 21, 2007.

In addition to the change in ground deformation, other types of monitoring data indicated a shift in the style of eruptive activity. Throughout early and mid-June, the intensity of the glow from the summit vent had decreased, relative to the strong glow seen in April and May. In late June, however, the summit vent began glowing brighter.

The intensity of the glow, in fact, correlates with bursts of seismic tremor that occur every few minutes, with more glow during the tremor bursts and less between bursts. These tremor bursts also increased in magnitude and frequency in late June. The correlation between tremor and glow led HVO scientists to infer that gas bubbles were bursting through a crusted lava surface beneath the Halema`uma`u vent. Increases in the strength of both the glow and tremor bursts may have indicated rising of the lava surface.

Another late June change in activity was the occurrence of surface lava flows from the east rift zone for the first time in several weeks. Lava broke out of the tube system, both on the east rift zone and above the Royal Gardens subdivision. At the same time, enough lava was being transported through the tube system to result in spectacular littoral explosions at the ocean entry during early July. All of these signs point to a lava tube system that was full to the point of overflowing.

Taken together, this evidence suggests that Kīlauea was engorged with magma, starting in late June. Increased magma in the caldera and east rift areas resulted in inflation of the summit and Pu`u `Ō`ō and, possibly, rising of the lava column in the Hamema`uma`u vent. Magma was also being delivered to the eruption site at a greater rate than normal, resulting in the numerous surface lava flows.

What might be the result of such activity? It is conceivable that more magma within Kīlauea's plumbing system could result in a change in the east rift zone eruption site, much like that which occurred in mid-2007. Lava might even erupt from the Hamema`uma`u vent, forming a lava lake at the summit.

Of course, Pele seems to enjoy keeping us on our toes. On July 1, deformation at Pu`u `Ō`ō stabilized, and the summit began to deflate, suggesting that even more magma was being fed from the summit to the east rift zone eruption site. Lava flow activity on the east rift zone and above Royal Gardens continued to increase. On July 7, a spectacular fountain formed near the TEB (Thanksgiving Eve Breakout) vent, possibly due to partial blocking of the lava tube system. At the summit, however, the intensity of glow from the Halema`uma`u vent has waned, suggesting that, at least for the moment, volcanic activity will focus on the east rift zone.

The weeks since June 24 have been a significant departure from "normal" trends of deformation during the current summit eruption, and also saw the most surface lava flow activity in several months. What caused Kīlauea to suddenly fill with magma and, just as suddenly, begin to drain?

One explanation is that the lava supply to Kīlauea fluctuates on timescales of days to weeks, causing rapid changes in surface deformation and eruptive activity. Although the causes of these fluctuations are not clear, the variations obviously are an important control on the activity we observe at the surface.

HVO will remain vigilant for future changes in the amount of magma coursing through Kīlauea's veins. Such activity should be easy to detect, given the excellent seismic, deformation, gas, and visual monitoring of the volcano, both at the summit and along the east rift zone. We invite you to follow along by checking HVO's Webcams, data plots, and daily activity updates available at http://hvo.wr.usgs.gov.

Activity update

Kīlauea Volcano continues to be active. A vent in Halema`uma`u Crater is erupting elevated amounts of sulfur dioxide gas and very small amounts of ash. Resulting high concentrations of sulfur dioxide in downwind air have closed the south part of Kīlauea caldera and produced occasional air quality alerts in more distant areas, such as Pahala and communities adjacent to Hawai`i Volcanoes National Park, during kona wind periods.

Pu`u `Ō`ō continues to produce sulfur dioxide at even higher rates than the vent in Halema`uma`u Crater. Trade winds tend to pool these emissions along the West Hawai`i coast. Kona winds blow these emissions into communities to the north, such as Mountain View, Volcano and Hilo. As of this writing (July 10), the gas vent below the east rim of Pu`u `Ō`ō was spattering weakly, with some spatter reaching the crater rim. At least two other vents within the Pu`u `Ō`ō crater were also spattering. The one near the western end of the crater was spattering vigorously and sporadically, feeding a small lava pond on the crater floor.

Lava continues to erupt from fissure D of the July 21, 2007, eruption and is supplying several breakouts along the 2007 Thanksgiving Eve Breakout (TEB) tube system above the pali and near the top of Royal Gardens. Activity was quite vigorous early in the week, feeding multiple breakouts, including a 10-15-m-high lava fountain. By July 10, activity had diminished, with only sparse surface flows observed.

Lava also continues to flow through what remains of Royal Gardens and across the coastal plain to the ocean in a well-established lava tube active now for several months. When the surface activity intensified upslope early in the week, the Waikupanaha ocean entry diminished significantly and appeared nearly inactive. Full vigor had returned by July 10, with small explosions and a large plume.

Be aware that lava deltas could collapse at any time, potentially generating large explosions. This may be especially true during times of rapidly changing lava supply conditions, as have been seen lately. Do not venture onto the lava deltas. Even the intervening beaches are susceptible to large waves generated during delta collapse; avoid these beaches. In addition, steam plumes rising from ocean entries are highly acidic and laced with glass particles. Check Civil Defense Web site (http://www.lavainfo.us) or call 961-8093 for viewing hours.

Mauna Loa is not erupting. Two earthquakes were located beneath the summit this past week. Continuing extension between locations spanning the summit indicates slow inflation of the volcano.

Four earthquakes beneath Hawai`i Island were reported felt within the past week; all occurred on Tuesday, July 8, 2008. A magnitude-2.7 earthquake occurred at 00:06 a.m., H.s.t., and was located 2 km (1 mile) southwest of Kīlauea summit at a depth of 1 km (1 mile). A magnitude-3.2 earthquake occurred at 00:38 a.m. and was located 3 km (2 miles) southwest of Kīlauea summit at a depth of 400 m (0.2 miles). A magnitude-2.8 earthquake occurred at 7:36 a.m. and was located 5 km (3 miles) northwest of Pa`auilo at a depth of 9 km (5 miles). A magnitude-1.8 earthquake occurred at 10:09 p.m. and was located 3 km (2 miles) southeast of Captain Cook at a depth of 8 km (5 miles).

Visit our Web site (http://hvo.wr.usgs.gov) for daily Kīlauea eruption updates, a summary of volcanic events over the past year, and nearly real-time Hawai`i earthquake information. Kīlauea daily update summaries are also available by phone at (808) 967-8862. Questions can be emailed to askHVO@usgs.gov. skip past bottom navigational bar


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Updated: July 14, 2008 (pnf)