The holiday season is once more upon us, with the solstice arriving at 2:04 a.m. Hawaiian Standard Time on Sunday, December 21, and Chanukah, Christmas, and Kwanza following soon afterward. Many cultures and traditions mark the season with celebrations that include good food, cheer, and especially, light, to help dispel the darkness of winter.
Kilauea also appears to be observing the seasonal holidays. At the beginning of December, it seemed that the summit vent might be getting into the swing of things by producing the photogenic red glow that was ubiquitous through much of the summer and early fall. For locals and visitors alike, an evening watching the mesmerizing show from the rim of the caldera was cause for celebration. But, since mid-October, the glow has been notably absent.
The promise of extra volcanic glow for the solstice abruptly ended on December 4, when the familiar white, fluffy plume went through several brief ash-rich phases and then changed into a wispy, translucent shadow of its former self. The vent temperature also went down an extra step from the reduced values observed throughout the fall; then on December 5, the promising glow disappeared
The activity at Kilaueaâ€™s summit continued to exhibit both subtle and obvious changes â€“ perfectly timed with the Dutch observance of Sinterklaas, the celebration of the birthday of Saint Nicholas.
The dark, early morning hours of December 5 were heralded by loud booms, the sound of falling rock, and a thick, dirty plume which generated a notable dusting of ash. A flurry of small quakes occurred in the vicinity of Halema`uma`u, accompanied by very low frequency sounds and minor collapses of the vent rim. By December 6, a large slice of the vent rim had fallen in, and the vent diameter had increased to 98 meters (107 yards) â€“wide enough to house a football field.
Since that time, the summit activity has been characterized by small, and even smaller, ash and tephra falls. Much of it has likely been fragments crumbling from the older rock in the conduit wall and carried up in the escaping gas column, with only a very small amount of fresh, glassy spatter erupted. There may have been a tiny bit of glow observed, but it was subtle, at best. Vent sounds have been variable, ranging from solemn quiet to vigorous gas-jetting and tinkling rock-fall sounds.
Perhaps the most notable change that the casual Kilauea admirer would perceive is the wispy, languid plume that curls lazily from the vent. Indeed, the rate of SO2 gas release from the summit vent has dropped to about 20 percent of its maximum value since the vent opened in March, and about 40 percent of its average value for that time period. The reduction in summit SO2 emission rate may give the communities and farmers to the south and west in the Ka`u and Kona districts a welcome reprieve. Air-quality monitoring revealed that, since the onset of the summit eruption, the primary health standards for SO2 gas have been exceeded on 36 occasions in Pahala. Health standards for particle pollution have been exceeded 14 times in Pahala and 10 times in Kona. Prior to the onset of the summit activity, no exceedance of the health standards was recorded for either community.
Over the past week, residents in East Hawai`i would have been hard pressed to notice that summit SO2 emissions were a fraction of their typical amount. Kona wind conditions intermittently fumigated the communities adjacent to the National Park and along Highway 11 with substantial amounts of SO2 gas and acid particles, mainly from Pu`u `O`o but with some contribution from the summit. While summit emissions have declined markedly, the copious emissions from Pu`u `O`o continue. Currently they are about five times those at the summit. Although no health standards were exceeded at any of the East Hawai`i air quality monitoring stations in the past week, concentrations in the National Park exceeded 1 ppm, resulting in an â€œunhealthyâ€ condition advisory.
Kilauea may be observing the holiday season with a stutter in the summit activity, but historically, long-lived summit eruptions typically waxed and waned. Even with a growing volcanology toolkit, it is difficult to know exactly what will follow this most recent shift in activity. Perhaps things will have changed again by the time Santa arrives â€” or even by the time you read this.
Kilauea 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 Kilauea 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. There have been several small ash-emission events from the vent, lasting only minutes, in the last week. In addition, a series of three deflation-inflation cycles was recorded at Kilauea’s summit in the past week. These cycles normally cause short-term fluctuations in lava supply to the flow field.
Pu`u `O`o 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, while kona winds blow these emissions into communities to the north, such as Mountain View, Volcano, and Hilo. Lava erupting from the Thanksgiving Eve Breakout (TEB) vent at the eastern base of Pu`u `O`o continues to flow to the ocean at Waikupanaha through a well-established lava tube. Beakouts from the lava tube were active in the Royal Gardens subdivision and on the coastal plain in the past week. The flows on the coastal plain had reached 140 yards across the National Park boundary by last weekend but were stagnant when mapped on December 16. These flows have diminished over the past week, but may still be active near the base of the pali.
Be aware that active lava deltas can collapse at any time, potentially generating large explosions. This may be especially true during times of rapidly changing lava supply conditions. The Waikupanaha delta has collapsed many times over the last several months, with three of the collapses resulting in rock blasts that tossed television-sized rocks up onto the sea-cliff and threw fist-sized rocks more than 200 yards inland. Do not approach the ocean entry or 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. Call Hawai`i County Civil Defense at 961-8093 for viewing hours.
Mauna Loa is not erupting. One earthquake was located beneath the summit this past week. Continuing extension between locations spanning the summit indicates slow inflation of the volcano, combined with slow eastward slippage of its east flank.
Two earthquakes beneath Hawai`i Island were reported felt within the past week. Both were located at a depth of 2 km (1 mile).beneath the Steaming Bluffs – Sulfur Bank area on the north rim of Kilauea caldera. A magnitude-3.1 earthquake occurred at 4:05 p.m., H.s.t., on Monday, December 15, 2008, and a magnitude-2.6 earthquake occurred at 4:53 p.m. on Wednesday, December 17.
Visit our Web site for daily Kilauea eruption updates, a summary of volcanic events over the past year, and nearly real-time Hawai`i earthquake information. Kilauea daily update summaries are also available by phone at (808) 967-8862. Questions can be emailed to askHVO@usgs.gov.
This article was written by scientists at the U.S. Geological Surveyâ€™s Hawaiian Volcano Observatory.