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January 14--Hot time on the flow field that night
Surge of magma from Kilauea's summit downrift to Pu`u `O`o.
Residents in east Hawai`i communities were treated to a bright glow in the night sky recently, owing to lava-flow activity near Pu`u `O`o. For some, the lava appeared to be dangerously close; the deceptive aspects of night vision and the impressive backdrop of glow created an illusion that lava was "nearly in the back yard." What disrupted the routine goings on at Pu`u `O`o?
At 6:15 p.m. on January 14, numerous small earthquakes began beneath the summit of Kilauea. The earthquakes signaled the abrupt movement of magma within the upper crust of the volcano. Within minutes, tiltmeters recorded the onset of steady inflation at the summit. Over the next two hours, from 6:20 to 8:35 p.m., the summit inflated by roughly 8 microradians as recorded by tiltmeters at the Hawaiian Volcano Observatory. This inflation, though imperceptible without highly sensitive instruments, affected a broad area of the summit region. Thus it corresponded to a sizable slug of magma newly available to surge through the dike system of the east rift zone toward the eruption site. The volume of magma involved is still being determined by modeling of tilt data and GPS measurements.
Upon arrival at Pu`u `O`o, the volume of the surge overwhelmed the existing plumbing system. Consequently:
- The tube system, which normally is only partly full, became engorged. Lava oozed from nearly every open skylight along the tube's path from the vents to the sea.
- Lava issued from vents and skylights on the south side of Pu`u `O`o--chiefly the May 12 vent and the minishield.
- This south-side lava headed downslope to the ocean. Progressing as pahoehoe and `a`a, it reached the crest of Pulama pali at 10:00 p.m. and finally stagnated at the foot of the pali--7 km from the vent and only 3.7 km short of reaching the ocean. (See map at foot of this page.)
- Four or five breakouts occurred along the coastal plain, feeding small lava flows.
Part of seismogram from the 24-hour period begin 0729 January 14, 1998, and ending 0718 January 15, 1998. Record is from the North Pit seismograph, located adjacent to Halema`uma`u, Kilauea caldera, Hawai`i Volcanoes National Park. Time advances from left to right and from top to bottom; the record is clipped at right and left sides. Separation between each line is 15 minutes. The regularly spaced small jogs in each line show one-minute intervals.
Tilt record from summit tiltmeter at Uwekahuna vault. Tilt is recorded in microradians; one radian equals 57.3 degrees. (For those unfamiliar with tilt units, one microradian is roughly the tilt created by inserting a dime beneath the end of one-kilometer-long beam.) The tilt record shows the abrupt inflation of Kilauea's summit area soon after the seismic swarm began, followed by deflation as a slug of magma moved from the summit to the Pu`u `O`o vent area, and finally recovery of the summit area to its pre-surge level.
View north-northwest to south flank of Pu`u `O`o cinder-and-spatter cone. Extent of new flows from Jan. 14 surge shown outlined in white. Distance between 55 spatter cone and May 12 vent is 100 m. Photo p0711, taken Jan. 15, 1998
One of the larger breakouts of lava from tube system, middle reach of flowfield, roughly the 2080-ft elevation. View is north-northwest; dark skyline slope is shield at base of Pu`u `O`o. Trees in kipuka on right are roughly 20 m tall. Photo p0720, taken Jan. 15, 1998.
New lava flows (light-colored) on coastal plain. Color contrast results from silvery glass that characterizes the surface of new flows. Distance from the near-ground grassy area to ocean is 2.5 km. Photo p0729, taken Jan. 15, 1998.
In the aftermath
All lava-flow activity was confined to the existing flow field. Only a narrow strip of vegetation was damaged as the lengthy, seaward-directed lava flow brushed against kipuka of rainforest within the field. Neither houses nor lives were endangered.
In its wake, the surge of magma from the summit drained the lava supply system briefly. The Uwekahuna tiltmeter shows deflation in response. Glow diminished as the night progressed. By Thursday morning, the lava tube system had only sluggish flow, the dribbling remains of the surge that passed through on the previous evening. At the coast, the lava entries dwindled. By Thursday night, steam plumes from the entries at Waha`ula and Kamokuna had ceased.
This pause in supply of lava to the tube system lasted only a day. By Thursday evening, January 15, Kilauea's summit had reinflated to nearly its previous extent. By noon Friday, lava could be seen refilling the tube system from Pu`u `O`o down to the 2000-ft elevation (nearly to Pulama pali). By Saturday morning, January 17, lava was again entering the sea at the Waha`ula and east Kamokuna entries, which are the discharge points of the tube system. Kilauea's east rift zone seem to have returned to its steady-state regime.
If you're interestedTwo news releases were issued as part of this volcanic activity: 0600 hours and 0900 hours on January 15.
Eruption-viewing opportunities change constantly, so those readers planning a visit to the volcano should contact Hawai`i Volcanoes National Park for the most current eruption information (808-985-6000). Additional photographs and descriptions of east rift eruptive activity may be found on the University of Hawai`i's web site.
This map current as of January 15, 1998. It shows the main body of new lava emplaced on the evening of January 14. Numerous breakouts of lava from the tube system are still being mapped as this page was posted.
Eruption-viewing opportunities change constantly, refer to the HVO home page for current information. Those readers planning a visit to Kilauea or Mauna Loa volcanoes can get much useful information from Hawai`i Volcanoes National Park.
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