January 14--Hot time on the flow field that night
[Previous eruption updates may be accessed through our archive index.]
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:
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 two days following January 14
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.
This page was created on January 17, 1998, as a full update. The version shown here has been abbreviated for reposting on February 4, 1998, as a reference document.