bob@uhmanoa.ics.hawaii.edu (Bob Cunningham) (04/27/88)
"Pau hana time" is s popular local phrase. Pau means stop, hana means work. Pau hana time is when you quit work. Although there are lots of uncertainties in predicting what a volcano will do, it is beginning to look like the five-year-old eruption of Kilauea volcano may be coming to an end, based upon some significant changes in the last couple of days. To recap: the current eruption began 3 Jan 1983. The initial phase was near Napau Crater inside the Hawaii Volcanoes National Park, but within a few hours had moved on to a site on Campbell Estate land where it eventually built a cinder cone later named Pu'u 'O'o (literally: the hill of O and O, a play on the first letters of the names of a couple of scientists at the USGS Hawaii Volcano Observatory). Early stages over the first year or so featured some very spectacular lava fountains ranging from 300 to 1,000 feet high. On 18 July, after 47 phases of periodic high fountaining, the eruption site moved further down the rift zone on the flank of Kilauea to what was later named the Kupaianaha lava pond and began a steady outpouring of 4.9 cubic meters per second (about 500,000 cubic meters per day...enough to since then have paved a multi-lane highway 1 foot thick from here to the Moon). Lava, first on the surface, then through a series of lava tubes, flowed down the mountain to the sea, creating some spectacular results there, including some extensive black sand beaches. The first hint of a radical change came Sunday afternoon when a helicopter pilot noted that the level of the Kupaianaha lava pond had dropped from its previous level of 50 feet below the rim to about 100 feet below. On Monday, another pilot discovered the level of the pond had dropped further, to about 200 feet. A drop like this hasn't been seen since the pond started forming. The low levels meant that no new magma was entering the pond from deep within the earth. Meanwhile, lava continued its normal process of draining out of the pond through an opening in its southern end. Through that opening, the lava enters a system of subserface tubes that carries it seven miles to the sea coast around Kupapau Point on the Puna coast. By late Monday, the lava flowing downhill in those tubes had drained out, and lava was no longer entering the sea. So, at the moment, it looks like the eruption may have come to a halt. However, some indications of deeper underground activity remain. The "hot spot" which feeds Kilauea lies about 40 miles deep. From there, magma rises to a large temporary storage chamber about 1.5 miles below Kilauea's summit. From there, it can go to various places; years ago it regularly fed the Halemaumau fire pit in the caldera at the summit; in recent years, other "plumbing" has been feeding the series of eruptions (including this last one) along one or more of Kialuea's rift zones along major ridges of the mountain. Movement of lava the hot spot into the storage chamber can be "heard" via "harmonic tremor" readings on the observatory's seismometers. They the harmonic tremor is still there, but has substantially decreased in amplitude to only about 30 percent of normal. This means that magma is still accumulating in the storage chamber and may flow out to the surface again, either at or near the lava pond site, or elsewhere on Kilauea. Tiltmeter measurements over the last few months indicate a gradual swelling of the summit of Kilauea, which presumably means that there is a considerable amount of magma in the storage chamber. At this point, one of three things may happen: harmonic tremor will continue to decrease, and tiltmeter readings will remain fairly steady, and 1) there might not be a further eruption...or, it is possible we may see some 2) brief renewal of activity, then no further activity for a year or more. Alternatively, if harmonic tremor comes back up to previous levels, we may see 3) a renewed sustained eruption, possibly some place else on Kilauea. No one knows for sure, but this just might be the end of the eruption. Bob Cunningham bob@loihi.hig.hawaii.edu
bob@uhmanoa.ics.hawaii.edu (Bob Cunningham) (04/29/88)
The Hawaii Volcano Observatory has officially noted the end of phase 48. However, they definitely think the eruption will continue, with another breakout of lava fairly soon. Bob Cunningham bob@loihi.hig.hawaii.edu
bob@uhmanoa.ics.hawaii.edu (Bob Cunningham) (05/05/88)
Famous last words.... Kilauea has started up again. The new activity is officially "Phase 49" of the eruption. The first indication of renewed activity was data from tiltmeter instrumentation on the weekend indicating that the summit of the volcano was beginning to deflate. This has become a reliable indication that magma is flowing in considerable volume from the storage chamber under the summit down to the rift zone. On Monday, a commercial helicopter pilot spotted that the Kupaianaha lava pond surface was rising by a hundred feet or more. Later in the day the lava pond filled up and began spilling out. Apparently the drainage tube at the south end of the pond that up until last week carried lava to the sea through the underground lava tube system is now blocked. So, lava began seeping out of the base of the former flows around the lava pond at six places, and is beginning to spread further on the surface in that area. Bob Cunningham bob@loihi.hig.hawaii.edu