Volcano Watch — Kīlauea eruption status after pause

Kīlauea's 13-year-long eruption restarted on Valentine's day after a nine-day-long pause in activity. The renewed activity began about midnight on February 13 with changes in the ground vibrations recorded near the Pu'u 'O'o vent. A rise in the level and activity of the lava lake inside the cone resulted in a bright glow above the cone during the evening.

By about 2:00 a.m. on February 14, lava was issuing from the previously active vents on the flanks of the cone, flowing through the same lava tube towards the south, and breaking out to form new surface flows. These flows resulted in an extremely bright glow that was reported to us by a number of insomniacs.

Early the following morning, we received reports from helicopter pilot David Okita that flows had broken out of a number of skylights in the old tube, with the lowest-elevation breakout from about the 1,300-foot level. A large 'a'a flow was advancing downslope from this breakout while other upslope breakouts were entering the forest on both the east and the west sides of the Kamoamoa flowfield, igniting the vegetation. These fires produced large smoke plumes that were particularly noticeable around noon.

The combined eruptive volume from these various flows was close to normal eruptive levels and far less than was produced during the surge in activity on February 1 and 2 that preceded the pause. By the morning of February 15, lava had reoccupied the entire tube and was entering the ocean at Kamokuna.

Following previous pauses in activity, the lava tube has not been reoccupied for nearly so great a distance, and we had not expected it to utilize the Kamokuna tube to the ocean. Rain normally enhances the cooling of the tubes during pauses, and we suspect that the reoccupation of this tube was, in part, due to the dry weather throughout the pause.

As of the afternoon of the 15th, only about one-third of the lava was flowing to the ocean through the tube, with the remainder forming surface flows on the east side of the flow field above Kamoamoa.

During the surge in activity of February 1 and 2, new 'a'a flows advanced rapidly down the slope from numerous breakouts. The map shows these flows and the Kamoamoa flow field (1992-1996) with the earlier flows from the eruption. The flows erupted between 1983 and 1986 are 'a'a flows fed from high fountains at Pu'u 'O'o, whereas the flows erupted from 1986 to 1992 are tube-fed pahoehoe flows erupted at Kupaianaha.

We measured higher than normal ratios of carbon dioxide to sulfur dioxide at fumaroles near Halema'uma'u during and after the earthquake swarm on February 1. The large gas emission also resulted in the extremely poor air quality during this period. Fortunately, during the long pause, the emission of sulfur dioxide from Kīlauea decreased sharply and produced some of the clearest days in many months.

The longer-than-normal pause in eruptive activity from February 4-14 was proably related to the earthquakes warm and changes at Kīlauea's summit that took place during the morning of February 1. However, the changes in earthquake and deformation near the summit during the pause were typical of previous pauses. The events of February 1 may have been triggered by the rapid release of carbon dioxide bubbles from magma stored beneath the summit of Kīlauea.

If the complete analysis of the seismic and geodetic data and the chemical analyses of the lavas and gases we collected during this event supports this idea, we may be much closer to understanding the trigger that initiates eruptions at basaltic volcanoes.