Volcano Watch — Eruption provides dramatic viewing

The eruption from the episode 51 vents has continued without interruption since October 2. The flows crossed the Chain of Craters Road near Kamoamoa in Hawai`i Volcanoes National Park on November 7, covered part of the archaeological ruins and entered the sea during the evening of November 8. Since that time, flows have continued to pour into the sea and have created a new lava bench between the ocean and the black sand beach at Kamoamoa. This is the first time in more than a year that active flows have entered the ocean. These flows have reached the ocean because of the long duration of this eruptive interval; all the previous eruptive periods since February have been shorter than 32 days, and lava did not reach the ocean.

As we noted last week, lava entering the ocean produces several unique hazards, including explosions as the lava and seawater interact, hydrochloric acid fume, and sudden collapse of the lava benches that form on top of unstable sandy shoreline. Lava viewing will be safe and enjoyable if people are careful and observe the warning signs posted by the National Park Service in the Kamoamoa area.

The lava feeds of the flow advancing into the ocean through an underground tube, but upslope, this tube breaks open, and new surface flows occasionally occur. Lava has also been intermittently active over the small pali just above the Chain of Craters Road. This is a spectacular sight, particularly at night, as the lava cascades over the near-vertical pali. Several other flows have been active in the upper part of the pali and even above it. These flows are visible from the coast, mainly because of the smoke from small fires set by the active lava.

On Thursday, our scientists measured the volume of lava in the tube system near the vent and determined that about 100,000 cubic meters per day are passing through the tube. Because the top of the lava in the tube is nearly 13 meters below the surface of the lava field, making the measurements is difficult and less precise than obtaining them from the six-meter-deep tube downslope from Kupaianaha until last November, when we could no longer measure the rate of flow in that tube. The current volume is comparable to that from Kupaianaha shortly before the episode 49 eruption occurred last November and far below that at the peak of the eruption in 1988-1990. Despite the length of the currently active flow, the volume is relatively small and supports our previously expressed opinion that this nearly 10-year-long eruption continues to slowly wind down. It is also clear that magma continues to be supplied to Kīlauea's summit magma reservoir from the mantle below because the summit has not subsided as this volume of magma has been withdrawn and erupted along the rift zone. In other words, the lava erupted is being replaced by new magma from below at about the same rate at which it is being erupted.

The duration of this eruptive period appears to be related to the occurrence of a magnitude-4.3 earthquake on October 2, which modified the magmatic storage system in the vicinity of Pu`u `O`o. For the first time since the eruption migrated from Pu`u `O`o to Kupaianaha in mid-1986, the elevation of the eruptive vent is above that of the lava pond surface inside Pu`u `O`o. This observation suggests that lava erupting at the episode 51 vents is not first passing through the pond inside Pu`u `O`o, as we suspect it did throughout the activity at Kupaianaha and the episodes 49, 50, and 51 eruptions, and that activity may die out at Pu`u `O`o.

The field crew working along the tube system on Thursday was exposed to an unnecessary hazard when a commercial helicopter flew too close to them at low altitude. The air turbulence threw small fragments of glass into their faces, and the noise from the helicopter drowned out their communication. Being able to communicate with each other is important in such a hazardous environment. We appreciate the courtesy exhibited by most of the local pilots, and hope this article serves to inform those who might not be aware of the hazards they introduce to our scientists in the field.

The Observatory also had a seismic and tilt station near Heiheiahulu vandalized this past week. The stations are the eyes and ears of the Observatory and provide the data that we analyze to give the public warnings of volcanic activity. In this case, the batteries that power the transmitter were stolen, thereby making the station inoperable. This station is our first warning if magma were to migrate downrift from the current eruption site towards lower Puna. If you should happen across these stations while out hiking, please do not disturb them in any way. Their loss, even temporarily, greatly inhibits our ability to provide early warning of volcanic events that could affect your property or your lives.