Volcano Watch — Eruption's changed little after more than 11 years

The eruption on Kīlauea's east rift zone continues with little change. The eruption has now been going for eleven and one-half years and shows no signs that the end is close.

The eruption has produced about 1 cubic kilometer (1,000 million cubic meters) of lava during this time. Several astute readers noted that the volume was incorrected reported in this column a few weeks ago. Two active vents are located on the south and west flanks of the Pu'u 'O'o cone, which also contains an active lava lake. The lava erupted from the two vents travels underground in lava tubes to a point about one-half mile south of Pu'u 'O'o, where the two tubes combine into a single tube. There is a single skylight, or hole, in the top of the upper part of the tube at about 2,350 feet elevation.

Lava can be seen flowing within the tube through the top of this skylight. Additional skylights occur along the tube below 450 feet elevation. Most of these are ephemeral, but new skylights open about as often as old skylights seal over.

In the past few weeks, the eruption has been characterized by numerous surface flows, generally starting from breaks in the tube below 450 feet. These flows advance and cascade over Paliuli, sometimes forming spectacular lava falls. Most of the activity is along the western edge of the flow field and so is visible from the end of Chain of Craters Road inside Hawaii Volcanoes National Park. These surface flows are probably caused by surges in the eruption when more lava enters the tube than it can accommodate; the excess forces its way through weak points in the tube roof and forms surface flows.

Throughout this period, lava has flowed into the ocean near the western edge of the flow field near Laeapuki. The flows have been building new land seaward of the Laeapuki lava flow that was active in April 1993. The ocean entries are also easily visible from the end of Chain of Craters Road. The ocean activity has slowly consolidated from a broad entry, more than 1,600 feet wide, to a narrower zone of activity about 500 feet wide. There have been periods of explosive activity at the ocean entries that have produced lava fountains as high as 150 feet, though more typical activity has lava sprays up to 40-50 feet high. At times, the explosions can be heard from the end of the road and are energetic enough to be recorded on a seismometer located several miles to the east, between the Kamoamoa and the Wahaula flows.

The coastline has extended about 300 feet seaward from the seacliff formed during emplacement of the Laeapuki flow. This region of new land is very hazardous, as these new lava ledges occassionally slide into the ocean as small landslides, usually with little or no warning. Cracks that are parallel to the coast have formed within this lava ledge and were first noticed on June 3. Failure of the ledge may remove the entire ledge back to these cracks, or even beyond. The explosions vary in size and can spray incandescent blocks and spatter anywhere within a few hundred meters of the entries. For your safety, obey all National Park Service area closure signs and watch from a safe distance.

I will be going on a long business trip/vacation to the mainland, so the Volcano Watch column will not appear again until late July, when I return. If there are dramatic changes in the eruption, the staff at the U.S. Geological Survey's Hawaiian Volcano Observatory will provide updates.