Volcano Watch — East Rift eruption continues at low, steady level

The eruption on the East Rift Zone of Kīlauea Volcano continues with low-volume, steady effusion of lava from the breakout at about the 1,900-foot level of the tube downslope from the Kupaianaha vent. This is the same area that has had active flows for the last several weeks. Tremor continues at low levels in the upper East Rift, indicating that magma continues to move in the rift zone. 

The summit has undergone short periods of inflation and deflation during the last two weeks, but there has been no significant net change in the level of inflation. The volume of lava traveling down the tube to the eruption site continues to decline slowly and is now less than 50,000 cubic yards per day. The lava pond within Pu`u `O`o has been quite active, as seen by the bright glow at night and the occurrence of short bursts of more intense tremor recorded on nearby seismograph stations. There have been no earthquakes with magnitudes greater than 3.0 this past week. 

As the eruption wanes, the volume of fume emitted by the volcano is also declining. The volcanic fume emitted from Kīlauea consists mainly of water, carbon dioxide, and sulfur dioxide. Of the three, sulfur dioxide is the component that is the main irritant and the source of vog. Fume is emitted from both the summit and from the eruption site as the erupting lava degasses. 

Before the current eruption began in early 1983, about 170 tons of sulfur dioxide per day were emitted from the summit of Kīlauea; this was nearly all the sulfur emitted from Kīlauea. For the early parts of the eruption in 1983 and 1984, the amount of sulfur dioxide emitted at the summit increased to about 275 tons per day. By 1987 and 1988, the amount of sulfur dioxide emitted had peaked at perhaps 330 tons per day at the summit. In 1991, the amount has declined to about 275 tons per day. The amount of sulfur dioxide emitted at and near Pu`u `O`o is considerably larger. The maximum amount, again in 1987 and 1988, was about 1,200 tons per day from Pu`u `O`o and perhaps several hundred additional tons per day from Kupaianaha and from the skylights along the tube system. During 1987 and 1988, the total amount of sulfur dioxide emitted from Kīlauea Volcano was at least 1,750 tons per day. The Pu`u `O`o vent was emitting about 800 tons per day last August, for a total from Kīlauea Volcano at that time of perhaps 1,250 tons per day or 450,000 tons per year. We have no measurements of the amount of sulfur dioxide from Pu`u `O`o since August, but we suspect the amount has decreased, along with the volume of erupted lava. In comparison, the main eruption at Mt. Pinatubo in the Philipines on June 15, 1991 emitted 19 million tons of sulfur dioxide, or roughly four times the total amount emitted by Kīlauea Volcano since this eruption began in early 1983.

Sulfur dioxide from Kīlauea causes air quality problems on the Big Island and haze throughout the Islands. An air quality monitoring station near the Park Headquarters in Hawai`i Volcanoes National Park has exceeded the standard set by the Environmental Protection Agency for sulfur dioxide (0.14 parts per million) 50 times between 1987 and 1990. The EPA standard is exceeded roughly 22 days a year, or 6 percent of the time. 

The day-to-day fluctuations in sulfur dioxide emissions are small and do not account for the variations in VOG on the Island. Away from the summit of Kīlauea Volcano, the severity of VOG is mainly due to the direction and velocity of the prevailing winds.