Report on Kilauea (United States) — September 1986
Scientific Event Alert Network Bulletin, vol. 11, no. 9 (September 1986)
Managing Editor: Lindsay McClelland.
Kilauea (United States) Lava tubes feed flow complex; continued lava shield growth
Please cite this report as:
Global Volcanism Program, 1986. Report on Kilauea (United States) (McClelland, L., ed.). Scientific Event Alert Network Bulletin, 11:9. Smithsonian Institution. https://doi.org/10.5479/si.GVP.SEAN198609-332010.
19.421°N, 155.287°W; summit elev. 1222 m
All times are local (unless otherwise noted)
The eruptive episode . . . continued into October, building a new pahoehoe lava shield ~3 km NE (downrift) of Pu`u `O`o, the vent active in most of the 47 previous episodes. The estimated lava output rate since 20 July is ~0.5 x 106 m3/day. The new shield grew 10 m in height during September, to 44 m high and 1,600 m across by the end of the month. Activity from the shield's W vent stopped by mid-September, but lava production was continuous through a 150-m lava pond in the shield's E vent. Depth of the pond varied by no more than 3 meters. Through most of September, the activity fed a series of small pahoehoe flows that did not extend much beyond the margin of the shield. A lava tube system formed in late September, feeding lava flows that advanced SE at irregular rates of as much as 0.5 km/day. At the end of September, a thin broad flow front was 4 km from the vent, and by 8 October a complex network of tube-fed flows occupied a broad area between the westernmost 1977 lava and the longest April 1984 flow. The conduit at Pu`u `O`o remained open and incandescent, with flaming gases visible at night.
Low-level harmonic tremor was continuous, with minor fluctuations in amplitude. No well-defined trends were detected by the summit tiltmeter, and some of the measured variation may have been instrument response to heavy rains (figure 45).
Geologic Background. Kilauea, which overlaps the E flank of the massive Mauna Loa shield volcano, has been Hawaii's most active volcano during historical time. Eruptions are prominent in Polynesian legends; written documentation extending back to only 1820 records frequent summit and flank lava flow eruptions that were interspersed with periods of long-term lava lake activity that lasted until 1924 at Halemaumau crater, within the summit caldera. The 3 x 5 km caldera was formed in several stages about 1500 years ago and during the 18th century; eruptions have also originated from the lengthy East and SW rift zones, which extend to the sea on both sides of the volcano. About 90% of the surface of the basaltic shield volcano is formed of lava flows less than about 1100 years old; 70% of the volcano's surface is younger than 600 years. A long-term eruption from the East rift zone that began in 1983 has produced lava flows covering more than 100 km2, destroying nearly 200 houses and adding new coastline to the island.
Information Contacts: C. Heliker, HVO.