Report on Kilauea (United States) — August 1980
Scientific Event Alert Network Bulletin, vol. 5, no. 8 (August 1980)
Managing Editor: David Squires.
Kilauea (United States) Intrusion into the upper east rift zone
Please cite this report as:
Global Volcanism Program, 1980. Report on Kilauea (United States) (Squires, D., ed.). Scientific Event Alert Network Bulletin, 5:8. Smithsonian Institution. https://doi.org/10.5479/si.GVP.SEAN198008-332010.
19.421°N, 155.287°W; summit elev. 1222 m
All times are local (unless otherwise noted)
Magma was intruded into the upper E rift zone on 27 August, the first intrusive activity there since March. As in the two March intrusions, no eruption took place. An earthquake swarm began near Puhimau Crater (about 1.5 km SE of the caldera rim) at 1425 on 27 August. Within 6 minutes, the number of microearthquakes had increased to several per minute. Summit deflation started 30 minutes after the swarm, at 1455.
The earthquakes migrated generally downrift at about 1 km/hour. Several were felt nearby, with the three highest magnitudes ranging from 3.6 to 4.0. Hundreds of magnitude 1-3 events occurred at depths of 1-4 km. The seismographs closest to the swarm apparently registered some shallow volcanic tremor, but microearthquakes occurred so rapidly that tremor was obscured on the records. The number of microearthquakes per minute started to decrease at about 1830 and the swarm ended early the next morning. Summit deflation had stopped at about 1930 on 27 August, after 7.5 µrad of tilt had been recorded.
The USGS interpreted the activity as the formation of a dike estimated to be about 3 km long, 1-2 km high, and l m wide, located 1-3 km beneath the surface. About 4 x 106 m3 of magma were calculated to have been injected into the dike between 1500 and 1930 on 27 August.
SO2 emission was detected in the Puhimau thermal area (where the earthquake swarm began) on 28 August. The CO2/SO2 ratios of gases emitted by the summit fumaroles before and after the intrusion remained about the same as the previous week.
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: Hawaiian Volcano Observatory, USGS.