Report on Kilauea (United States) — July 1981
Scientific Event Alert Network Bulletin, vol. 6, no. 7 (July 1981)
Managing Editor: Lindsay McClelland.
Kilauea (United States) Intrusion under S summit area and SW rift zone
Please cite this report as:
Global Volcanism Program, 1981. Report on Kilauea (United States) (McClelland, L., ed.). Scientific Event Alert Network Bulletin, 6:7. Smithsonian Institution. https://doi.org/10.5479/si.GVP.SEAN198107-332010.
19.421°N, 155.287°W; summit elev. 1222 m
All times are local (unless otherwise noted)
"On 10-11 August seismographs and tiltmeters at HVO recorded a moderate intrusion at Kilauea. The event was characterized by an earthquake swarm and harmonic tremor, accompanied by summit deflation and ground cracking. As of 0800 on 11 August, an estimated 30-50 x 106 m3 of magma had intruded into the S summit and SW rift zones. The activity started with an increase of microearthquakes in the S summit area at 0330 on 10 August. Shortly before 0430 tiltmeters recorded the onset of the sharp summit deflation. By 0500 the seismic intensity increased and maintained a continuous state of activity. Micro-earthquakes and harmonic tremor less than 5 km in depth indicated that magma was migrating from the summit to the SW rift zone in the vicinity of the Kamakaia Hills nearly 20 km away. At mid-morning 11 August several thousand earthquakes of <= 4.5 Ms were detected, and monitoring instruments continued to record a diminishing pattern of seismicity and ground tilt."
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: R. Okamura, HVO.