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Report on Kilauea (United States) — March 1985


Kilauea

Scientific Event Alert Network Bulletin, vol. 10, no. 3 (March 1985)
Managing Editor: Lindsay McClelland.

Kilauea (United States) Episode 31; lava flows into subdivision; tephra builds Pu`u `O`o

Please cite this report as:

Global Volcanism Program, 1985. Report on Kilauea (United States) (McClelland, L., ed.). Scientific Event Alert Network Bulletin, 10:3. Smithsonian Institution. https://doi.org/10.5479/si.GVP.SEAN198503-332010



Kilauea

United States

19.421°N, 155.287°W; summit elev. 1222 m

All times are local (unless otherwise noted)


EPISODE 31

"The 1983-85 eruption produced the 31st episode of vigorous fountaining and continuous lava production on 13-14 March. Sustained high-level activity began on 13 March at 0720 and continued for almost 21.5 hours. Fountain heights reached a maximum of 340 m above the Pu'u O conduit 5 hours after the eruptive episode began. A single broad aa flow advanced 4 km SE before splitting into two lobes. The E lobe entered Royal Gardens subdivision on 14 March at 0100; no buildings were damaged, although the lava passed within 200 m of one house and eventually stagnated within 150 m of another. The W lobe extended 7.8 km from the vent, to about 90 m elevation (within the National Park).

"Heavy tephra fall occurred on the SW side of Pu'u O, adding 11 m to its height. At the end of episode 31, the summit elevation was 924 m above sea level and 205 m above the pre-1983 surface. The volume of lava produced during episode 31 was approximately 19 x 106 m3, with an estimated tephra volume of 0.2 x 106 m3 (dense rock equivalent). The basalt of episode 31, like that of recent episodes, is microporphyritic, with about 2.6 modal % olivine microphenocrysts (< 1 mm).

"Following episode 31, dense fume obscured the view into the conduit of Pu'u O, and the magma column was not seen for the remainder of March.

Deformation. "Rapid summit subsidence associated with episode 31 began at approximately 0700 on 13 March, about as high-level eruptive activity began. The Uwekahuna (W-E) tiltmeter recorded continuous summit subsidence until 0600 the next day. The net tilt loss was 20.4 µrad. The maximum rate of deflation, 2.3 µrad per hour recorded between 1200 and 1300 on the 13th, was the highest recorded since the episode 1 intrusion. As at the end of episode 30, reinflation of the summit began slowly, and by the end of March the summit tilt had recovered 4.7 µrad.

Seismicity. "The intensity of harmonic tremor recorded at the Kamoamoa seismic station near Pu'u O increased rapidly starting on 13 March at 0600. By the start of vigorous eruptive activity at 0720, tremor had reached a high amplitude that was sustained until the end of the episode at 0458 the next day. Following episode 31, tremor amplitude dropped to the low level characteristic of inter-episode periods. Fluctuating low-level tremor continued in the middle E rift zone for the rest of March, with variation in amplitudes occurring at intervals of a few minutes to several days."

Geological Summary. Kilauea overlaps the E flank of the massive Mauna Loa shield volcano in the island of Hawaii. Eruptions are prominent in Polynesian legends; written documentation since 1820 records frequent summit and flank lava flow eruptions interspersed with periods of long-term lava lake activity at Halemaumau crater in the summit caldera until 1924. The 3 x 5 km caldera was formed in several stages about 1,500 years ago and during the 18th century; eruptions have also originated from the lengthy East and Southwest rift zones, which extend to the ocean in both directions. About 90% of the surface of the basaltic shield volcano is formed of lava flows less than about 1,100 years old; 70% of the surface is younger than 600 years. The long-term eruption from the East rift zone between 1983 and 2018 produced lava flows covering more than 100 km2, destroyed hundreds of houses, and added new coastline.

Information Contacts: C. Heliker, R. Hanatani, R. Koyanagi, HVO.