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Report on Kilauea (United States) — September 1985


Kilauea

Scientific Event Alert Network Bulletin, vol. 10, no. 9 (September 1985)
Managing Editor: Lindsay McClelland.

Kilauea (United States) Episode 37 of the 1983-85 East Rift Zone eruption

Please cite this report as:

Global Volcanism Program, 1985. Report on Kilauea (United States) (McClelland, L., ed.). Scientific Event Alert Network Bulletin, 10:9. Smithsonian Institution. https://doi.org/10.5479/si.GVP.SEAN198509-332010



Kilauea

United States

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

All times are local (unless otherwise noted)


"Two episodes of high fountaining and lava production at the Pu`u `O`o vent occurred in September. Episode 36 occurred on 2 September. The distribution of episode 36 lava flows and the partly covered flows of episode 35 (July-August) are shown in figure 36. Episode 37 flows are unmapped as of this report. The total volume of lava produced by episode 35 was 11.7 x 106 m3. Episode 36 produced a lava volume of 11.5 x 106 m3.

EPISODE 37

"After a 22-day repose period, when the magma column in the Pu`u `O`o conduit was visible at depths of 50-80 m, the 37th episode occurred. Preceded by several small pahoehoe spillovers from intermittent fountains, the fountaining became continuous on 24 September at 1808. The level of eruption increased slowly to a peak between midnight and 0200 when fountain heights of approximately 250 m were estimated. Episode 37 ended as the fountaining died at 0619, having lasted 12 hours. The basalt, as in recent episodes, is microporphyritic with abundant olivine crystals (< 0.5 mm in diameter). The composition has remained unchanged since episode 32 in April.

"Summit deflation during episode 37, as recorded by the Uwekahuna tiltmeter (W-E), commenced on 24 September at 1900 (about an hour after lava fountaining became continuous) and ended at 0900 the next day, resulting in a net loss of 13.2 µrad.

"Tremor amplitude at the newly located seismometer near Pu`u `O`o increased on 24 September at about 2050 (2.5 hours after the onset of continuous lava fountaining), activating the tremor alarm at HVO at 2214. Tremor level decreased rapidly at 0619, coinciding with the end of fountaining. The decreased tremor following episode 37 assumed a pulsating pattern characterized by one-minute bursts of moderate amplitude alternating with several minutes of lower amplitude. This gas-piston pattern continued for about a day then changed to a more continuous background of low-amplitude harmonic tremor for the remainder of the month.

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: G. Ulrich, C. Heliker, R. Hanatani, and R. Koyanagi, HVO.