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Report on Kilauea (United States) — September 1988


Kilauea

Scientific Event Alert Network Bulletin, vol. 13, no. 9 (September 1988)
Managing Editor: Lindsay McClelland.

Kilauea (United States) Littoral explosions and lava bench collapse

Please cite this report as:

Global Volcanism Program, 1988. Report on Kilauea (United States) (McClelland, L., ed.). Scientific Event Alert Network Bulletin, 13:9. Smithsonian Institution. https://doi.org/10.5479/si.GVP.SEAN198809-332010



Kilauea

United States

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

All times are local (unless otherwise noted)


The . . . eruption continued to feed lava into the ocean near Kupapau Point. Fluctuating tremor associated with explosive lava entry into the sea was recorded 3 km away at Wahaula seismic station. Tube system surface outbreaks occurred on 19 and 20 September above the fault scarp at ~350 m elevation. The 19 September outbreak fed 1-km-long aa flows that stagnated the same day. The lava pond level at Kupaianaha remained 20 m below the N crater rim and lava was occasionally seen in Pu`u `O`o crater's main vent. Additional lava bench collapses occurred, with major episodes on 6, 15, and 26 September. Lava bench collapse was detected seismically as a series of high-amplitude bursts followed by smaller rockfall and explosion signals and a temporary decrease in tremor. At 2038 on the 26th, 1/3 to 1/2 of the 200-m-long and 50-70-m-wide bench collapsed. Strong explosions built a pair of littoral cones (4-5 m high) on the resulting collapse scarp. A new bench grew rapidly, and by 10 October, two small new cones (2-3 m) had built 20-30 m seaward. Small spits grew in front of the cones. Increased pyroclastic activity in early October covered 1/3 of the bench's western area with several centimeters of tephra and added to a pre-existing 250-m-long tephra blanket that covered the nearby beach.

Low-level tremor continued . . . near Pu`u `O`o and Kupaianaha. At Kīlauea's summit, the number of short period microearthquakes was relatively steady at ~100/day. Two moderate swarms of intermediate-depth (6-15 km), long-period earthquakes occurred 4-6 and 26-27 September and consisted of several hundred events (M>0.1). The month's largest event (M 4.4) at 1952 on 12 September was centered 11 km beneath Kīlauea's S flank and was widely felt in the S part of the island. No structural damage was reported.

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 and R. Koyanagi, HVO.