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Report on Kilauea (United States) — July 1987


Kilauea

Scientific Event Alert Network Bulletin, vol. 12, no. 7 (July 1987)
Managing Editor: Lindsay McClelland.

Kilauea (United States) Tube system blockage changes shield, lava flows

Please cite this report as:

Global Volcanism Program, 1987. Report on Kilauea (United States) (McClelland, L., ed.). Scientific Event Alert Network Bulletin, 12:7. Smithsonian Institution. https://doi.org/10.5479/si.GVP.SEAN198707-332010



Kilauea

United States

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

All times are local (unless otherwise noted)


Considerable change occurred during July at the East-rift shield surrounding the active vent. At the beginning of the month, lava continued to flow toward the S coast, slowly entering the ocean along the E edge of the lava field. The tube system feeding the March-June flows became blocked close to the lava pond and by 4 July all of the flows at the coastal area were stagnant. Most of the activity was confined to the vent area. Lava continued flowing from the neck of the lava pond on the 48-m-high shield, but piled up on the SE flank, forming a lava mound. That activity ceased as lava emerged from the base, W of the previous tube outlet and flowed along the W side of the lava field. The level of the lava pond fluctuated from overflowing or nearly full to as much as 10 m below its rim.

By 14 July the longest flows extended to 530 m elevation, 3.5 km SE of the vent, and moved slowly downslope to 350 m, 4 km from the vent by the 22nd. There the slope steepens and the main lava flow advanced rapidly to ~90 m elevation before stopping on 26 July. The terminus of the flow was 8 km from the vent and consisted of small, multiple aa lobes. Several of the small aa flows came within 0.3 km of Royal Gardens Subdividion, causing concern for some of the remaining residents, but it stagnated before any property was damaged.

The main tube-fed pahoehoe flow was advancing slowly over the aa and had reached 45 m elevation by 29 July, ~9 km from the vent and < 2 km from the coastline. No dwellings were threatened. Lava supply to the flow front had significantly diminished 21-28 July and the lava pond was overflowing. On 30 July, the tube system became completely blocked near the vent and all lava supply to the current flow ceased. Activity resumed near the vent and by early August channel-fed pahoehoe emanating from the base of the shield had covered the upper 2 km of the previous flow.

Harmonic tremor continued at low levels . . . near Pu`u `O`o and the current eruptive vent. Shallow microearthquakes associated with structural adjustments to Pu`u `O`o occurred at a gradually decreasing rate following the moderate collapse event of 26 June. The number of microearthquakes was about average in the summit region. Most of the July earthquakes occurred at <10 km depth on the SE flanks of Kīlauea and Mauna Loa with magnitudes ranging from 0.5 to 4.3.

The summit tiltmeter indicated some minor short-term inflation, but no long-term trend has been established . . . .

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.