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Report on Kilauea (United States) — February 1983


Kilauea

Scientific Event Alert Network Bulletin, vol. 8, no. 2 (February 1983)
Managing Editor: Lindsay McClelland.

Kilauea (United States) Renewed fountaining and lava flow production on E Rift

Please cite this report as:

Global Volcanism Program, 1983. Report on Kilauea (United States) (McClelland, L., ed.). Scientific Event Alert Network Bulletin, 8:2. Smithsonian Institution. https://doi.org/10.5479/si.GVP.SEAN198302-332010



Kilauea

United States

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

All times are local (unless otherwise noted)


"The E rift zone eruption of Kīlauea that began on 3 January resumed on 10 February, and lava production continued until 4 March along eruptive fissures established during the initial outbreak on 3 January (figure 17). The renewed eruption followed nearly a month in which vent activity was limited largely to incandescence and emission of burning gases along parts of a 2-km segment of the vent system that extended E from about 0.75 km NE of Pu'u Kamoamoa to the area S of Pu'u Kahaualea. During the quiet period, a little incandescant spatter was ejected sporadically from the E vents; at least some of the ejecta consisted of wallrock remelted and eroded from the vents by vigorous emission of burning gas. There was no measurable production of new lava.

"Increased spatter production was first recognized on 10 February; a small (6 m-high) spatter cone had formed at the E vents (0.7 km S of Pu'u Kahaulea). By 12 February, a second small spatter cone had formed, and a glowing crack extended tens of meters NE of the 2 cones. Subsequent intermittent production of low fountains and small lava flows through 24 February led to growth of a flat-topped shield estimated to be about 200 m long, 100 m wide, and 10 m thick. The shield was capped by a 170 m-long line of juxtaposed spatter cones ranging up to about 15 m high. Lava production during the 2-week shield-building period is estimated at 0.5 x 106 m3. In addition, a short (probably 10-minute) episode of spatter production occurred at a vent just E of Pu'u Kamoamoa at about 2220 on 19 February. Gas emission during this period was low and was characterized by extremely low atomic C/S ratios (approximately 0.05) suggesting that the near-surface magma had largely degassed during the non-eruptive interval.

"Beginning at 0145 on 25 February, fountaining and lava flow production increased in the W and central parts of the shield and a flow about a kilometer long extended NE. Gas composition also changed at this time, becoming more C-rich (C/S approximately 0.15) and generally reverting to a composition indistinguishable from that of the early January gases. Thirteen hours later, at about 1440 on 25 February, the main eruptive locus shifted about 100 m uprift and eruption from the shield vents soon terminated, at 1518. Fountains played continuously at this new locus until the end of the eruptive episode on 4 March. During this period, sporadic lava production also occurred from local vents as far uprift as 0.75 km NE of Pu'u Kamoamoa.

"During its week of sustained activity, the main fountain, about 0.75 km SSW of Pu'u Kahaualea, was commonly 40-80 m high. Estimated to be about 30 m wide at its base, the fountain arose from a lava pond about 60 m in diameter. By the evening of 25 February, the S rim of the levee containing the lava pond had developed a spillway through which 2 major flows were supplied during the ensuing week. One of these moved NE 25-26 February within the same graben that contained the upper part of the 7 January flow. Following the path of that earlier flow, the new flow turned SE about 0.5 km W of Kalalua and stopped about 3 km from its source.

"By the morning of 27 February, the active lava river leading from the pond had been diverted SE, producing a flow that eventually extended more than 7 km from the vent to its terminus, about 3.8 km from the coast. This latest flow, parallel to and a kilometer SW of the 7 January flow, advanced slowly through the rain forest until 4 March, when lava production stopped. In the half nearest the vent, where the feeding channel was largely pahoehoe, the average velocity of the advancing flow front was about 90 m/hour. In the lower half, where the flow was dominantly aa, the front advanced episodically, but at an average rate of about 30 m/hour, even on the steepest (about 7°) slopes.

"In the early evening of 2 March, the advancing aa front, locally up to 10 m thick, entered the NE part of a sparsely populated subdivision on the S flank, just E of Hawaii Volcanoes National Park. Two dwellings were destroyed before lava production at the vent stopped at about 1500 on 4 March. Subsequent movement in the distal part of the flow was limited to minor adjustments that led to only a few meters of additional lava advance.

"Preliminary estimates, as yet without benefit of careful mapping or methodical thickness measurements, indicate that about 10 x 106 m3 of lava were extruded 10 February-4 March. Thermocouple measurements in pahoehoe toes gave lava temperatures of about 1112°-1120°C, slightly cooler than in January. The basalt is sparsely porphyritic with scattered small phenocrysts of olivine and plagioclase.

Seismicity and deformation. "Apparently because the feeder dike system had become fully established in early January and was maintained until eruptive activity resumed in February, the renewed lava emission was not accompanied by increased numbers of shallow earthquakes in either the summit or E rift zone. Harmonic tremor had declined by 30 January to about 10% of its high amplitude in early January; originating from a source beneath February's eruptive vents, the tremor slowly doubled in amplitude 30 January-25 February. From 25 February-4 March, average tremor amplitude was about 30% of the early January level. On 4 March, when lava production terminated, the tremor amplitude dropped abruptly to a low, but constant, level that was continuing as of 10 March.

"By 25 February, the E-W component tiltmeter in Uwekahuna Vault near the summit had recorded approximately 9 µrad of gradual summit re-inflation following the major subsidence of early January. The vigorous eruptive activity 25 February-4 March in the middle E rift zone coincided with an 11 µrad E-W deflation at Uwekahuna. Rapid summit re-inflation averaging about a µrad per day has occurred 4-10 March.

"No significant extension across the E rift has occurred in the vicinity of Kalalua since the major eruption of 7 January. However, a survey line across the eruptive fissure near Pu'u Kahaualea showed extension 29 January-12 February of at least 13 mm/day. By 14 February, new lava had obstructed the line."

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: E. Wolfe, A. Okamura, R. Koyanagi, HVO.