Report on Kilauea (United States) — October 1983
Scientific Event Alert Network Bulletin, vol. 8, no. 10 (October 1983)
Managing Editor: Lindsay McClelland.
Kilauea (United States) 10th and 11th major phases of E Rift Zone eruption
Please cite this report as:
Global Volcanism Program, 1983. Report on Kilauea (United States). In: McClelland, L. (ed.), Scientific Event Alert Network Bulletin, 8:10. Smithsonian Institution. https://doi.org/10.5479/si.GVP.SEAN198310-332010.
19.421°N, 155.287°W; summit elev. 1222 m
All times are local (unless otherwise noted)
"The 10th major episode of Kilauea's prolonged E rift zone eruption occurred in early October. As in episodes 4-9, the active vent was at the growing spatter cone, now tentatively named Pu'u O [later Pu`u `O`o, see 10:4], approximately 750 m NE of Pu'u Kamoamoa (figure 20).
|Figure 20. Distribution of Kilauea lavas and vent deposits of episodes 8, 9, and 10. Courtesy of HVO.|
"Low-level eruptive activity marking the onset of episode 10 began at about 0800 on 2 October when a small lava flow, about 300-500 m3 in volume, was extruded onto the floor of the crater within Pu'u O. Some of the lava drained back into the open, glowing, 4-m-diameter conduit, which had been preserved near the center of the crater floor at the end of episode 9. No further activity was observed until 4 October when small bursts of spatter were intermittently emitted, most of which fell back into the conduit.
"Beginning at about 0100 on 5 October, harmonic tremor increased above the low repose-period background level, and lava began to spill through a deep breach in the NE wall of the spatter cone. Intensity of both harmonic tremor and eruptive activity increased over the next several hours. By 0330, tremor amplitude had increased by an order of magnitude, and by 0400 the glow was visible and the roar of the vent was audible 20 km away at HVO. Near dawn, the 300-m-high fountain was visible from the coast at the Wahaula Visitor Center (approximately 11 km S of the active vent). Late on 5 October, tremor amplitude increased to a maximum exceeding that of the previous eruptive episode, consistent with a trend of progressively increasing tremor that began with episode 4. High tremor occurred throughout vigorous episode 10 lava emission.
"After initially high activity, the fountains became erratic, changing rapidly in height from a few tens of meters to a maximum of about 250 m. At times, 3-4 distinct fountains were observed within the crater; sometimes high jetting fountains and a relatively low dome fountain played simultaneously from different parts of the lava pond surface.
"On 5-6 October, a thick slow-moving aa flow advanced 3.7 km ESE from Pu'u O, and rapidly moving pahoehoe formed superimposed sheets over an elongated area that extended about 2 km from the vent. By 7 October, the aa flow had stagnated, and the pahoehoe issuing to the NE had become confined to a channel in which a vigorously flowing lava river supplied a flow of pahoehoe and aa that eventually extended 4 km NE (figure 21).
"Eruptive activity waned between about 1630 and 1700 on 7 October; harmonic tremor amplitude decreased rapidly at about 1650, and, after 1700, assumed the low level typical of repose-period activity. Such low-level tremor continued in the E rift zone for the remainder of October.
"As in the previous several episodes, episodes 10 basalt is characterized by the occurrence of scattered small olivine phenocrysts. Lava temperatures measured by thermocouple ranged from 1134° to 1142°C; the latter is the highest lava temperature measured since the beginning of eruptive activity on 3 January.
"Episode 10 produced nearly 14 x 106 m3 of lava for a total erupted volume since 3 January of approximately 120 x 106 m3 distributed over about 23 x 106 m2 of the rift zone. At the end of episode 10, Pu'u O was approximately 600 m in diameter and 80 m high. A chaotic jumble of disrupted blocks of agglutinated spatter covered the crater floor and the spillway through which the NE flow exited. The blocks, which were apparently transported as the last lava drained back into the eruptive conduit, choked the central conduit, which had stood open after episode 9. Oxidized fume issued from the margins of the crater floor and from the nearby parts of the interior walls of the crater but not from the rubble-covered floor.
"During episode 10, summit subsidence was recorded by nearly 19 µrad of ESE tilt change at the Uwekahuna vault on the NW rim of the caldera. This corresponds to a summit volume decrease of about 7.5 x 106 m3, bringing the total deflationary volume loss since January to about 130 x 106 m3. Summit inflation from the end of episode 10 to the end of October was sufficient for the Uwekahuna tiltmeter to more than recover the deflationary tilt change of episode 10."
Addendum: Episode 11 began with an increase in harmonic tremor amplitude at 2314 on 5 November and the onset of eruptive activity around midnight. Summit deflation began at about 0200 on 6 November. An overflight at 0730 revealed a discontinuous line of fountains up to 40 m high extending approximately 200 m up and down rift from the spatter cone (Pu'u O) active in previous eruptive episodes. Vents high on the W flank of the spatter cone fed 2 lava flows which that 4 and 1.5 km S before activity ceased there late on 6 November. The main vent, on the E summit and flank of the spatter cone, produced lava fountains 10-40 m high and fed the main lava flow that extended 8 km NE [it reached 9.5 km length; 8:11]. At 1840 on 7 November, the amplitude of harmonic tremor decreased sharply; lava fountaining from the main vent ceased later on 7 November, and inflation of the summit region resumed.
Geologic Background. Kilauea, which overlaps the E flank of the massive Mauna Loa shield volcano, has been Hawaii's most active volcano during historical time. Eruptions are prominent in Polynesian legends; written documentation extending back to only 1820 records frequent summit and flank lava flow eruptions that were interspersed with periods of long-term lava lake activity that lasted until 1924 at Halemaumau crater, within the summit caldera. The 3 x 5 km caldera was formed in several stages about 1500 years ago and during the 18th century; eruptions have also originated from the lengthy East and SW rift zones, which extend to the sea on both sides of the volcano. About 90% of the surface of the basaltic shield volcano is formed of lava flows less than about 1100 years old; 70% of the volcano's surface is younger than 600 years. A long-term eruption from the East rift zone that began in 1983 has produced lava flows covering more than 100 km2, destroying nearly 200 houses and adding new coastline to the island.
Information Contacts: E. Wolfe, A. Okamura, and R. Koyanagi, HVO.