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Report on Kilauea (United States) — September 1995


Kilauea

Bulletin of the Global Volcanism Network, vol. 20, no. 9 (September 1995)
Managing Editor: Richard Wunderman.

Kilauea (United States) Numerous lava flows upslope and on the coastal plain; new ocean entry formed

Please cite this report as:

Global Volcanism Program, 1995. Report on Kilauea (United States) (Wunderman, R., ed.). Bulletin of the Global Volcanism Network, 20:9. Smithsonian Institution. https://doi.org/10.5479/si.GVP.BGVN199509-332010



Kilauea

United States

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

All times are local (unless otherwise noted)


A large lava flow broke out of the E (Kamoamoa) tube on 1 August at 490 m elevation and cascaded down Pulama Pali (a fault scarp); by 3 August the flow had split into three lobes. The E flow was the most voluminous and advanced down the W side of the flow field as an aa/pahoehoe flow with multiple channels. The W flow was a large pahoehoe sheet flow with many active streams. The middle flow was an 1,800-m-long channelized aa/pahoehoe flow, but had stagnated by mid-August. On 17 August the W lobe cascaded over Paliuli and spread out along its base over the next five days. That same day the E lobe reached the coastal plain and on 18 August was within 200 m of the WHA seismometer, which was removed the next day. Two pahoehoe flows were noted upslope on 3 August, originating at ~660 and ~650 m elevation. The upper flow was not active on 11 August; however, the lower flow was still active and burning forest at 590 m elevation. The Highcastle ocean entry was active but variable in August, with mild explosive activity on 7-8 August. During sampling on 11 August, a lava stream visible through a skylight at ~635 m elevation was 15 m wide and 19 m deep. A lava flow 300-400 m long was active close to the 600-m elevation, but all flows and the Highcastle ocean entry stagnated when the eruption paused on the evening of 22 August.

The eruption resumed on 25 August, and the first flows broke out of the tube system at 660 m elevation. Later breakouts were noted at 600 and 510 m elevations. The tube system appeared to be reoccupied only as far as the 510-m elevation, from which point a large aa flow cascaded down the E side of the flow field. By the 28th, flows had advanced to 240 m elevation. By 29 August the Kamoamoa lava tube had been reoccupied as far as the top of Pulama Pali. Several surface breakouts burned kipukas above the pali, and numerous shallow skylights developed. On the slope of Pulama Pali, aa and channelized pahoehoe flows advanced in two major fronts down the E side of the Kamoamoa flow field, burning forest along the edge. The leading edge of these flows reached the base of Pulama Pali on 29 August and advanced as pahoehoe sheet flows toward the coast, entering the ocean on 7 September. Through 11 September, pahoehoe spilled into the ocean at several discrete locations in a zone ~200-300 m wide on the far E margin of the Kamoamoa flow field.

On 12 September, voluminous channelized and sheet flows were observed at the coast and on Pulama Pali; surface flows on the slope were limited to intermittent breakouts. These lava flows continued to burn forest along the E edge of the flow field. Pahoehoe sheet flows several hundred meters wide continued to enter the ocean at the E edge of the Kamoamoa flow field (Kamokuna) in late September. A new ocean entry 1 km W of the other flows (Kamoamoa) was established on 21 September. By 9 October a major ocean entry fed by a tube was well established at Kamokuna and generating a large plume from a diffuse, ~100-m-wide entry zone of surface pahoehoe flows; there was only minor explosive activity. Smaller, intermittent entries were observed farther W at Kamoamoa, where surface pahoehoe flows occasionally reached the ocean. On the slope of Pulama pali, most of the lava was traveling in tubes, though small surface flows were frequent.

The pond at Pu`u `O`o continued to shrink in early August, and a sluggish crust had formed over much of the pond; the only open areas were on the W and N edges. The pond remained locally crusted and fairly small in late August; it was often >95 m below the crater rim, but it rose slightly during the pause. Between 25 August and 1 September the pond rose ~30 m, but subsequently dropped back to around 100 m. During this interval very vesicular tephra were deposited on the crater rim. By 5 September, the lava pond had risen to 60 m, overlapping the old crater floor formed in February 1992, but again receded to ~100 m depth by 12 September. The level of the lava pond then remained unchanged at roughly 80 m below the crater rim through 9 October. Sloshing lava in the ~15-m-diameter circular pond occasionally overflowed onto the adjacent crater floor formed during August.

Eruption tremor levels along the East Rift Zone remained low, with sporadic bursts of higher amplitudes during 6-9 August. Microearthquake counts were high on 1-2 August, but were below average beneath the summit and rift zones through mid-month. Low-level tremor persisted until the evening of 22 August, when it decreased in amplitude. Amplitudes remained at nearly background levels until the morning of the 26th, gradually increasing to nearly 2x background. On 24 August, counts of shallow (LPC-A) and intermediate-depth (LPC-C) long-period earthquakes were high. The counts remained high through the 26th for the LPC-C events and through the 27th for the LPC-A events. On the evening of 24 August a shallow M 3.2 earthquake beneath the upper edge of the East Rift Zone was felt mildly by a few nearby residents. Eruption tremor levels were fairly high until early on 30 August. Tremor amplitudes in early September dropped to nearly background levels with bands of higher amplitudes of one-half to three hours duration.

The number of intermediate, long-period microearthquakes was high during 5-8 September (nearly 500 events). Tremor levels were relatively low during 12-25 September except for isolated higher-amplitude bursts. Eruption tremor amplitudes were ~2x background until 30 September. From 1 October, tremor levels dropped slightly, and by 4 October, banding patterns of low amplitudes alternating with higher amplitudes became apparent. Also, from 1 October, intermediate-depth long-period (LPC-C) earthquake counts began to increase. The most intense days were 5-7 October, with total daily counts of 167, 434, and 214, respectively; many were large enough to locate. Short-period microearthquake activity remained low to moderate beneath the summit and rift zones from August through early October.

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: Tari Mattox and Paul Okubo, Hawaiian Volcano Observatory (HVO), U.S. Geological Survey, Hawaii Volcanoes National Park, HI 96718, USA.