Report on Kilauea (United States) — April 1993
Bulletin of the Global Volcanism Network, vol. 18, no. 4 (April 1993)
Managing Editor: Edward Venzke.
Kilauea (United States) Lava continues to enter the ocean
Please cite this report as:
Global Volcanism Program, 1993. Report on Kilauea (United States) (Venzke, E., ed.). Bulletin of the Global Volcanism Network, 18:4. Smithsonian Institution. https://doi.org/10.5479/si.GVP.BGVN199304-332010
19.421°N, 155.287°W; summit elev. 1222 m
All times are local (unless otherwise noted)
The . . . eruption continued in April and early May as lava from E-51 and E-53 vents entered the ocean. Surface flows were rare during the second half of April, but lava continued to reach the coastline through tubes. The volume of lava entering the ocean at Lae Apuki and along the W edge of the Kamoamoa delta began to decline in the last few days of April and early May as surface flows began breaking out inland from the entry points. By 6 May only the W Kamoamoa entry remained slightly active. The same day, three large breakouts were observed on Pulama Pali and two large sheet flows appeared on the coastal plain at night. One flow emerged from a tube below Pali Uli (~1 km inland) and advanced down the W side of the Lae Apuki flow. The other flow broke out of the Kamoamoa lava tube and covered new land on the E margin of the Kamoamoa flow field. By 10 May, the flows at Lae Apuki were stagnant, but lava continued to enter the ocean on both the E and W sides of the Kamoamoa delta. The Pu`u `O`o lava pond was very active during this period, fluctuating between 75 and 79 m below the rim.
Eruption tremor along the East rift zone continued with tremor amplitude 2-3x background levels during this period. Microearthquake counts were low beneath the summit and slightly above average along the East rift zone. Seismicity associated with ocean front bench collapse/explosion was recorded at 0939 on 17 April across almost the entire network, with P-arrivals that appeared to have very long-period characteristics. Many smaller events were recorded locally by the Wahaula seismograph (~4 km NE).
A number of collapse events with slightly higher frequency characteristics, including six that were locatable, were detected between 2143 and 2158 on 19 April by the Wahaula station. Based on field evidence and tourist reports, a major bench collapse during that time period was followed by a steam explosion as sea water inundated newly exposed hot rocks (figure 90). One person disappeared into the ocean, and 22 others were treated for injuries caused by the explosion showering them with incandescent lithic blocks and from falls on older flows while fleeing the area. The collapsed bench measured 210 m parallel to the coast, 14 m wide, and 8 m maximum thickness. Ejecta from the steam explosion were directed NW. Blocks near the viewing area and trail were generally <25 cm in size; meter-sized blocks were restricted to within 20 m of the entry area. Blocks were observed up to 200 m from the coast.
|Figure 90. Map of the Lae Apuki ocean entry area following the bench collapse and steam explosion on 19 April 1993. Courtesy of HVO.|
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: T. Mattox and P. Okubo, HVO.