Report on Kilauea (United States) — 17 September-23 September 2008
Smithsonian / US Geological Survey Weekly Volcanic Activity Report,
17 September-23 September 2008
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2008. Report on Kilauea (United States). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 17 September-23 September 2008. Smithsonian Institution and US Geological Survey.
19.421°N, 155.287°W; summit elev. 1222 m
All times are local (unless otherwise noted)
HVO reported that during 17-23 September, lava flowed SE through a tube system from underneath Kilauea's Thanksgiving Eve Breakout (TEB) and rootless shield complex, reaching the Waikupanaha ocean entry. During 18-19 September, explosions from the base of the plume ejected debris into the air. The sulfur dioxide emission rate at Pu'u 'O'o was 1,700 tonnes per day on 21 September, near the background rate as averaged over the past 25 years.
During the reporting period, Kilauea earthquakes were variously located beneath and to the S of the caldera, and along the S-flank faults. Beneath Halema'uma'u crater, 40-80 small earthquakes per day (background is 20-40) also occurred but were too small to be located more precisely. On 19 September a M 4.3 earthquake, felt island-wide, was located at a depth of 9.7 km below the S flank. The vent in Halema'uma'u crater continued to produce a predominantly white plume with occasional minor ash content that drifted mainly SW. Weak night-time incandescence was intermittently seen at the base of the plume, and rock impact and rushing gas sounds were heard in the vicinity of the crater. The sulfur dioxide emission rate was 1,200 tonnes per day on 21 September. The pre-2008 background rate was 150-200 tonnes per day.
Geological Summary. 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.