Report on Kilauea (United States) — 30 July-5 August 2008
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 30 July-5 August 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, 30 July-5 August 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 30 July-5 August lava flowed SE through a lava tube system from underneath Kilauea's Thanksgiving Eve Breakout (TEB) and rootless shield complex to the Waikupanaha ocean entry. Explosions from the ocean entry were noted on 30 July. On 31 July, about 2.3 acres (or 25 percent) of the bench E of the ocean entry collapsed. A small lava pond at the top of one of the rootless shields was observed during an overflight. The sulfur dioxide emission rate at Pu'u 'O'o was 1,800 tonnes per day on 31 July; the average background rate is about 2,000 tonnes per day.
During the reporting period, Kilauea earthquakes were variously located beneath Halema'uma'u crater, along the Koa'e fault system, N of the summit, along the S-flank faults, and along the E and SW rift zones. Beneath Halema'uma'u crater, 40 or fewer small earthquakes per day also occurred but were too small to be located more precisely.
The vent in Halema'uma'u crater continued to produce a mainly white plume with minor ash content that drifted SW, then occasionally rotated SE. During 1-3 August, seismic signals resembling those from explosions were accompanied an increase in plume vigor and by the color turning temporarily brown. An event on 1 August started with a collapse of a small portion of the vent rim and was followed by ejected incandescent tephra. Night-time incandescence was seen at the base of the plume. Rushing and rock-clattering sounds were heard in the vicinity of the crater. The sulfur dioxide emission rate was high at 800 and 700 tonnes per day, on 31 July and 4 August, respectively. The pre-2008 background rate was 150-200 tonnes per day.
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.