Report on Kilauea (United States) — 29 April-5 May 2009
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 29 April-5 May 2009
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2009. Report on Kilauea (United States). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 29 April-5 May 2009. Smithsonian Institution and US Geological Survey.
19.421°N, 155.287°W; summit elev. 1222 m
All times are local (unless otherwise noted)
During 29 April-5 May, HVO reported that lava flowed SE from underneath Kilauea's Thanksgiving Eve Breakout (TEB) and rootless shield complex through a lava tube system, reaching the Waikupanaha and Kupapa'u ocean entries. Some explosions occurred at the Waikupanaha ocean entry. The vent in Halema'uma'u crater continued to produce a white plume that sometimes caused poor air quality in nearby areas. Sounds resembling rushing gas were sometimes heard in the vicinity of the crater. Various amounts of tephra, spatter, and ash were retrieved from collection bins placed near the plume during the reporting period. On 3 May, unusually bright incandescence seen from the vent on the web camera was accompanied by a decrease in summit tremor levels of about 40 percent. During 4-5 May, bright incandescence was again noted; summit tremor levels were variable but never exceeded moderate values.
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.