Report on Kilauea (United States) — 1 July-7 July 2009
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 1 July-7 July 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, 1 July-7 July 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 1-6 July, 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. Thermal anomalies detected in satellite images and visual observations revealed active surface flows on the pali and on the TEB flow field.
A sequence of rockfalls within the cavity on the floor of Halema'uma'u crater began at 1338 on 30 June. The first rockfall was followed by a loud explosion, and produced a M 2.4 equivalent earthquake felt at HVO and the adjacent Jaggar Museum. The gas plume turned brown for several minutes. Several more rockfall signals were detected by the seismic network; two more were felt locally. Booming sounds also accompanied several of the rockfalls. Chunks of the vent rim fell into the cavity. By 1600, more than 30 rim-collapse events had been recorded by seismometers, with a few more occurring on 1 July. Seismic tremor amplitudes decreased by more than 50 percent. By 1800, the levels were at their lowest values since 30 August 2007. On 1 July, scientists observed rocky rubble within the vent and no incandescence. Sporadic gas jetting noises were heard coming from the vent.
During 1-2 July, a few areas of incandescence were seen in the vent by the web camera. During 2-4 July, scientists observed a small ponded lava surface and weak spattering deep within the vent. The sulfur dioxide emission rate at the summit remained elevated; measurements were 360 and 200 tonnes per day on 3 and 5 July, respectively. The 2003-2007 average rate was 140 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.