Report on Kilauea (United States) — 3 April-9 April 2002
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 3 April-9 April 2002
Managing Editor: Gari Mayberry
Please cite this report as:
Global Volcanism Program, 2002. Report on Kilauea (United States). In: Mayberry, G (ed.), Weekly Volcanic Activity Report, 3 April-9 April 2002. Smithsonian Institution and US Geological Survey.
19.421°N, 155.287°W; summit elev. 1222 m
All times are local (unless otherwise noted)
During 4-6 April, a remarkable series of deflation and inflation events occurred at Kilauea. Beginning on 4 April around 2100, Kilauea's summit deflated and 30 minutes later Pu`u `O`o followed. The summit deflated ~1.7 microradians and Pu`u` O`o dropped ~9 microradians. On 5 April rapid inflation began at 1600 at the summit and 12-13 minutes later at Pu`u` O`o. Inflation ended at the summit at 1700, when the summit abruptly deflated, and at Pu`u` O`o at 1800. Then, tilt at Pu`u` O`o oscillated three times between rapid deflation and slower inflation. After the tilt temporarily settled down, on 6 April at 0508 another oscillatory period commenced. Following 4.5 oscillations, tilt resumed slow, bumpy inflation after 1200 that same day.
During the period of deflation and inflation, long-period earthquakes increased at the summit, while tremor remained steady at Pu`u` O`o until it slightly increased on 6 April. Small surface lava flows were seen on the lower portion of Pulama pali and the upper part of the lava fan. During a brief trip to Pu`u` O`o on the morning of the 6th, scientists saw that the crater lake had risen ~8 m since 29 March (the lake surface was 17 m below the E rim), several cones were active, and lava was flowing into the lava lake from two vents. By the 7th activity had calmed down; tilt was relatively steady, volcanic tremor at Pu`u` O`o was at moderate levels, and tremor at the summit was at low-to-moderate levels. On the 8th there was activity at the rootless shields. Incandescence was not visible at Pu`u` O`o, which possibly means that lava lake activity was waning or had ended.
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.