Report on Kilauea (United States) — December 2001
Bulletin of the Global Volcanism Network, vol. 26, no. 12 (December 2001)
Managing Editor: Richard Wunderman.
Kilauea (United States) Low-to-moderate tremor, surface lava flows and ocean entry through early 2002
Please cite this report as:
Global Volcanism Program, 2001. Report on Kilauea (United States) (Wunderman, R., ed.). Bulletin of the Global Volcanism Network, 26:12. Smithsonian Institution. https://doi.org/10.5479/si.GVP.BGVN200112-332010.
19.421°N, 155.287°W; summit elev. 1222 m
All times are local (unless otherwise noted)
During September 2001 through at least early 2002, minor seismic events occurred and tremor remained low to moderate at Kilauea's summit and at Pu`u `O`o. Tiltmeters across the volcano showed some deformation, which is normal for Kilauea. A significant tilt event occurred on 9 December, but was not accompanied by unusual seismicity or change in eruptive activity. A survey of vertical and horizontal movement concluded that during 2001 Kilauea's summit continued to subside at a maximum rate of 7cm/year as magma moved from the summit reservoir to the Pu`u `O`o vent; the S flank moved seaward at a maximum rate of 7cm/year. Lava broke out of the tube system and continued to flow down the Paluma Pali slope, resulting in bench growth at the new Kamoamoa ocean entry.
Geophysical activity. Small deflation events occurred at Kilauea's summit on 12, 13, and 28 September, a large decrease followed by tremor on 17 October. By 21 October tremor at Pu`u `O`o became rather continuous; however, short bursts of higher amplitude tremor returned by 24 October. During 1-8 November weak, long-period earthquakes occurred frequently at the summit. On 8 December rapid deflation (~2.4 µrad) took place at Kilauea's summit, followed shortly thereafter by deflation (~1.9 µrad) at Pu`u `O`o cone. On 9 December abrupt inflation (6 µrad) at Kilauea's summit was followed by much weaker inflation at Pu`u `O`o. Strong earthquakes and tremor accompanied the inflation. A shallow M 3.4 earthquake was registered beneath the SE corner of the caldera. The end of summit inflation and beginning of deflation were notably abrupt. By 10 December, seismicity had returned to normal levels at the summit and tremor at Pu`u `O`o remained moderate.
On 1 January during 1200-2300, deflation occurred at Kilauea's summit (~2.3 µrad), followed shortly thereafter by deflation (~2.5 µrad) at Pu`u `O`o cone. On 3 January during 1210-1950, inflation (~1.6 µrad) was again recorded at Kilauea's summit. A small deflation followed on 11 January.
Through mid-January numerous small, long-period earthquakes with bursts of tremor registered at Kilauea's summit and tilt across the volcano showed no significant deformation.
Lava flow. On 6 September a surface lava flow broke out in the E part of the flow field at an elevation of ~ 600 m on the Pulama Pali slope. The lava followed the route of the E tube from the top to the base of the slope, across the coastal flat and into the ocean at the E Kupapa`u ocean entry. On 13 September two surface flows were active along the W tube system of the Pulama Pali slope. During 28-29 September, a lava flow located W of the active flow field began to enter the ocean at a new area S of an old Kamoamoa camping area. The new W flow developed a tube system by 30 September that could reroute lava from East Kupapa'u to the Kamoamoa entry.
Throughout October lava broke out of the Kamoamoa tube system and flowed on the surface along the entire Puluma Pali slope. Flows increased along the main tube and E Kupapa'u. Around 13 November the Kamoamoa flow was confined to the tube system with at least five points of sea entry. Through the end of November, lava was mostly confined to the tube systems with a few surface flows that broke out of the tubes and produced patches of incandescence.
During December, surface flows and breakouts occurred along all tube systems from just below Pu`u `O`o to the coast. On 10 December, major breakouts were in progress just below Pu`u `O`o. On 18 December two parallel flows moved down Pulama Pali, both along the track of the Kamoamoa tube. The flows, which were sluggish and more than half crusted over, broke out from the tube in the upper half of the slope and descended to the lower third before becoming entirely crusted over. On 20 December a 3-m tall hornito formed at an elevation of ~700 m from a break in the roof of the main lava tube (figure 153).
|Figure 153. On 20 December at Kilauea a 3-m tall hornito formed at an elevation of ~ 700 m from a break in the roof of the main lava tube. Incandescence was observed at the base of the hornito. Courtesy HVO.|
During early January 2002, surface lava flows were visible on Pulama Pali coming from the Kamoamoa lava tube system. A surface flow reached 1.5-2 km down the upper portion of the flow field above the Pulama Pali slope.
Ocean entry. Through most of September lava generally continued to flow down the Pulama Pali slope, across the coastal flat, and into the ocean at the E Kupapa'u ocean entry. The ocean entry tube and the W tube carried lava that broke out on the coastal flat, and the E Kupapa'u bench remained active. Field mapping on 18 September revealed that the relatively larger W flow was within ~ 625 m of the coastline about 1.8 km W of the entry location at East Kupapa`u. Lava flows located W of the active flow field began to enter the ocean at a new area on 28-29 September. By 30 September a new lava bench and an adjacent black sand beach began to form. The new entry, fed by the W flow, was located 500-600 m seaward of the old site of Kamoamoa, 3.7 km from Chain of Craters road.
By 2 October the Kamoamoa bench had widened ten's of meters. The E bench was no longer active and showed signs of rapid erosion under heavy surf. The W bench extended 70 m farther W, reaching a length of about 190 m parallel to the shoreline and extending 60-70 m out from the old sea cliff. The feeding tube, called the Kamoamoa tube, remained small, with supply estimated to be about 15% of the total flux coming from Pu`u `O`o. By mid-October, lava continued to enter the ocean at both E Kupapa'u entries.
On 14 October surf erosion was gradually claiming the eastern part of the bench. Several small-to-moderate littoral explosions were observed at the point where lava entered the sea. By 28 October activity had decreased at the Kamoamoa entry and its bench reached 120 m from the old sea cliff. Surface flow had ended and all lava reached the bench through tubes. On 31 October a new entry point was observed roughly midway between E Kupapa'u and Kamoamoa.
Lava continued to flow into the sea at the Kamoamoa, Kupapa'u, and E Kupapa'u entries through November and December. By 18 November the Kupapa'u entry was inactive, and by 5 December much of the Kupapa'u bench had fallen into the ocean. By 20 December, the Kamoamoa bench was 360 m long, 130 m wide, and was littered with blocks and black sand.
During early January 2002, lava flowed into the ocean at the Kamoamoa entry from multiple locations, mostly at the tip of the bench and especially in the western third or quarter of the bench. The amount of lava entering the ocean at the E Kupapa'u entry was very small.
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.
Information Contacts: Hawaiian Volcano Observatory (HVO), U.S. Geological Survey, PO Box 51, Hawaii National Park, HI 96718, USA (URL: https://volcanoes.usgs.gov/observatories/hvo/).