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Report on Kilauea (United States) — February 2016


Kilauea

Bulletin of the Global Volcanism Network, vol. 41, no. 2 (February 2016)
Managing Editor: Edward Venzke. Edited by A. Elizabeth Crafford.

Kilauea (United States) Breakouts continue from the June 27th lava flow; new incandescent vent opens on the flank of Pu'u 'O'o cone.

Please cite this report as:

Global Volcanism Program, 2016. Report on Kilauea (United States) (Crafford, A.E., and Venzke, E., eds.). Bulletin of the Global Volcanism Network, 41:2. Smithsonian Institution. https://doi.org/10.5479/si.GVP.BGVN201602-332010



Kilauea

United States

19.421°N, 155.287°W; summit elev. 1222 m

All times are local (unless otherwise noted)


The lava lake in the Overlook vent of Kīlauea, on the floor of Halema'uma'u crater, rose and fell in its regular pattern during July through December 2015, with a few episodes of spattering around the lake. East Rift Zone (ERZ) lava flows continued N and E of Pu'u 'O'o with new tube branches developing. Small lava flows continued within the Pu'u 'O'o crater, and a new incandescent vent appeared on the NE side of the cone in December. Seismicity was generally higher than normal in the Southwest Rift Zone and lower than average at the summit and in the East Rift Zone. SO2 emissions rates were varied but continued a long term decline. Information for this report is from the U.S. Geological Survey Hawaiian Volcano Observatory (HVO) quarterly reports.

Activity at Halema'uma'u. The lava lake at Halema'uma'u Crater was much less active since its overflow onto the crater floor on 28 April 2015. The only disruptions to the normal N-S circulation pattern were short-lived episodes of spattering around the lava lake edges which created local zones of downwelling, and some wall collapses. The lava surface rose and fell numerous times during DI (Deflation-Inflation) events associated with changes in summit pressure. The highest level the lake reached was 34.5 m below the crater rim in late December, and the lowest level was 84.5 m below the rim in mid-October. Thermal cracking sounds were common during high levels, and collapses of juvenile veneer from the vent walls were common during drops in level. An ashy plume was reported on 1 July 2015 when part of the rim and wall of the Overlook crater collapsed into the lake, causing a small explosion with intense spattering. A very-long-period earthquake at the summit on 24 November corresponded to the collapse of a large section of the N rim and wall of the summit vent. This caused increased lake spattering and turbulence.

Activity in the East Rift Zone (ERZ). Lava flows remained active in the ERZ from July through December 2015. During July-September three major branches of lava flowed N, NE, and E from Pu'u Kahauale'a. The N and NE branches were fed by a new tube branch. In addition small sporadic breakouts at the base of Pu?u ?O?o occurred during July and August (figure 252). The N and NE branches stopped advancing by October. Most activity shifted to the N and W sides of the flow field in late November from a new tube branch located about 300 m downslope from the June 27th fissure C vent (figure 253). Smaller breakouts along the S and E margin of the June 27th flow were also active into November.

Figure (see Caption) Figure 252. Flow field changes in the ERZ of Kīlauea between 30 June and 30 September 2015. Three active branches N and E of Kahauale'a added the most lava, fed from a new tube branch. Sporadic, smaller breakouts closer to Pu'u 'O'o occurred during July and August. Courtesy of HVO.
Figure (see Caption) Figure 253. Flow field changes in the ERZ of Kīlauea between 30 September 2015 and 5 January 2016. The flow fields moved to the N and W of the June 27th flow field during the last quarter of 2015 with flows coming from a new tube branch which developed closer to the main fissure at Pu?u ?O?o. Smaller breakouts on the E side of the flow ended by the end of November. Courtesy HVO.

Activity at Pu'u 'O'o. A number of small flows erupted from the three main incandescent vents within the crater during this period (figure 254). During 27-28 August 2015, coincident with the breakout from the upper tube on the ERZ (figure 252), a larger flow from the NE pit resurfaced the entire crater floor. Significant flows on 24 and 25 November from two of the pits were also confined to the crater floor. The small lava pond that formed in the W pit in April 2015 was still present. The pond surface was about 20 m below the pit rim. Stronger than usual fumes from the W wall of the north pit hindered access to the W pit by researchers. Sometime between 3 and 8 December, a new incandescent vent opened on the NE flank of the Pu'u 'O'o cone (figure 255).

Figure (see Caption) Figure 254. Oblique aerial photograph of Kīlauea showing crater and pits of Pu'u 'O'o. Red circles mark the approximate location of vents that erupted lava between July and December 2015. Courtesy of HVO.
Figure (see Caption) Figure 255. Photo of Kīlauea looking SW at Pu'u 'O'o on 17 December 2015, showing a new incandescent vent on the NE flank of cone. Courtesy of HVO; photo by T. Orr.

Seismicity. Seismicity between July and December 2015 was higher than normal in the Southwest Rift Zone, and relatively low in the summit and the ERZ areas. There were two notable periods of increased activity; for a few days in October following a slow-earthquake tectonic event where the S flank slipped about 3 cm southeastward, and during a period of a high lava stand in the summit in late December. The largest earthquake during this time was a M 3.9 event that occurred under Kīlauea's S flank.

Within the Southwest Rift Zone (SRZ), seismicity was focused at shallow depths (0-5 km) at the SW end of the rift; it generally occurred in clusters of several days of activity with little to no activity between those times. The seismic activity in the SRZ is interpreted by HVO seismologists to be tied to the transport of magma and volatiles into the zone. For three days in October, seismicity was also elevated in the deep mantle source area below the distal end of the SRZ.

Summit seismic activity was characterized by the typical cycles of tremor and non-tremor, associated with spattering in the overlook vent, and composite events at least a few times per month where rock-falls from the crater walls of the overlook vent generated very-long-period earthquakes in the conduit. An interesting swarm of earthquakes, at a rate of over one per minute at its peak, occurred in the Kīlauea caldera on 31 October 2015 between about 1830 and 2215 UTC; a burst of tremor interrupted the swarm from 2110 to 2123. At least 120 individual events, many were long-period earthquakes, were detectable on the summit spectrogram. The swarm occurred during a period of deflationary tilt, and tremor returned following the swarm. This swarm in the caldera occurred two days after the elevated seismicity in the deep mantle source area, and 15 days after the slow earthquake.

SO2 emission rates. Sulfur dioxide emission rates have been measured by multiple methods over time. The sulfur dioxide correlation spectrometer, or COSPEC, and differential optical absorption spectroscopy (DOAS), are two of these methods. Different digital processing techniques developed over time for the data also aid researchers in understanding the changes observed in SO2 values. Figure 256 shows Kīlauea summit SO2 emissions as recorded and processed by different methods since 2008. While the absolute values vary, the downward trend in SO2 emissions since the Halema'uma'u crater vent opened in 2008 is clear. To gather summit emissions data, the COSPEC instrument is driven at a constant speed around Kīlauea caldera on Crater Rim Drive, and the instrument records the total amount of SO2 overhead.

Figure (see Caption) Figure 256. Daily average summit SO2 emissions in tons per day at Kīlauea since 2008, as measured and processed by different methods. Black squares represent measurements from road-based traverse campaigns, using the single fit 305-315 nm window (SFW) processing technique with the COSPEC instrument. Blue squares represent the same data processed with a dual fit window (DFW) technique, and the pink triangles represent SRT-modeled values. HVO discontinued reprocessing data using the SRT-DOAS model at the end of 2014. Vertical bars represent the standard deviation of individual measurement values recorded on a single day. Image courtesy of HVO.

Values for SO2 emissions from the ERZ and Pu'u 'O'o are collected by taking a similar set of measurements down the Chain of Craters road. Data from 2014 and 2015 (figure 257) show the dramatic spike in emissions at the beginning of the June 27th 2014 breakout followed by gradual decline. A steady increase in emission rate was recorded from the beginning of 2015 until early May, when a sharp decline began coincident with the magma intrusion into the S caldera. The second half of 2015 is characterized by fairly low, relatively consistent emissions, with some notable outliers.

Figure (see Caption) Figure 257. 2014 and 2015 daily average SO2 emissions in tons per day for the East Rift Zone (ERZ), as measured along Chain of Craters Road under trade-wind conditions, with standard deviations of all traverses on a single day. Image courtesy of HVO.

Geological Summary. Kilauea overlaps the E flank of the massive Mauna Loa shield volcano in the island of Hawaii. Eruptions are prominent in Polynesian legends; written documentation since 1820 records frequent summit and flank lava flow eruptions interspersed with periods of long-term lava lake activity at Halemaumau crater in the summit caldera until 1924. The 3 x 5 km caldera was formed in several stages about 1,500 years ago and during the 18th century; eruptions have also originated from the lengthy East and Southwest rift zones, which extend to the ocean in both directions. About 90% of the surface of the basaltic shield volcano is formed of lava flows less than about 1,100 years old; 70% of the surface is younger than 600 years. The long-term eruption from the East rift zone between 1983 and 2018 produced lava flows covering more than 100 km2, destroyed hundreds of houses, and added new coastline.

Information Contacts: Hawaiian Volcano Observatory (HVO), U.S. Geological Survey, PO Box 51, Hawai`i National Park, HI 96718, USA (URL: https://volcanoes.usgs.gov/observatories/hvo/)