USGS Volcano Hazards Program Volcano Update
Recent Observations at Kilauea summit: The summit tiltmeter network recorded very weak inflation. The lava lake level slowly fluctuated and may have risen a small net amount over the past 24 hours. The most recent (preliminary) sulfur dioxide emission rate measurement was 600 tonnes/day on November 20, 2012; this value is at the low end of measurements made between rise/fall events but still constitutes a background level of emissions. Although not measured this morning, a very small amount of ash-sized tephra (including fresh spatter bits and Pele's hair) was probably carried out of the vent in the gas plume and deposited on nearby surfaces.
Seismic tremor levels remained steady at low values. Ten earthquakes were strong enough to be located beneath Kilauea: 3 beneath the area just west of the summit caldera, 1 just south and 1 just east of the summit caldera, 1 deep quake within the upper east rift zone, and 4 on south flank faults. The GPS network recorded neither net extension nor contraction across the summit caldera since November 2.
Background: The summit lava lake is deep within an ~160 m (520 ft) diameter cylindrical vent with nearly vertical sides inset within the east wall and floor of Halema`uma`u Crater. Its level fluctuates from about 40 m to more than 200 m (out of sight) below the floor of Halema`uma`u Crater. The vent has been mostly active since opening with a small explosive event on March 19, 2008. The surface level of the lava lake has again dropped below the inner ledge (~31 m or 100 ft below the floor of Halema`uma`u Crater on October 29, 2012) and has not risen above and flooded the ledge since October 28. The lake level responds to summit tilt changes with the lake receding during deflation and rising during inflation.
Recent Observations at the middle east rift zone vents: Lava flows remained active in two branches on the coastal plain; the eastern branch was observed entering the ocean starting at about 1 pm yesterday by a small group of UHH geologists at a location about 500 m east of the easternmost boundary of Hawai`i Volcanoes National Park; a wispy plume is visible from the ocean entry point this morning in one of the three Webcams with a view of that location suggesting that lava continued to flow into the ocean. The shorter western branch appeared weakly active.
HAZARD ALERT: Lava entering the ocean builds lava deltas. The lava delta and adjacent areas both inland and out to sea are some of the most hazardous areas on the flow field. Frequent delta/bench collapses give little warning, can produce hot rock falls inland and in the adjacent ocean, and can produce damaging local waves. The steam plume produced by lava entering the ocean contains fine lava fragments and an assortment of acid droplets that can be harmful to your health. The rapidly changing conditions near the ocean entry have been responsible for many injuries and a few deaths.
At Pu`u `O`o, a small piece of the rim collapsed in the lava lake on the northeast edge just before midnight and a small lava flow issued from the east source on the south crater floor edge between 9:30 pm last night and 12:30 am this morning. Glow could be seen from the spatter cone on the north edge of the crater floor with weaker glow from both sources in the south part of the floor. The tiltmeter on the north flank of Pu`u `O`o cone recorded weak inflation, with a small offset due to the magnitude-4.3 Lo`ihi earthquake at about 6 pm, before deflation set in around 4:30 am this morning; GPS receivers on opposite sides of the crater recorded neither net extension nor net contraction since late October. Seismic tremor levels near Pu`u `O`o were low and decreasing. The most recent (preliminary) sulfur dioxide emission rate measurement was 300 tonnes/day on November 20, 2012, from all east rift zone sources.
Background: The eruption in Kilauea's middle east rift zone started with a fissure eruption on January 3, 1983, and continued with few interruptions at Pu`u `O`o Cone, or temporarily from vents within a few kilometers to the east or west. A fissure eruption on the upper east flank of Pu`u `O`o Cone on Sept. 21, 2011, drained the lava lakes and fed a lava flow that advanced southeast through the abandoned Royal Gardens subdivision to the ocean within Hawai`i Volcanoes National Park in early December 2011. Since late December 2011, the flows have remained intermittently active on the pali and the coastal plain but have not entered the ocean. In general, activity waxes with inflation and wanes with deflation.
Hazard Summary: East rift vents and flow field - near-vent areas could erupt or collapse without warning with spatter and/or ash being wafted within the gas plume; potentially-lethal concentrations of sulfur dioxide gas may be present within 1 km downwind of vent areas. All recently active lava flows are within Hawai`i Volcanoes National Park, adjacent State land managed by the Department of Land and Natural Resources, and private property within the Royal Gardens subdivision; the lava flows do not pose a hazard to any structures not already within the County-declared mandatory evacuation zone. Kilauea Crater - ash and Pele's hair can be carried several kilometers downwind; potentially-lethal concentrations of sulfur dioxide can be present within 1 km downwind.
Viewing Summary: East rift zone flow field - The active lava flows were within the closed-access Kahauale'a Natural Area Reserve (NAR) and the abandoned Royal Gardens subdivision and can only be viewed from the air. Under favorable weather conditions, these flows can be seen from the County Viewing Area at Kalapana (Lava hotline 961-8093). Pu`u `O`o Cone, the strip of coastal plain nearest the ocean, and Kilauea Crater - these areas are within Hawai`i Volcanoes National Park; Park access and viewing information can be found at http://www.nps.gov/havo/planyourvisit/lava2.htm.
Update in Common Alerting Protocol (CAP) format