Activity within the Pu`u `O`o crater was at a diminished level during late October-23 November 1997. Lava in the crater was visible only from the crater walls. The Pu`u `O`o vent rarely effused lava onto the crater floor during November; the magma column remained 10-20 m below the rim. Magma in the vent circulated below the crusted lava surface, where it was not visible except from the air.

Lava from the S shield continued to travel ~10 km to the coast in tubes; travel time was estimated at ~3 hours from the vent to the ocean. The eruption rate was 500,000-600,000 m³/day. Although lava continued to flow into the ocean at East Kamokuna and Waha'ula, no breakouts of lava from the tubes onto the coastal plain occurred after the 18-19 October event (BGVN 22:09).

At East Kamokuna, a bench collapse in the first week of November removed 1.9 hectares of recent deposits and created a new cliff a few meters high and ~50 m long; after the collapse, lava began building a shelf at the foot of the new cliff. Curtain-like steam plumes rose continuously from the 500-m-long edge of the lava flow. A smaller lava bench collapse (0.26 hectares) occurred on 24 November.

Sulfur dioxide emissions from Pu`u `O`o remained high during November. Although during late October the emission rate had been 1,500-2,000 metric tons/day (t/d), during November it increased to 2,800 t/d and occasionally reached 5,000 t/d. On 16 November, eastern Hawaii, especially Hawaii Volcanoes National Park, was engulfed in one of 1997's worst volcanic-smog episodes. Elevated levels of volcanic smog were detected as far away as Oahu (~330 km NW). Gentle winds from the SE pushed SO₂ emissions from Kīlauea's E rift zone inland, resulting in levels of airborne SO₂ that exceeded Environmental Protection Agency standards; the National Park Service thus closed headquarters at the Kīlauea summit for the day. On 7 December, SO₂ emissions were 4,300 t/d.

Although visible activity within Pu`u `O`o crater remained diminished, visitors and nearby residents heard roaring sounds during 24 November-5 December. Tephra fell up to 10 km from the vents and included "Pele's hair" (thin strings of solidified lava ~2.5 cm in length). During 28-30 November, a particularly active period of tephra deposition occurred; the associated emission events were detected on seismic instruments near the Pu`u `O`o vent.

On 7 December the SW flank of Pu`u `O`o cone collapsed, creating a funnel-shaped pit ~50 m in diameter at the surface midway between the S base and rim. A small glowing hole on the floor of the pit revealed that the pit intersected the magma supply system underlying the cone and flank vents. The new collapse pit resembled the Great Pit that formed on the cone's W slope in early 1993 (BGVN 18:02 and 18:03); the Great Pit later enlarged, causing the cone's W wall to collapse in January 1997 (BGVN 22:01). Pits of this type form when Pu`u `O`o is undermined by magma feeding the on-going eruption.

Lava output inside Pu`u `O`o crater visibly increased during 7-8 December; flows from the crater vent filled the crater's E side. The increased activity may have been related to the formation of the new collapse pit.

Kīlauea is one of five coalescing volcanoes that comprise the island of Hawaii. Historically its eruptions originated primarily from the summit caldera or along one of the lengthy E and SW rift zones that extend from the summit caldera to the sea. This latest Kīlauea eruption began in January 1983 along the E rift zone. The eruption's early phases, or episodes, occurred along a portion of the rift zone that extends from Napau Crater on the uprift end to ~8 km E on the downrift end. Activity eventually centered on what was later named Pu`u `O`o. Between January 1983 and December 1996 the volume of erupted lava totaled ~1.45 km³.

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, Hawaii Volcanoes National Park, HI 96718, USA (URL: https://volcanoes.usgs.gov/observatories/hvo/); Ken Rubin and Mike Garcia, Hawaii Center for Volcanology, University of Hawaii, Dept. of Geology & Geophysics, 2525 Correa Rd., Honolulu, HI 96822 USA (URL: http://www.soest.hawaii.edu/GG/hcv.html).