EPISODE 28

"Episode 28 began at 1905 on 3 December. High fountaining and continuous lava production lasted for 14.5 hours, ending at 0941 on 4 December. The lava spilled over the broad NE rim of the cone (Pu'u O) and produced a broad short aa fan to the NE and two larger aa flows to the SE. The SE flows extended 4.7 km from the vent, ending about 1.2 km short of Royal Gardens subdivision. The high fountains were accompanied by heavy tephra fallout in a broad swath downwind of the vent. Episode 28 produced 12.3 x 10⁶ m³ of lava and approximately 0.2 x 10⁶ m³ of tephra (lava equivalent).

"Pu'u O was in repose for the remainder of the month. On 30 December, low fountains (3-10 m) produced thin pahoehoe overflows that reached the base of the cone. Similar activity occurred intermittently for the next 4 days until high fountains and continuous lava production signaled the start of episode 29.

Deformation. "Summit subsidence began at about 1900 on 3 December, at the start of episode 28. The Uwekahuna tiltmeter recorded continuous summit deflation until 1330 the next day, resulting in a net tilt change of 15.9 µrad. During the rest of the month the summit tilt recovered 17.7 µrad.

Seismicity. "Harmonic tremor associated with episode 28 at Pu'u O started to increase gradually at 1815 on 3 December. By 1905 tremor recorded at the Kamoamoa seismic station increased to a level characteristic of high lava fountaining. High-amplitude tremor continued for nearly 15 hours. The sharp decrease in tremor following the end of the eruptive episode was recorded at 0941 on 4 December. For the rest of December, tremor was at low levels, varying from the fluctuating amplitude associated with gas-pistoning activity at Pu'u O, to continuous amplitude with no visible lava activity.

Addendum: The current Kīlauea eruption sequence celebrated its 2nd anniversary on 3 January 1985 with the start of episode 29. Fountains up to 460 m high fed aa flows to the NE and SE during the 16 hour episode.

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: C. Heliker, R. Koyanagi, A. Okamura, G. Ulrich, HVO.