Episode 47 (E-47). After 21 days of quiet, intermittent activity resumed at Pu`u `O`o at 1600 on 23 June. For nearly 2 days, spatter and lava spillovers remained within the flat area around the conduit, or moved just over the edge of the spillway. Intermittent fountaining began 25 June at 1400, giving way to sustained fountaining of E-47 at 0419 the next morning. Fountaining ended the same afternoon, and reached maximum heights of 225 m.

During the last 2 hours of activity there were three high fountain jets, ~50 minutes apart, that lasted several seconds . . . . Theodolite measurements of these jets, obtained for the first time, gave maximum heights of 550 m. Intermittent fountaining occurred the last 20 minutes of the episode, ending at 1635.

Three main flows were generated, two extending 2.4 km S and 3.6 km SE mostly over previous lava flows, and one 2.5 km to the N that burned some trees. During E-47, the cone increased 2 m in height, to 257 m above the pre-l983 surface.

Gradual subsidence of the summit commenced at 1000 on 25 June and changed to rapid decline about 0400 the next morning, just before the onset of sustained fountaining. Summit subsidence ended at 1900 with a total loss of 11.1 µrad. By 30 June the summit had regained 5 µrad (figure 43). Sustained high-amplitude tremor started at 0257 on 26 June and ceased at 1614.

Further Reference. Wilson, L., and Head, J., 1988, Nature of local magma storage zones and geometry of conduit systems below basaltic eruption sites: Pu`u `O`o, Kīlauea East Rift, Hawaii, example: JGR, v. 93, p. 14785-14792.

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, and R. Hanatani, HVO.