"For the first time since October 1984, Kīlauea did not erupt during a calendar month. Mapping of episode 32 (21-22 April) eruptive products was completed in May and showed that 16.1 x 10⁶ m³ of lava and 0.25 x 10⁶ m³ of tephra (dense rock equivalent) were produced. Lava from the 1983-85 eruption covered 40 km² of the middle E rift zone.

"Following episode 32, magma was first visible in the conduit on 9 May, at approximately 50 m depth. By the end of May, the magma column had risen to within 30 m of the Pu`u `O`o crater floor and remained mostly crusted over.

Deformation. "The summit of Kīlauea continued to inflate during May. However, a period of significant summit subsidence occurred from 22 May at 1800 to 27 May at 0900. During this interval, the Uwekahuna tiltmeter recorded 2.8 µrad of summit deflation. The net inflation during May was 5.7 µrad.

Seismicity. "Harmonic tremor continued at a fluctuating low level in the middle E rift zone near Pu`u `O`o following episode 32. The number of shallow microearthquakes in the E rift zone and summit region varied from several tens to a few hundreds per day. Short-period summit earthquakes increased gradually in response to the slow rate of inflation. Frequent bursts of long-period events and harmonic tremor were recorded from intermediate to deep sources beneath Kīlauea."

Addendum: Episode 33 of the middle E rift zone eruption occurred on 1213 June. Discontinuous low level fountaining and spillover from the Pu`u `O`o vent began at 0430 on the 12th. By 2306, fountaining had become vigorous and continuous. Lava flowed about 3.5 km to the SE over older lavas from Pu`u `O`o before the episode ended at [0453] on the 13th.

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, G. Ulrich, R. Hanatani, R. Koyanagi, and R. Okamura, HVO.