The . . . eruption continued with lava entering the ocean in the Lae Apuki area . . . . This bench area (W Kamoamoa/Lae Apuki) is defined by a 60-m-wide system of large cracks that extend >300 m from one edge of the delta to the other. After a small bench collapse on 15 June, a surface flow broke out of the active tube where it intersects the crack system. The flow resurfaced much of the bench before stagnating. Small pieces of the bench that fell into the ocean during June were accompanied by littoral explosions that threw incandescent lava as high as 20 m into the air.

On 3 June, a large, channelized aa flow broke out of the tube at 125 m elevation and cascaded over the Pali Uli fault scarp that evening. However, within a day, all of the breakouts from this flow were pahoehoe lava. The flow spread out below the pali and stagnated within a few hundred meters of the shoreline. Another surface flow cascaded over Pali Uli on 9 June, but by 13 June all of the large surface flows had stopped. Except for one small breakout below Pali Uli, no other active lava flows were observed in June.

Surface flows originating earlier in the year from the base of Pulama Pali had built a low, broad shield near 135 m elevation. A number of skylights have since formed on top of the shield, allowing intermittent observations of active lava through the skylights. There was very little change in the active vent area in June, but the Pu`u `O`o lava pond remained active with the surface 77-88 m below the N spillway rim.

Irregular intervals of banded eruption tremor in late April and early May alternated between background level and up to 4x background. Throughout most of May and into early June, however, tremor amplitudes were relatively steady at 2-3x background. Shallow, long-period earthquakes were slightly above average in number, and intermediate-depth long-period events fluctuated between high and low counts. These intermediate-depth events totaled several hundred on 15-17 May, nearly 200 during 22-23 May, and >200 on 29-30 May. More than 100 shallow long-period microearthquakes were also recorded on 30 May. Short-period microearthquake activity was low beneath the summit and along the rift zones. The steady, high levels of tremor recorded in April and May persisted until 11 June, when amplitudes gradually began to decrease to background level. Low-level tremor, alternating with several minutes to several hours of high-amplitude tremor bursts, in somewhat banded patterns, continued through at least 20 June.

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: T. Mattox and P. Okubo, HVO.