The eruption along the East Rift Zone continued in June and July after a pause from 30 May to 4 June (BGVN 21:05). On the morning of 4 June, lava began to fill a large collapse-pit over the tube near the base of Pu`u `O`o. Soon thereafter, a breakout at 690 m elevation fed a broad, slow-moving pahoehoe sheet flow. By the late afternoon of 4 June, channelized aa flows were streaming down the face of Pulama Pali (a fault scarp) from breakouts and large pahoehoe sheet flows were emanating from the tube near the base of the pali. Surface flows continued to spread W across the coastal plain below Paliuli. On the morning of 6 June, the flow front reached the ocean near Lae`apuki. By 13 June, three additional ocean entries were established spanning 1.6 km of coastline. All four entries remained active through 14 June, and surface flows diminished to a few breakouts on the coastal plain. After rising to 58 m below the rim on 4 June, the pond in Pu`u `O`o receded to a depth of 80 m.

During 18 June-1 July, tubes delivered lava to the ocean at three points (West Lae`apuki, Lae`apuki, and Kamoamoa) along a 1.8-km stretch of coastline within Hawaii Volcanoes National Park. Just before midnight on 22 June, a large collapse at the Lae`apuki entry removed roughly 12,000 m<sup>2</sup> of the bench and the area immediately inland. Surface flow activity was concentrated on the coastal plain inland of the entry points. A few breakouts were intermittently active on the slope of Pulama Pali. The lava pond at the bottom of Pu`u `O`o Crater remained active at ~85 m below the rim.

Throughout July lava flowed to the ocean through an 11-km-long tube system. Approximately 95% of lava that reached the ocean entered at Lae`apuki; the remaining 5% entered from a 200-m-wide zone of surface flows at West Lae`apuki. At the main Lae`apuki bench, two skylights appeared over the tube within 150 m of the shoreline.

A small collapse of the West Lae`apuki bench was witnessed at 1920 on 10 July. A major collapse at the main Lae`apuki bench claimed several acres at 2000 on 12 July. Both bench collapses were accompanied by explosions and spattering at the shoreline. The Lae`apuki bench was completely rebuilt by 25 July. Explosive activity at this ocean entry was common during the week of 21-28 July, and by 27 July a littoral cone had been constructed. However, the entire Lae`apuki bench collapsed into the ocean again on the evening of 28 July.

Surface flows during the first half of the month were confined to the coastal plain in the center of the Kamoamoa flow field. Later in the month surface flows on the coastal plain occurred within 150 m of the ocean at West Lae`apuki. These flows came within several meters of the kipuka and remnant of the old coastal road at Highcastle and covered 25% of the black sand beach below the Highcastle overlook. Two surface flows occurred at higher elevations. On 23-25 July, a pahoehoe flow from a skylight traveled 300 m down the face of Pulama Pali. In addition, a 300-m-wide lava flow issued from the skylight at 690 m elevation between 26 and 29 July.

Inside Pu`u `O`o, gas pistoning in two distinct lava ponds was observed over several hours on 9 July. The pond levels rose and fell by 15 m during 10-minute cycles. However, the level of the lava pond generally remained at 80-85 m below the rim during most of June and July.

Seismicity. Eruption tremors continued along the East Rift Zone of Kīlauea with amplitudes fluctuating between background and 2-3x background levels in June and July. Microearthquake counts were low to moderate beneath the summit and rift zones. There were several episodes of weak to strong deep tremor from the usual SW source, the strongest of which occurred between 0637 and 0716 on 12 June. Explosive events were detected along the coast of Kalapana between 2330 on 22 June and 0017 on 23 June, at 1900-2300 on 12 July, and at 1700-1900 on 28 July. Several of these events were equivalent to, or greater than, an M 2.8 earthquake. Between 1700 and 1800 on 12 July, a small burst of long-period intermediate-depth events was located beneath the summit.

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 National Park, HI 96718, USA.