Episode 49 (E-49). A line of fissures opened between the East rift zone's Pu`u `O`o and Kupaianaha vents early on 8 November, feeding lava fountains 1-3 m high [through 26 November]. The first fissure opened shortly before 0445 at the base of Pu`u `O`o cone, and others began opening progressively eastward (downrift), with the last developing around 0500 at the base of Kupaianaha shield. The first fissure had stopped erupting by 0930, after producing a small amount of pahoehoe lava. Fountain heights from the remaining en-echelon fissures progressively increased eastward. Fissures immediately uprift of 1123 cone (Pu'u Halulu, built during the first episode of the eruption in January 1983: figure 83) closely followed the line of fissures that formed during E-48 in July 1986 (11:7). That episode broke a pattern of brief, regularly recurring periods of vigorous lava production at Pu`u `O`o and culminated in the building of Kupaianaha shield.

Figure 83. Lava flows (stippled) and eruptive fissures from episode 49 of Kīlauea's East rift zone eruption, as of 8 November at 1600. Courtesy of HVO.

By 1100 on 8 November, fountaining uprift of 1123 cone had subsided to quiet upwelling, feeding pahoehoe lava that advanced SE. Large channelized pahoehoe flows (changing to aa at their distal ends) emerged from the central fissures, near and immediately downrift of 1123 cone, abutting channelized pahoehoe flows from the E fissures. The flow from the easternmost fissure moved N and ponded against the base of Kupaianaha shield by 0950 (figure 83). Other flows from the E fissures moved SE along the edge of the Kupaianaha flow field, reaching ~640 m (2,100 ft) elevation by 1600.

Lava continued to pond near the new vents through the night. By early the next morning, lava from most of the vents had merged into a large channelized aa flow with a terminus near 630 m (2,080 ft) elevation. Only the fissures downrift of 1123 cone were active by the afternoon. Tubes had developed over lava channels near the 1123 fissures, although the frequent spatter activity occasionally ruptured tube roofs and formed small spatter cones near channel heads. Ponded lava covered the eastern fissures.

By 10 November, lava ponded N of the rift began to drain southward, adding to the volume of the flow moving SE. The channel head of the SE-moving flow was nearly 75 m wide, narrowing to ~30 m wide downslope. The flow surged between 1000 on 10 November and 1800 the next day, advancing nearly 4 km and entering the upper portion of the Royal Gardens subdivision. Eastern vent fountains reappeared with the draining of lava that had ponded next to the vents. By the 12th, all activity was confined to a single vent near the E end of the fissure system.

During the next week, the flow widened considerably and channel morphology changed frequently, but the flow front did not advance farther into Royal Gardens. On 18 November, tubes covered the immediate vent area, pahoehoe flowed in the channel to 610 m, then sluggish aa to 550 m. The channel appeared empty the next day, with small aa breakouts emerging from an apparent tube below the crusted channel floor at ~550 m elevation. Two new flows broke out near the vent area that day, but they did not advance far and stagnated within a few days. In the last reports of episode-49 activity, helicopter pilots observed ponded lava and lava moving in a vent-area skylight on 22-25 November, and a sluggish aa flow was seen in the channel on the 26th.

Effects of episode 49 on Pu`u `O`o. The lava pond in Pu`u `O`o crater was ~55 m below the rim between 1 and 4 November. Within a few hours of the onset of E-49 on 8 November, a large dust plume billowed from the crater, and by 0745, helicopter pilots reported that the lava pond had completely drained. At 1025, however, geologists observed an active lava pond ~85 m below the rim of Pu`u `O`o, while the crater floor appeared to remain at its previous level of 46 m below the rim. Rockfalls occurred regularly as the walls confining the pond collapsed. The lava pond seemed to remain active until a series of rockfalls occurred on 11 November, apparently caused by removal of lava and the resulting collapse of the crater floor, leaving a pile of rubble 72-118 m below the rim.

Continued lava production from Kupaianaha vent. Lava originating at Kupaianaha vent has built an extensive flow field since activity began there in July 1986. A well-developed tube system carries Kupaianaha's lava down Kīlauea's S flank toward the sea, with breakouts from tubes feeding surface flows. The small breakouts noted in Royal Gardens subdivision during the first week in November continued for several days after the onset of E-49 fissure activity, but were less frequent. No surface lava from the main (Wahaula) tube was observed on . . . 15-21 November. During that period, the level of lava in a persistent skylight at 655 m (2,150 ft) altitude dropped from ~11 m to ~20 m below the rim. Within the tube, the flow surface had begun to form a crust. Lava continued to move under the crust, but at a reduced rate. On 21 November, a spiny pahoehoe flow broke out of the Wahaula tube at ~550 m (1,820 ft) elevation and advanced ~200 m. Six days later, two new spiny pahoehoe flows emerged from large tumuli on the tube. Geologists speculated that the tube may have been stressed by the E-49 aa flow that passed directly over it downslope at 520 m (1,720 ft) altitude.

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, HVO.