Volcano Watch — Ten-year lava flow from Kīlauea's episode 51 continues

The 10-year long eruption of Kīlauea Volcano continues from the episode 51 vents located on the west flank of the Pu`u `O`o cone. The flows advanced slowly from October 3 until October 28, when they began to flow over the pali above Kamoamoa.

By Wednesday afternoon, this `a`a flow had advanced rapidly to roughly the 1,000-foot level. By Friday morning, the flow had advanced only a little more, to the 900-foot level, but was getting wider as the lavaspread out. These new flows are located west of the westernmost `a`a flow erupted in 1986 from the Pu`u `O`o cone. The last flows to advance this far moved down the pali to the east of the 1986 `a`a flow to the 1,000-foot level in late July. These active flows are clearly visible from the Chain of Craters Road near Kamoamoa inside Hawai`i Volcanoes National Park.

The earthquake that preceded the start of the episode 52 eruption on October 2 has apparently changed the plumbing beneath Pu`u `O`o. Before the earthquake occurred, the lava pond inside Pu`u `O`o had been at high levels, perhaps 125 feet below the rim of the cone, during eruptive intervals and around 250 feet below the rim, during pauses in the eruption. Soon after the start of episode 52, and the slightly later start-up of the episode 51 vents, the pond has remained deep, around 250 feet below the rim, yet the eruption at the episode 51 vents continues.

In addition, the level of activity inside the Pu`u `O`o pond has been higher than previously seen. These high levels of activity apparently cause the extremely strong harmonic tremor (ground variation) that we have recorded periodically on our seismic stations during the last week and a half. The lava has been streaming across the pond surface from the north side toward the east side, where it cascades 40 to 50 feet back into a deeper level in the cone.

The episode 51 vents have been the site of intense degassing in the last month, but no glow or spatter has been observed there since late September. The lava from the episode 51 vents is being fed downslope through tubes above the 2,100-foot elevation. Below that point, there are small pahoehoe flows above the pali, but most of the lava is flowing down the steep pali as a channelized `a`a flow. At times these flows stagnate and solidify, and at other times, the incandescent `a`a surges downslope.

Most of the eruptive intervals since last February have lasted one to two weeks. These active periods were separated by inactive periods. After each inactive period, the lava reoccupies only a small part of the lava tubesystem, so the flows pond near the vent. With longer eruptive periods, the tube system develops, and lava can flow far from the vents, eventually reaching the pali, or beyond. The longest occurred from June 21 to July 23 for a total of 32 days. The current eruptive interval started on October 2, so has already been active for 27 days. If we use past behavior to predict the future, then it seems likely that this eruptive interval will stop within a few days before the flows advance across the coastal plain to the Chain of Craters Road and the ocean beyond. However, the October 2 earthquake changed the volcanic system, and the maximum duration of past active periods may no longer be applicable. If this eruption continues longer than any previous active periods, the flows will slowly advance towards the ocean near Lae`apuki, just west of Kamoamoa.