Volcano Watch — Kīlauea's episode 51 finally calls it quits

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After being in continuous eruption since Sunday, June 21, the episode 51 vents adjacent to Pu`u `O`o on the East Rift Zone of Kīlauea Volcano finally shut off in the morning on Thursday. Until this extended eruptive period, episode 51 has been characterized by intermittent activity since it began on March 7.

A low lava shield, surmounted by a perched lava pond, has formed just uprift from Pu`u `O`o and is centered on the eruptive vents active during episodes 50 and 51. Earlier flows from the episode 51 vents had been confined to the flanks of this new shield until the past two weeks, when pahoehoe flows advanced to the south beyond the older flows produced during the Pu`u `O`o high-fountain episodes and during episodes 50 and 51. By the time the eruption shut off on Thursday morning, the flows had extended more than three miles from the vents to about the 1,100-foot elevation. The flows began cascading over the steep pali on Monday morning and are located about halfway between the two westernmost `a`a flows erupted from Pu`u `O`o. Last week we predicted that the flows would reach the pali over the weekend, but they did not advance that far until Monday morning.

The flows that poured over the pali between Monday and Thursday were visible from the Chain of Craters Road near Kamoamoa in Hawai`i Volcanoes National Park. No homes or other structures were threatened by this flow, although several important archaeological sites escaped inundation by lava only because the eruption shut off before they were covered.

The lava lake inside Pu`u `O`o remains active at a depth of greater than 230 feet below the rim of the cone. This lava lake produces glow at night and a nearby plume of fume that can be seen from Highway 11, or from the lookout atop Pu`u Huluhulu on the Napau Trail in Hawai`i Volcanoes National Park.

The present pause in activity does not indicate that the eruption, as a whole, is over. We expect that the pond inside Pu`u `O`o will rise over the next few days or weeks, and that the eruption will resume at the same location. It is unclear how much of the lava tube that developed during the just-ended eruptive interval can be reoccupied by lava when the vent starts up again. If lava reoccupies the tube, it will reach the pali much faster than it did the previous time, and archaeological sites and eventually the coastal zone near Kamoamoa could again be threatened. If the tubes are blocked, as they commonly are after brief pauses during eruptions, a new tube system will have to develop and will slow the advance of flows.