Volcano Watch — Lava taking Hawaiian village, nearing arch

The eruption near Pu`u `O`o on Kīlauea's East Rift Zone continues, with lava entering the ocean both east and west of Kamoamoa and at Lae`apuki. The flows are fed from two vents near Pu`u `O`o, then combine in a single tube system that carries the lava nearly to the coast. The flows entering the sea around Kamoamoa are carried within tubes all the way to the ocean entries. The flow at Lae`apuki continues to have many surface breakouts, and the ocean entries are distributed across the entire flow. 

On Thursday, the Lae`apuki flow had spread along the coast within about 50 feet of the large sea arch, and most of the ancient Hawaiian village had been covered. The National Park Service has marked trails to the coast and onto the new flows so that visitors may see the active lava.

For several weeks, we have been seeing changes around the vent areas on the south and west flanks of Pu`u `O`o. The entire area around the episode 51, 52, and 53 vents has become extremely unstable. As early as February 23, the episode 51 vent structure, a small spatter cone, collapsed to form a hole about 30-50 feet across. A few days later, we discovered that wet rock dust had coated the entire area including one of our instrument cases. This rock-dust deposit apparently formed from a collapse in the area of the episode 51 vent. On February 26, the collapse at the episode 51 vent enlarged to about 80 feet in diameter. On March 13, about half of the episode 53 spatter cone collapsed. A few days later, on March 18, lava from the episode 53 vent partially filled a collapse pit in the area of the episode 52 vents that had formed several months ago.

On March 19, an explosive eruption from within the collapse pit at the episode 51 vent threw fist-sized rock fragments at least 100 feet high and blanketed the surface around the pit with angular rock fragments. This eruptive event was apparently a small phreatic (steam) explosion similar to one that I described in a recent column that killed nine people at Galeras Volcano in Colombia. Another similar eruption killed two additional volcanologists at Guaga Pichincha Volcano in Ecuador on March 12. Had anyone been within a hundred feet of the episode 51 pit, that person also might have been killed by the ballistic rocks ejected from the pit. We have also been mapping a deposit of even larger (up to more than a foot across) angular rock fragments that were ejected from within Pu`u `O`o slightly more than one year ago. These blocks were also emplaced during a phreatic explosive eruption.
By March 21, the bottom of the collapse pit upslope of the episode 51 vent had glowing cracks visible from the air. We observed some new surface cracks between the episode 52 and 53 vents on March 25. We anticipate that this area will collapse at some time in the future. On March 30, another new collapse pit formed high upslope from the episode 51 vents on the Pu`u `O`o cone. This pit is about 65 feet in diameter and apparently has active lava at its base, since there is a dull glow from the pit. On April 1, the remainder of the episode 53 spatter cone collapsed, leaving a crater about 30 by 50 feet.

This long sequence of collapse events near the episode 51, 52, and 53 vents poses a severe hazard in this area, as the collapses apparently occur without warning. The occurrence of a small phreatic explosion from one of the pits adds to the hazard in the area. Several of the collapse pits are located entirely within loose cinder on the flanks of the Pu`u `O`o cone, yet have active lava at the bottom of the pits. Approaching these pits on the ground is very dangerous as the loose cinder can cave in, thereby dumping the unwary observer into a pit. We recommend that hikers avoid the entire area around the Pu`u `O`o cone and, instead, view the lava down at the coastal entries.