Volcano Watch — Eruption takes brief pause, then resumes

The 11-year-long eruption on Kīlauea's East Rift Zone took a brief pause on Thursday, but activity resumed within a matter of hours. 

For the last year, lava has been transported in an underground tube from the two erupting vents on the flanks of Pu‘u ‘O‘o to the ocean near Kamoamoa. The pause in activity was long enough that the tube system drained, and lava stopped flowing into the ocean for several hours Thursday morning. As the eruption restarted, lava reoccupied the tube, produced several surface pahoehoe flows below Paliuli at elevations below several hundred feet, and entered the ocean through the old tube at Kamoamoa at 11:55 a.m.

During, and following, the pause in activity, the summit region has been inflating as more magma enters Kīlauea from below than is erupting. This is in contrast to steady slow deflation of the summit over the last few months, when more lava was erupting than was being supplied from below. The surface flows had slowed by late Thursday afternoon, and the main activity was once again at the coastal entries.

The lava pond inside Pu‘u ‘O‘o has remained at a depth of about 275 feet below the lowest point on the rim. Despite this great depth, a strong glow has been visible at night above the cone. Recently, the bluish volcanic plume has also been strong and has been easily seen from far away due to light Kona wind conditions. There are now two main fume sources at Pu‘u ‘O‘o: one large, diffuse plume from the main cone, and a second, more focused plume from a small collapse pit near one of the erupting vents on the west side of the cone. The two active vent areas have each collapsed, and no lava is visible at the bottom of the pits. There have been a few days when a separate, white, plume of laze from the ocean entries could be seen from Highway 11.

The lava ledges built along the active ocean entries have been very unstable during the last few weeks. Since the collapse on February 7 that we reported several weeks ago, there have been two additional collapses. The first of these took place on February 22 and the second on March 2. The earlier collapse included the entire new lava ledge along with a large spatter cone that had formed on the ledge. Numerous steam explosions were associated with the collapse. Part of the older lava delta also collapsed and slid into the ocean during this event. High lava fountains, coupled with an onshore wind, deposited spatter along the remaining lava delta above the sea cliff.

On March 2, almost the entire ledge formed since February 22 collapsed. Large steam explosions showered the remaining lava delta with incandescent ballistic blocks as large as a foot across. Spatter bombs as large as 2.5 feet across were deposited along the coast for 900 feet and as far inland as 115 feet. Many of the explosions were large enough that we recorded them on seismic instruments as far away as Halema'uma'u. The explosive activity at the coast was still continuing on Friday.

We urge visitors to Hawai‘i Volcanoes National Park who want to watch this activity at the coast to obey the warning signs posted by the National Park Service and to keep a safe distance away. The area is extremely dangerous, and explosions and spattering of widely variable intensity occur without warning, as do collapses of the youngest lava ledge.