Volcano Watch — Flow stops, but eruption goes on

Regular readers of this column may have noticed that the last week's column ended in mid-sentence. This unfortunate situation was caused by an inadvertent mistake in layout. As you may recall, the column was about the magnitude 7.8 earthquake in Japan the week before that and the tsunami watch called and then cancelled for Hawai`i and the rest of the Pacific Basin. The missing conclusion to the column discussed the circumstances that led to so many fatalities in Japan and then outlined appropriate response to large local earthquakes that might generate a tsunami. The text should have ended as follows: "In Japan, particularly for people living on Okushiri Island located nearly at the epicenter, many of the people killed simply did not have - (text from here on was missing) time to get to high ground. Here in Hawai`i, if you are located close to sea level and feel a strong earthquake (one where the shaking continues for more than a minute or so), do not wait to hear the tsunami sirens but instead head for higher ground immediately, as there may be only a few minutes between the earthquake and the ensuing tsunami."

The 10-year long eruption on Kīlauea's East Rift Zone continues without interruption. Because of poor weather conditions, we have been unable to make observations into Pu`u `O`o this past week and have no new information on the level of activity of lava in the pond inside the cone. Early Friday morning, we recorded a series of seismic events at the cone that are probably small collapses of sections of the cone walls. At about the same time, the flow of lava into the ocean stopped, although the eruption continues as seen in seismic tremor recorded at the Pu`u `O`o cone. The rim of the Pu`u `O`o cone and the area near the crusted-over vents on the south and west sides of the cone continue to be unstable and dangerous. Until Friday morning, the flows had continued to flow underground in tubes from two vents, which we call the episode 51 and episode 53 vents, all the way to two ocean entries at Kamoamoa. Because the eruption is continuing, we expect to see more voluminous surface flows inland on the lava delta or along the pali. The main flow may reoccupy the existing tube or build a new tube to the ocean.

Until Friday morning, the ocean entries consisted of a large eastern entry point which built a new lava bench along the coast and a much smaller entry on the western edge of the Kamoamoa lava delta. The new lava bench at the large eastern entry has built up, attaining the same elevation as the main delta, but is separated from it by a large crack that runs parallel to the coast. We anticipate that this bench, like a sequence of previously formed benches in the same location, will slide into the sea at some time.

The likelihood of future collapses in this area is a good reason to obey the posted area closure signs placed by the National Park Service. Many people ignore these closure signs, particularly at night, and place themselves in great danger when they go out on the lava bench adjacent to the ocean. It is difficult to recognize where the older, more stable, delta stops and the young, unstable bench begins, because there is no change in elevation between the delta and the new lava bench and because new flows have buried the crack in many places.

Other hazards exist near the ocean entries, including steam explosions that have thrown incandescent lava blocks as far inland as 500-600 feet, occasional lava spattering events that throw molten blobs of lava hundreds of feet into the air. Depending on the wind speed and direction, these spatter bombs can fall on the lava delta. The fume cloud is a moderately concentrated hydrochloric acid plume that will burn eyes, make holes in clothes, and corrode camera gear.

An additional hazard that is particularly pertinent is steam white-outs on the flow field. Much of the flow field is still beneath the surface and heavy rain quickly penetrates into the flows along cracks where it is heated to steam. During such periods, however brief, this steam creates white-out conditions that can be so severe that you cannot see your own feet. If this happens, stay where you are and enjoy the sauna! Wait until the heavy rain stops, and the steam will abate within a few minutes. You will then be able to see to safely walk across the flows.