Volcano Watch — Kīlauea lava status; shoreline hazard

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The eruption on Kīlauea's East Rift Zone continued without any pauses this past week. The active flows are confined to the eastern side of the Kamoamoa flow field, and most of the lava is entering the ocean near Kamokuna.

Kīlauea lava status; shoreline hazard...

Map of recent flows from Pu‘u ‘Ō‘ō, August 25 to October 17, 1995.

(Public domain.)

 

The eruption on Kīlauea's East Rift Zone continued without any pauses this past week. The active flows are confined to the eastern side of the Kamoamoa flow field, and most of the lava is entering the ocean near Kamokuna. There were no major changes at Pu'u O'o, where a small lava lake continues to glow in the bottom of the crater. Elsewhere, however, some dramatic changes took place.

The first of these took place before October 13, when several of the skylights in the lava tube collapsed. In particular, skylights at the 2,020- foot and the 2,450-foot elevations became enlarged. By the 17th, the skylight at the 2,450-foot elevation, a mere 23 feet across only a week earlier, had enlarged to become a huge pit nearly 100 feet across. We had some equipment that measured temperature emplaced in this skylight; it abruptly shut off at 2:50 in the morning on October 11, presumably when the first small collapse took place.

A second temperature-measuring device was destroyed when lava welled up and out of the skylight at the 2,245-foot elevation on October 7. This device recorded a spike in temperature, followed by a drop in temperature, then by an increase in temperature before it failed. The probe inserted into the tube was apparently engulfed by lava, which drained away, and was then engulfed as the lava spilled up and out of the skylight.

At the coast, some changes also took place, with a large collapse of a newly formed lava bench between 4:00 p.m. on October 17 and midday on the 18th. The collapse was followed by explosive activity that built a spatter cone at the Kamokuna entry. The section of lava bench that failed was bounded by deep cracks that were first seen on the 14th. These cracks were about 50 feet from the outer edge of the bench.

It has been a long time since we last had a major bench collapse and an equally long time since a new littoral cone was built along the coast. This new cone, about 10 feet tall and 50 feet long, is a half-cone with the outer half missing. Littoral cones have formed repeatedly during the nine years that lava entered the ocean. Most are later buried by younger lava flows or are destroyed as benches collapse into the ocean.

The newly formed bench of lava is unstable because it is built on black sand produced by explosions when lava and seawater mix. In addition, the lava tubes in the benches are commonly aligned parallel to the coast and, as the pressure changes inside the tube, lava in the tube can push the outer part of the bench towards the ocean.

The collapses are extremely hazardous because a chunk of land which appears to be stable can slide into the ocean and because the collapse, which exposes the hot interior of the bench to seawater, can lead to violent explosions that hurl molten lava and incandescent lava blocks hundreds of feet inland. When the bench slides into the water, it also produces a localized tsunami that washes onto the remaining bench. The tsunami consists of seawater heated to nearly the boiling point by hot lava.

In the past, several visitors to Hawaii Volcanoes National Park have been scalded, injured, or killed when they failed to heed the numerous warnings posted in these hazardous areas by the National Park Service. The U.S. Geological Survey's Hawaiian Volcano Observatory advises the National Park Service about the changing hazards posed by the eruption. Lava viewing can be a memorable and enjoyable activity as long as viewers do not enter hazardous and restricted areas.