Volcano Watch — Kīlauea eruption status, March 1995

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The 12-year long eruption along Kīlauea's east rift zone continued without interruption during the past two weeks. The lava erupts from two vents located on the south and west flanks of the Pu'u 'O'o cone. The lava from the west vent travels towards the coast in a well-established underground tube system. The lava from the southern vent flows about one kilometer in its own tube and then drops down into the underlying tube from the western vent. All the lava then travels in a single tube an additional four kilometers to the top of a steep slope called Pulama Pali. Below the break-in-slope at the top of Pulama Pali, the tube system has branched numerous times as the established tube gets blocked, and new surface flows break out, only to develop new tubes. Presently there are two main tubes feeding lava to the coastal plain at Kamoamoa and west of Lae'apuki. Surface flows continue to break out intermittently along the central and western parts of Pulama Pali.

This past week has seen additional changes in the tube system and the rapid advance of a new flow lobe down the center of Pulama Pail, new cascades over the small fault scarp called Paliuli, rapid advance of surface flows along the west side of the flow field, and the formation of a new ocean entry about one kilometer west of Lae'apuki.

The new flow lobe advanced over Paliuli on the western edge of the Lae'apuki flow field on March 23. These beautiful lava cascades quickly crusted over and fed a growing lava pond at the base of the pali to the west of the cascade. By the following day, there were two cascades, and the flow had progressed to the narrow westernmost flow that had advanced over Paliuli in mid-February. Lava accumulated along this inactive flow, and, after several days of ponding, turned and headed for the coast. Large sheet flows covered vegetated areas and buried numerous archeological sites in the Mo'olehua area. The flow reached the road on March 29, crossed the road during the evening, and cascaded into the ocean over the sea cliffs about one kilometer west of the previous end-of-the-road at Lae'apuki.

Heavy steam/hydrochloric acid fume at the ocean entry is combining with black fume from the burning of the asphalt road and smoke from small fires in the vegetated coastal plain. This combined fume is so noxious that the National Park Service has temporarily restricted access to the area by closing the Chain of Craters Road at the Holei Sea Arch turn-around area. The area at the end of the road will continue to be hazardous as long as the recently returned trade winds blow the fumes westward along the coast.

The new flow along the western edge of the flow field is not the only active area. Another tube through the eastern part of the Kamoamoa flow field continues to deliver lava to the coastal plain and feeds two ocean entries. The easternmost ocean entry has been the stronger of the two during the past week. Lava has also cascaded over the central and eastern sections of Paliuli and fed some surface flows in the middle of the flow field which have produced a third intermittently active entry east of the small littoral cone formed last March at Kamoamoa. The estimated volume of lava issuing from the vents and feeding all of these flows continues to be quite high, probably on the order of 500,000 cubic meters per day.

The flows along the western edge of the flow field have covered quite a lot of vegetated ground. As the flows bury vegetation and soil rich in organic material, methane gas is produced. As the methane migrates underground and concentrates in cavities in the old flows, it can explode violently, throwing large rocks into the air. These explosions pose a significant hazard around advancing flows. Only a few weeks ago, a visitor to the National Park and a ranger were injured by one such explosion. The methane can travel underground for 50 to 100 feet before exploding, so lava should be viewed from at least this distance when the flows are covering vegetated areas.

The lava tube system has been changing rapidly during the past few months as the volume of erupted lava has varied. These volume changes cause blockages in the tubes which lead to new surface flows and development of new tubes. If the eruption rate stabilizes, we expect to see the establishment of long-lived tubes, as existed through much of 1994.