Kīlauea eruption update and comparison to 1924 eruption
Author: Nick Lilja
|| Published: 5/15/2018 at 11:38pm
Kīlauea continues to spew lava – and now lava bombs – across parts of Hawaii. The USGS is now warning that a possible explosive eruption is imminent.
The Latest:
As of early this morning, eruption of ash from the Overlook vent within Halemaumau crater at Kilauea Volcano’s summit has generally increased in intensity. Ash has been rising nearly continuously from the vent and drifting downwind to the southwest. Ashfall and vog (volcanic air pollution) has been reported in Pahala, about 18 miles downwind. NWS radar and pilot reports indicate the top of the ash cloud is as high as 10,000 to 12,000 feet above sea level, but this may be expected to vary depending on the vigor of activity and wind conditions.
Radial tilt during the past 48 hours
Ash emission from the Kilauea summit vent will likely be variable with periods of increased and decreased intensity depending on the occurrence of rockfalls into the vent and other changes within the vent.
At any time, activity may become more explosive, increasing the intensity of ash production and producing ballistic projectiles near the vent.
Resource on volcanic ash hazards: https://volcanoes.usgs.gov/volcanic_ash/
Resource on vog: https://vog.ivhhn.org/
– USGS.gov
The USGS On Twitter:
Summary of #HVO#Kilauea VAN/VONA: Ash eruption at summit has increased in intensity. NWS radar & pilot reports show top of the ash cloud is as high as 10,000-12,000 feet above sea level. Ashfall and vog has been reported in Pahala (18 mi downwind). #KilaueaEruptspic.twitter.com/ChzRdu0Ch7
The first explosion, neither seen nor heard, took place during the night of May 9–10 with small rocks reported to have been thrown out of the crater. Larger explosions followed, starting on May 13 and spaced a few hours apart. During the same time, Halemaumau continued to collapse, its failing walls contributing to the debris thrown from the crater. Clouds of rock particles ejected into the air often obscured the crater from view. Toward the end, it became difficult to distinguish the cloud of a small explosion confined to the crater from the dust cloud generated by a rock avalanche; consequently, the end date of the eruption is somewhat uncertain but is taken to be May 27, when the last observed ejecta left the crater.
Explosive eruption column from Halema‘uma‘u Crater 11:15 a.m. May 18, 1924 – one of many in a series of similar events during May 11-27. Photo from northwest rim of Kīlauea summit, present site of HVO // Courtesy: usgs.gov
The larger explosion clouds reached several kilometers high, with an maximum of 9 km (about 5.5 mi) estimated by Ruy Finch of HVO. Trade winds were blowing from the northeast during the eruption, yet wet ash fell at least once on railroad tracks in lower Puna, northeast of Halema‘uma‘u. This is consistent with the ash cloud rising about 5 km (3 mi) or more into the jet stream wind, which blows from the west. Gutters on the roof of a store in Glenwood, 16 km (10 mi) northeast of Halema‘uma‘u, collapsed from the weight of muddy ash, also suggestive of jet-stream transport.
The explosions were powered mainly by steam, generated as groundwater came in contact with hot rocks. At Kīlauea, volcanologists think this happens when lava drains from the conduit—probably a few meters wide— connecting the lava lake and a deeper magma body. Below the water table, a conduit filled with magma keeps water out, but, once the conduit empties, groundwater can flow into the still-hot conduit, where it quickly flashes to steam. Most of the time, the steam rises up the conduit and escapes without explosion. However, the wall of the conduit, which is no longer supported by a filling of lava, collapses from time to time, temporarily impounding the steam. The steam quickly builds up pressure, and, within several minutes, overcomes the weight of the blockage and explodes the collapse debris out of the crater. As pressure is released, the explosion ends and passive release of steam resumes, only to be punctuated again by another wall collapse.
Nick is former television meteorologist with stints in Amarillo and Hattiesburg. During his time in Hattiesburg, he was also an adjunct professor at the University of Southern Mississippi. He is a graduate of both Oregon State and Syracuse University that now calls Houston home. Now that he is retired from TV, he maintains this blog in his spare time.
