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Volcano Watch — New assessment of U.S. volcano threats points to needed monitoring improvements

News stories have appeared widely in the past week spotlighting the "most dangerous" volcanoes in the United States, including a few in our backyard.

Explosion column from Halemaumau, Kīlauea
Explosion column from Halemaumau, Kīlauea, on May 13, 1924, at 09:35am. Photo taken from near Kīlauea Military Camp.

These stories were spurred by a report released last week by the U.S. Geological Survey. The report evaluates more than a hundred volcanoes in the U.S. that threaten people, property, or aviation safety and recommends a strategy to enhance the ability of scientists to provide reliable warnings of impending eruptions in time to implement response plans and mitigation measures.

This is a challenge scientists and governments have faced ever since the world's earliest volcano observatories were established in Italy, Hawaiʻi, and Japan. It was the driving force behind the creation of the Hawaiʻian Volcano Observatory in 1912 by Dr. Thomas Jaggar and his supporters.

The new report is the most comprehensive to date for evaluating the nation's increasing exposure to volcano activity, combined with a detailed assessment of existing volcano-monitoring systems. The authors assessed whether volcanoes that are currently erupting or could erupt are being watched by scientists very well, not well enough, or not at all.

The authors began by asking a couple of questions. Which volcanoes are the nation's most threatening in terms of people and resources that would be exposed to future eruptions? Are these volcanoes monitored at the level warranted by the threat? The answers to these questions define the monitoring improvements needed for each volcano relative to the potential threat they pose.

Such questions are not new. But the scope of the evaluation is much more extensive for several reasons.

A total of 169 U.S. volcanic systems were evaluated for their threat. Earlier volcano reports only looked at about 70 volcanoes. The new expanded list includes volcanoes that are currently erupting or showing signs of unrest, those that have erupted in historical time, and those that have not erupted recently but are young enough (eruptions within the past 10,000 years) to be capable of reawakening.

Also, each volcano was ranked according to 15 hazard factors and 10 exposure factors. Hazard factors include whether a volcano has produced significant explosive eruptions, lava flows, tsunami, earthquake activity, eruptions that resulted in fatalities, and current signs of swelling or deformation.

Exposure factors include population on or near a volcano, known fatalities, major nearby developments, transportation routes, and threat of volcanic ash to aircraft and airports.

With all these criteria, it is not surprising that Kīlauea ranks at the top of the threat list of 169 volcanoes. Kīlauea has had many explosive eruptions over extended periods of time during the past 1,500 years, and explosive activity in 1790 killed at least 80 Hawaiʻians. The 1980 eruption of Mount St. Helens killed 57 people.

Familiar to everyone living on Kīlauea, the volcano has produced many lava flows over broad areas that have covered forests, communities, roads, and buildings, and resulted in evacuations. Large earthquakes, some of which triggered local tsunami, are common beneath the volcano, as are high rates of ground deformation and widespread degassing from fissures and fumaroles.

Other Hawaiʻian volcanoes ranked as follows: Mauna Loa 8th, Hualālai 30th, and Mauna Kea 97th.

Much of the recent concern over potentially active volcanoes, however, is based on the threat to aviation, which is not much of a problem during typical Hawaiʻian eruptions. Explosive eruptions threaten aviation safety when finely pulverized, glassy, abrasive ash reaches the cruise altitude of aircraft and disperses over thousands of miles.

Numerous instances of aircraft flying into volcanic ash clouds in the past 25 years have resulted in hundreds of millions of dollars of damage and seven cases involving engine failure. The need for rapid dissemination of eruption information will increase as the airline industry introduces changes such as more free-flight routing and extended twin-engine operations

Next week we will discuss what the report suggests for the future of volcano monitoring in Hawaiʻi and infrastructure requirements needed to bolster the effectiveness of the existing five USGS volcano observatories and University partners to acquire, analyze, and disseminate volcano monitoring data and emergency information.

Volcano Activity Update

Eruptive activity at Pu`u `O`o continues. Glow is visible from several vents within the crater on clear nights.

The PKK lava tube continues to produce intermittent surface flows from above the top of Pulama pali to the ocean. Lava is currently entering the ocean at both East Lae`apuki and Kamoamoa, and surface flows are active inland of both entries. The East Lae`apuki entry is the closest activity to the end of Chain of Craters Road, in Hawai`i Volcanoes National Park, and is located about 4.7 km (3 miles) from the ranger shed. Expect a 2-hour walk each way and bring lots of water. Stay well back from the sea cliff, regardless of whether there is an active ocean entry or not. Heed the National Park warning signs.

During the week ending May 4, one earthquake was reported felt on Hawai`i Island. A magnitude-2.7 quake occurred 7 km (4 miles) northwest of Kalapana at a depth of 4 km (2.5 miles) at 4:59 p.m. on Wednesday, May 4; this earthquake was felt at Kalapana.

Mauna Loa is not erupting. During the week ending May 5, 6 earthquakes were recorded beneath the summit area. Four were deep and long-period in nature. Inflation has slowed beneath the summit over the last few weeks.

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