Could a volcanic disaster like Mt. Ontake hit The Big Island? (Hilo: suite, rich)

[OpenD]

The executive summary is: Highly Unlikely

I doubt that I'm the only person who has wondered about this. The horrifying news stories over the weekend told us us that perhaps 31 hikers on Japan's Mt. Ontake were killed by an explosive volcanic eruption, with no warning, which was essentially inescapable for those on the upper slopes. Apparently they were totally engulfed in fine ash that literally choked them, and then buried under fine ash up to 20 inches thick.

So I went to the best people I can think of to answer the question, the staff at the Hawai'i Volcano Observatory (HVO), located on the rim of Kilauea inside the Volcanoes National Park. I was particularly interested in whether the large number of sensors deployed on the Big Island and the constant monitoring would give us warning of possible events like this. And here's the answer I was given...

"The short answer is yes, but there would need to be special conditions. They are:

1) A vent that is emitting gas pretty continuously
2) Collapse of the vent walls for one to several minutes, so that gas can't escape passively and instead builds up pressure behind the "dam"
3) People near enough to be impacted by the fallout from the explosion

A small-scale example of such an event (minus people in harm's way) happened on March 19, 2008, when a gas vent in Halemaumau, the summit caldera at Kilauea, was blocked by collapse of the vent wall for about 1 minute. Gas pressure eventually overcame the weight of the collapse debris, and a very small explosion took place, ejecting blocks weighing more than 200 kilos onto the ground surface 80-100 m higher. Fine ash from the eruption spread southwestward, dispersed by the trade wind.

Monitoring will probably detect changes that provide warnings. However, such changes may linger for days or weeks, and an explosion could take place at any time within that period.

I don't know yet exactly what happened at Ontake, but the photos and interviews suggest a fall of ash rather than a pyroclastic flow. Had it been a flow, there would be reports of burns and blown-away structures. Instead, all structures appear to be intact except for the cover of ash."

So, a little less to worry about...

[whtviper1]

Did you call them? Or, see them in person? That might make nwcountrygal feel better.

[Mark.ca]

If i'm not mistaking Kilauea is a shield vulcano while the one in Japan is composite. 2 very different types with different behaviors. Puna should be safe...relatively.

[hawaiian by heart]

I believe if you want to cause chik'n'skin? The possibility of multiple volcanoes on the big island erupting at the same time is higher then having a Mt. St Helens or Mt. Ontake type euruption or incident. Because the makeup of hawaiian volcanoes lava and rock is different, unlike the St. Helens or Ontake gasses can escape from hawaiian volcanoes. Thus is why you don't have the same explosive eruptions on the big island.

As i was saying multiple volcanoes eurupting or being active at the same time is more likely and has happened. Hualalai erupted seven times in the last 2,100 years. The only historic eruptions were in 1800 and 1801. Mauna Loa last erupted in 1984 and sent flows towards Hilo. Kilauea has been erupting since 1983.

Loihi, a submarine volcano, is 15 miles (24 km) southeast of the island and 3,178 feet (969 m) below sea level. Loihi will probably not reach sea level before 250,000 years or more. Seismicity, geothermal vents, and fresh lava indicate Loihi is active.

Maunia Loa is overdue.

[OpenD]

Originally Posted by Mark.ca

If i'm not mistaking Kilauea is a shield vulcano while the one in Japan is composite. 2 very different types with different behaviors. Puna should be safe...relatively.

I suppose if I stopped and thought about I might have had that thought, although from what I was told by Jim at HVO, I'm not sure it's a relevant distinction. It seems that undetected gas buildup was likely the culprit, and the HVO's sensor should detect such a problem in advance, except in very unusual cases.

And to tell the truth I wasn't thinking of Puna as much as I was the Kona side of Mauna Loa, where a lot of hikers can often be found, downhill from an active caldera near the peak. And per the HVO history on their website, Mauna Loa usually doesn't erupt while Kilauea is erupting, but on the other hand it had been erupting about every 5 years until Kilauea interrupted its cycle back in 1983, and Kilauea hasn't stopped erupting ever since.

But again, I think that today there would be plenty of notice of such an occurrence , and a timely warning.

HVO Mauna Loa Status

[Fredesch]

i don't think you will see the same thing in Hawaii as what happened in Japan. Volcanos that spew ash usually have a different chemical make up than volcanoes that usually flow lava. I believe volcanoes that spew ash and have tuff flows have a higher percentage of silica than the volcanoes in Hawaii. The chemical difference causes differences in viscosity, minerals formed and different behavior.

Volcanoes in Hawaii have lava rich in mafic (magnesium/iron suite) of elements and form basalts. The magmas viscosity and chemical composition will form fountains and throw bombs. With scoria forming when there is a lot of gas. Since Hawaii is in the middle of the ocean, there are no sources of silica to switch a mafic rich lava flowing volcano into a ash throwing tuff flowing volcano.