The Explosive History of Kilauea

My family and I love the Big Island. We visit as often as we can, particularly over the New Year's holiday. That's not happening this year, unfortunately, making me especially wistful for Hawaii County. But while we won't be able to vacation in the cool, lush rainforests of Volcano Village, a story in the news has made our regular pilgrimage seem a little less alluring.

Last week, USGS scientist Don Swanson was speaking at the American Geophysical Union conference in San Francisco. And his talk focused on a lesser known aspect of Kilauea.

Kilauea volcano has been continuously erupting since 1983, and it has been relatively peaceful through most of recorded history. But that's a very brief period in geologic time. And after carbon-dating charred plant life dating back over 2,000 years, it looks like Kilauea has been much more volatile, and for longer periods than previously thought.

BBC News declared, "Two-faced Kilauea volcano exposed." Discovery News wrote of "Kilauea's killer mood swings." We covered the story on "Bytemarks Cafe" on Wednesday.

I was interested enough in Swanson's comments to transcribe the audio of his interview with the BBC. His comments are certainly a good reminder that the good graces of Mother Nature (or Madame Pele) is never something you can take for granted.

"Kilauea is certainly one of the most famous volcanoes in the world. The lava flows, the fountains, the beauty, and it's not realized that Kilauea is quite a dangerous volcano, too.

Kilauea is a volcano people flock to when it's erupting lava flows, but people haven't experienced the very dangerous explosive eruptions from Kilauea that we know it's had so frequently in the past. When that kind of activity happens, people won't be coming to the volcano, they'll be fleeing from the volcano.

Once Kilauea gets into an explosive period, this period can last for several centuries. They're not just blips on the screen that goes away in a few days or a few weeks. So once we get into that period, then our feeling about Kilauea will be vastly changed from the public's feeling about Kilauea now.

We think what's driving the explosive eruptions is generally the interaction with groundwater. Groundwater or surface water is heated up to steam. This is pressurized if rocks are falling in to the conduit and trapping the steam from escaping. Pressure has to build up, then eventually the pressure breaks through and throws rocks onto the surroundings.

There is one exception to this, though. We think about 1200 years ago there was a carbon dioxide driven explosion. It's largest one that we know of. We're not sure if that requires any interaction with groundwater, if it's CO2 driven. These are dangerous explosive events. The evidence for that are the several hundred people that were killed by an explosive eruption in 1790.

Today, 5,000 people visit that area, and probably not one knows of these fatalities that took place 200 years ago, and it could happen again if people are not aware of what's happening. They should be aware, though — there should be enough forewarning. The caledra will drop to the water table where groundwater can interact, and we'll know that, and be able to tell people, 'Don't come into the area.' There'd be no reason for people to lose their lives if they're prudent.

This would be a profound change. The communities at the summit of the volcano would have to be evacuated and remain so. They would simply be abandoned for potentially a few hundred years, and that would have a dramatic impact on the island. Furthermore, so many people come to Kilauea, tourist money is important to the island economy. When people can't come to the summit, the national park would probably be closed, and that would impact the economy.