MARY LOUISE KELLY, HOST:
The world's largest active volcano is erupting for the first time in almost four decades. That would be Mauna Loa on the Big Island of Hawaii. The U.S. Geological Survey says lava flows are not currently threatening communities, but it is keeping watch.
And joining us from the USGS is volcanologist Wendy Stovall. Hey there.
WENDY STOVALL: Hey there. Happy to be here.
KELLY: Glad to have you with us. And I guess that's kind of my first question, which is, how should we be feeling about this? Is this a natural disaster, an exciting geological phenomenon? Is it a little bit of both?
STOVALL: Let's call it the latter and not both. This is certainly an exciting thing. We have kind of been waiting for Mauna Loa to erupt for a few years now. So it is erupting, and it is not threatening anyone, as you said. So this is a really exciting thing to watch, and it's going to help us learn more about the volcano. And we are definitely keeping aware and ensuring that we provide all safety information if it comes to that point.
KELLY: Yeah. And when you say you've been kind of watching and waiting for this one - I know there have been swarms of small earthquakes up to 100 times a day. Can you, in layman's terms, explain what is happening under the surface?
STOVALL: Yeah, sure. So a couple of months ago, we noticed that Mauna Loa was kind of going into an elevated state of unrest, so getting a little bit more restless. She was doing that by causing earthquakes in the ground as magma moved into the volcano. So magma forces rocks to break. It causes earthquakes. We can detect that with our instruments on the surface.
The other thing that happens when magma moves into a volcano is that it swells a little bit. And so our GPS instruments were telling us that the volcano was swelling as well. And those were just occurring at a higher rate than we had seen in the prior couple of years.
KELLY: And what is happening there right now? I know this eruption began around midnight in Hawaii. What's the latest?
STOVALL: It was confined into the summit caldera for the beginning phase of the eruption. After a few hours, it progressed into the Northeast Rift Zone. And the rift zone is really just an area that is a preferential pathway for magma to move in the volcano. There are two of them, and it moved into the northeast side of the volcano. Three fissures are erupting from the ground, and they are spouting fountains of lava that are feeding lava flows that are going downslope from those fissures.
KELLY: So if I were on Hawaii - say I lived nearby. I know that your organization, the U.S. Geological Survey, is saying there is no danger at the moment right now to residents but that that could change quickly. What are the - what is the advice that you're giving to people living nearby? How should they prepare?
STOVALL: Yeah. So the prior couple of months, we were really concerned that things could turn out to be a not very good event. But fortunately, because the eruption has happened on the Northeast Rift Zone rather than the Southwest Rift Zone, which is the more dangerous side, the Northeast Rift Zone is actually a low-sloping side. Flows are moving to the northeast, which is not in the direction of where people live. And Mauna Loa typically erupts from the same area. It doesn't move between rift zones. So we think that things are just going to stay on one side, and they're going to continue for - you know, it could be a couple of weeks.
KELLY: Right.
STOVALL: Longer eruptions have been almost a year, but we expect this to be a little bit of a shorter one.
KELLY: All right. So it sounds like we will be watching and waiting along with you. Thanks so much.
STOVALL: Yes, thank you.
KELLY: That's Wendy Stovall, volcanologist with the U.S. Geological Survey. Transcript provided by NPR, Copyright NPR.
