How fast-rising magma contributed to deadly volcano

Magma from the deadly eruption of Irazú in Costa Rica decades ago, recently helped researchers better understand quickly erupting volcanos. Now scientists hope to learn more by investigating other volcanic sites.

NASA Earth Observatory
Alaska's erupting Pavlof volcano, in the Aleutian Islands, seen in a photo snapped from the International Space Station in May. Earthquakes deep beneath the surface may be driving some fast-moving volcanos, researchers have learned.

Molten rock from Earth's hellishly hot mantle can punch through miles of overlying crust in a matter of months, a new study finds.

Before the deadly 1963 eruption of Irazú volcano in Costa Rica, magma surged 22 miles (35 kilometers) in about two months, traveling from the mantle to the volcano's shallow magma chamber, researchers report in the Aug. 1 issue of the journal Nature. The evidence comes from geochemical tests on crystals of the mineral olivine from ash erupted in 1963. Layers in the crystals helped re-create the magma's pre-eruption journey.

"We refer to our story as the 'highway from hell,'" said Phillip Ruprecht, lead study author and a volcanologist at Columbia University's Lamont-Doherty Earth Observatory in New York.

The discovery at Irazú helps confirm other clues for high-speed magma ascents, such as deep-seated earthquakes before eruptions at Mount Pinatubo in the Philippines and Iceland's Eyjafjallajökull volcano, the researchers said. Seismic tremors struck near the mantle below Pinatubo and Eyjafjallajökull in the weeks and months before the blasts. And other geochemical tracers in lava also suggest magma could shoot to the surface from the mantle in mere months. But the new study is the first hard evidence of a fast mode in volcanoes, Ruprecht said. [Amazing Images: Volcanoes from Space]

Skipping the stairs

Despite some clues suggesting speedy magma ascents, most models of volcano plumbing were akin to a slow pipe. A volcano's magma chamber fills from the bottom, like a sink filling from its drain. Many pulses of molten rock can pump into the chamber during a volcano's lifetime. Based on geochemical evidence in lava, researchers thought the magma melts would rise a bit, mix together, and then climb a little more, until finally reaching the chamber. The long journey happens over a span of thousands to hundreds of thousands of years.

"It's like going up a set of stairs. Each step is another change," said Adam Kent, a geologist at Oregon State University who was not involved in the study. "By the time you get to the surface, the magma has been changed quite substantially."

But the new study found evidence that magma feeding the 1963 eruption skipped the stairs and took the express elevator to the surface, mixing with other molten rock only at shallow depths, around 6 miles (10 kilometers) below the Earth's surface.

"This is telling us some interesting stuff about what's driving these volcanoes, which is hot stuff coming from deep within the mantle," Kent told LiveScience's OurAmazingPlanet. "The real proof of the pudding would be to find this behavior at many different places," he said.

Does this mean that monitoring volcanoes for earthquakes more than 10 miles deep could provide early warning of impending eruptions? Not for every volcano, the researchers said. [Countdown: History's Most Destructive Volcanoes]

Potential for eruption forecasting

Irazú volcano is an arc volcano, rising above a subduction zone where two of Earth's tectonic plates collide and one dives into the mantle. Some of the most massive eruptions in history came from arc volcanoes in the Pacific Ocean's "Ring of Fire," which tower above subduction zones.

Ruprecht and co-author Terry Plank are now analyzing olivine crystals from other arc volcanoes — including those in Alaska's Aleutian Islands, Chile and Tonga — for signs of fast-rising magma. "It's clearly in every arc we've looked in. [But] in terms of an arc setting, I don't think every second volcano will have it. It will be fewer than that," Ruprecht said. Looking at more volcanoes will also help researchers understand why some melts are rabbit-quick, while others rise like tortoises.

But most monitoring systems are laid out to look at shallow depths (6 miles, or 10 km), where magma and hot fluids force their way upward before an eruption, so new networks would have to be built to monitor the deeper goings-on. (These systems currently provide weeks to months of warning before an eruption.) And volcanologists would need to figure out how to predict eruptions from deep earthquakes without too many false alarms.

"Perhaps at volcanoes like Irazú and others like it, you could focus part of your efforts on looking for these deep signatures and know that in at least a year, you could expect an eruption," Kent said. "That's pretty useful from a hazards evaluation standpoint, but trying to figure out when a volcano might next erupt is a very risky game and very difficult to do."

Email Becky Oskin or follow her @beckyoskin. Follow us @OAPlanetFacebook & Google+. Original article on LiveScience's OurAmazingPlanet.

You've read  of  free articles. Subscribe to continue.

Dear Reader,

About a year ago, I happened upon this statement about the Monitor in the Harvard Business Review – under the charming heading of “do things that don’t interest you”:

“Many things that end up” being meaningful, writes social scientist Joseph Grenny, “have come from conference workshops, articles, or online videos that began as a chore and ended with an insight. My work in Kenya, for example, was heavily influenced by a Christian Science Monitor article I had forced myself to read 10 years earlier. Sometimes, we call things ‘boring’ simply because they lie outside the box we are currently in.”

If you were to come up with a punchline to a joke about the Monitor, that would probably be it. We’re seen as being global, fair, insightful, and perhaps a bit too earnest. We’re the bran muffin of journalism.

But you know what? We change lives. And I’m going to argue that we change lives precisely because we force open that too-small box that most human beings think they live in.

The Monitor is a peculiar little publication that’s hard for the world to figure out. We’re run by a church, but we’re not only for church members and we’re not about converting people. We’re known as being fair even as the world becomes as polarized as at any time since the newspaper’s founding in 1908.

We have a mission beyond circulation, we want to bridge divides. We’re about kicking down the door of thought everywhere and saying, “You are bigger and more capable than you realize. And we can prove it.”

If you’re looking for bran muffin journalism, you can subscribe to the Monitor for $15. You’ll get the Monitor Weekly magazine, the Monitor Daily email, and unlimited access to CSMonitor.com.