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Feb 17, 2014 11:17 AM EST

Predicting Volcano Eruption Is All About Cold Magma


*This story was edited to reflect a change.

Lord of the Rings was once used in a clever study comparing its landscapes to real places in the world as part of a larger goal to strengthen climate modeling techniques. Even J.R.R. Tolken's representation of magma prior to eruption represented an accurate construction of middle earth, according to new volcano research from UC Davis and Oregon State University, Fox reported.

If Mordor and the magma stored beneath its Mt. Doom wasn't about to erupt, the super-hot liquid really should have been in a more solid state, similar to "peanut butter," according to the study's researchers. (It was almost pure liquid, allowing Frodo and Samwise to destroy the ring but barely giving them enough time to escape with their lives.)

Examining Oregon's 11,249-foot-high Mt. Hood in particular, researchers found that lava within volcanoes tends to exist in a much cooler state during periods of inactivity; it isn't mobile enough to flow up the mountain as in an eruption. The lava is still hot, however -- the "threshold level" or the point at which it begins to turn from solid to liquid is approximately 750 degrees Celsius at Mt. Hood -- and needs only to increase by 50 to 75 degrees Celsius to mobilize enough to become a threat for eruption, according to the study.

"If the temperature of the rock is too cold, the magma is like peanut butter in a refrigerator," USO geologist Adam Kent, co-author of the study, said in a statement. "It just isn't very mobile. For Mount Hood, the threshold seems to be about 750 degrees (C) - if it warms up just 50 to 75 degrees above that, it greatly decreases the viscosity of the magma and makes it easier to mobilize."

Exceeding 750 degrees (C), or 1,382 degrees Fahrenheit, happened when Mt. Hood blew during its last two eruptions, 220 and 1,500 years ago.

According to the study, magma is only in a mobile state less than 10 percent of the time. Though Kent and fellow researchers haven't confirmed this mechanism for all volcanoes, they don't believe Mt. Hood is the exception. Thus, they've found a relatively straightforward way to predict when certain volcanoes will erupt or when they're likely to erupt.

"This tells us that the standard state of magma for this system is that it can't be erupted," Kari Cooper, a geochemist at UC Davis and study co-author, told Fox. "That means that having a magma that can erupt is a special condition. Our expectation is that there's a lot of volcanoes that behave this way."

"If you can see a body of magma that has a high amount of liquid, perhaps this magma is getting ready to erupt or at least has some potential to erupt," said study co-author Adam Kent, a geologist at Oregon State University. "It wouldn't be a slam-dunk guarantee."

As per a previous study, when liquid magma forms and begins to mix with solid magma, the proportion of one to another can also predict the magnitude of an eruption. Luckily for its residents, Mt. Hood doesn't erupt in the glorious fashion that Doom did.

"What happens when they mix is what happens when you squeeze a tube of toothpaste in the middle," said Kent. "A big glob kind of plops out the top, but in the case of Mount Hood - it doesn't blow the mountain to pieces." 

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