Volcanic eruptions may be easier to predict once the magma cools down, according to a new research. This information was unearthed from a study of crystals.
Data was collected from two eruptions of Mount Hood. The first of these events occurred 1,500 years ago, and the second, 200 years before our time. Each time the volcano erupted, crystals were created. These provide a history of the events leading to the eruptions, including temperatures during the events.
One surprising finding showed crystals were trapped in cool lava, full of minerals, from which the crystals were formed. The magma was too cool to erupt, according to the study, and may have stayed that way for 100,000 years before the first eruption.
For Mount Hood, that reservoir of molten rock lies nearly three miles underground. The temperature averages 1,380 degrees Fahrenheit. This may seem hot, but this is too cool to initiate a volcanic eruption. Researchers believe if the temperature of the magma increased by as little as 200 degrees Fahrenheit, it could trigger another eruption. Still, there is no need to worry just yet.
"This tells us that the standard state of magma for this system is that it can't be erupted. 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," Kari Cooper, professor of geology at the University of California, said.
Mount Hood was formed when one continental plate was pressing into, and under, a second one, in a feature called a subduction zone. As the crust is pushed into the ground, it heats and melts rocks, leading to the rise of volcanoes.
Researchers believe hot magma, rising from beneath the crust of the Earth, is needed to set off the eruptions. Eruptions may be predicted by studying the movement of this magma, as well as the temperatures within the structures. This type of monitoring would be useful for most volcanoes in the world. However, in areas like Hawaii, where the structures are located over hot spots in the Earth's crust, the effect may not be effective in predicting eruptions.
"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. It wouldn't be a slam-dunk guarantee," Adam Kent, study co-author and professor of geology at Oregon State University, told Live Science.
When crystals make up more than 50 percent of the magma contained in a volcano, the substance becomes too thick to leak from cracks. Instead of having a boiling, liquid consistency, magma may be as thick as peanut butter between eruptions, according to the new research. This prevents eruptions from occurring.
The study of crystal structures within Mount Hood was published in the journal Science, on 16 February.
