Volcanic Eruptions Determined by Temperatures of Stored Magma Beneath the Earth

Active volcanoes store near-solid magma beneath their surface. Although this magma can remain solid for thousands of years, it can take only a few months to heat up and cause an eruption. Mount Hood in Oregon has been the subject of an ongoing study for this topic.

Mount Hood has not erupted in 220 years. And before that, it hadn't erupted in over 1,200 years. But scientists have studied the crystals in the volcano's lava and discovered that they provide a chronological and temperature history. The magma rests between four to five kilometers beneath the surface of the volcano and if temperatures exceed 750 degrees Celsius, then the magma will rise to the surface. But it wouldn't necessarily be a violent eruption.

Adam Kent, co-author of the study and geologist at Oregon State University, described the immobile magma as "peanut butter in a refrigerator," in this EurekAlert! article. Its mobility increases with higher temperatures. Two types of magma mixing is actually thought to be the catalyst for the eruptions.

Hotter magma exists beneath Mount Hood's near-solid magma. When the hotter magma increases in temperature, it liquefies the near-solid magma and causes the two to mix. This mixture and reaction is believed to cause a volcanic eruption. But the "eruption" in this case isn't too serious.

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

Kent and his co-author Kari Cooper of UC-Davis, say that these eruptions occur when the warmer molten rock arrives at the lower levels deep in the Earth's crust. The crystals from the lavas of previous eruptions revealed age and growth rate, which allowed the scientists to determine when eruptions have occurred as well as the temperature threshold for the solid magma to begin liquefying. More findings of the study can also be found in this Fox News article.

To read more about the study, visit the published article in the journal Nature.