Some earthquakes could trigger volcanic eruptions within weeks, others might take years.
What happens when you swirl wine in a glass too strongly? The wine crashes against the sides of the glass, splashing and spilling over the top. This swirling and crashing is termed “sloshing” and according to a new study, when earthquakes shake the ground, the hot, molten rock beneath Earth’s surface can slosh, causing magma to erupt from volcanoes.
"I wondered how earthquakes shake magma underground. It is well known that some earthquakes can trigger volcanic eruptions, but exactly how earthquakes and volcanoes are connected is still controversial," said Atsuko Namiki, associate professor at Hiroshima University and first author of the paper, in a press release.
Namiki traveled to the GFZ German Research Center for Geosciences to use specialized equipment, and to collaborate with co-authors of the study, Eleonora Rivalta, Heiko Woith, and Thomas R. Walter.
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The team filled boxes with simple syrup to represent a volcano’s molten magma, and added air bubbles and small plastic flakes to the syrup to represent the bubbles of gas and solid crystals that float in magma. "It might be surprising that ordinary syrup can represent a volcano's magma, but the way syrup moves is quite similar to magma," said Namiki.
The boxes were placed on a precision shake table, which is used to recreate different severities and intensities of an earthquake. A super-fast camera and advanced mathematical calculations were then used to analyze the video recordings of the model volcanoes.
Photo credit: Atsuko Namiki/Hiroshima University
Caption: Snapshots of the same box filled with green simple syrup, as well as bubbles and plastic flakes (grey color). The box was first at rest (left) and then shaken side-to-side (right).
According to the results published in the Journal of Volcanology and Geothermal Research, during earthquakes of certain strengths and speeds, sloshing popped bubbles inside the syrup. However, "in sealed containers, sloshing only occurs when there is empty air space where the liquid has room to move. Most magma reservoirs in volcanoes are full and sealed, but sloshing still can occur if there are layers of magma of different densities, similar to oil floating on water," Namiki explained.
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In an actual volcano, sloshing can mix the layers, triggering the growth of new bubbles that eventually pop, releasing gas into the atmosphere. This decrease in pressure within the volcano can then prompt an eruption.
By analyzing the syrup’s motion, the research team concluded that when a volcano's resonant frequency, or natural vibration, matches the rate of shaking by an earthquake, more magma will be sloshed inside a volcano. But the shape inside of the volcano, along with the location, size, and number of bubbles, all influence how a volcano may behave after an earthquake. Depending on the volcano, some earthquakes could trigger volcanic eruptions within weeks, and others might take years.
The researchers hope the results can be used to produce better predictions of the likelihood of a volcanic eruption for regions recently affected by an earthquake.
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