AsianScientist (May 25, 2016) – Taking inspiration from old engineering basics, a study has shed new light on the connection between earthquakes and volcanoes, where the former can cause the latter to erupt. Future applications of these results, published in the Journal of Volcanology and Geothermal Research, may enable better predictions of the likelihood of a volcanic eruption for communities affected by earthquakes.
If you swirl wine in a glass too strongly, the wine crashes against the sides and spills over the top. The same swirling and crashing, technically termed ‘sloshing,’ happens when transporting liquids on trucks or ships. Large liquid containers must be specially designed to avoid damage as the vehicle shakes and the liquid sloshes. Strong earthquakes can even damage large petroleum tanks.
When earthquakes shake the ground, the hot, molten rock beneath the Earth’s surface can slosh and cause magma to erupt from volcanoes.
“I wondered how earthquakes shake magma underground,” said first author, Associate Professor Atsuko Namiki from Hiroshima University. “It is well known that some earthquakes can trigger volcanic eruptions, but exactly how earthquakes and volcanoes are connected is still controversial.”
“Our work adds a new event—earthquake-induced sloshing—to the list of possible triggers of volcanic eruptions.”
In a surprisingly simple setup, the researchers filled boxes with simple syrup to represent a volcano’s molten insides. A precision shake table represented an earthquake.
“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 side-to-side shaking we used represented earthquakes of different severities and intensities.”
Air bubbles and small plastic flakes added to the syrup represented the bubbles of gas and solid crystals floating in magma. The research team then used a super-fast camera and advanced mathematical calculations to analyze video recordings of the model volcanoes.
During ‘earthquakes’ of certain strength and speed, sloshing popped bubbles inside the syrup. In an actual volcano, popped bubbles release volcanic gas into the atmosphere. This decrease in pressure within the volcano can then trigger an eruption.
“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,” said Namiki.
Sloshing mixes the layers, which can trigger the growth of new bubbles that eventually pop and create more violent eruptions.
The research team analyzed the syrup’s motion and created a model to describe the conditions under which bubbles in real magma could pop and potentially cause actual volcanic eruptions.
Buildings suffer greater damage when the building’s resonant frequency matches the rate of shaking by the earthquake. Similarly, volcanoes have resonant frequencies and certain earthquakes will more significantly slosh magma inside a volcano.
The shape of the inside of the volcano and the location, size, and number of bubbles all influence how a volcano might behave after an earthquake. Depending on the volcano, some earthquakes could trigger volcanic eruptions within weeks; others might take years.
The results indicate that the historically documented increase in the number of volcanic eruptions after an earthquake has an explanation and is not just coincidence.
The article can be found at: Namiki et al. (2016) Sloshing of a Bubbly Magma Reservoir as a Mechanism of Triggered Eruptions.
Source: Hiroshima University.
Disclaimer: This article does not necessarily reflect the views of AsianScientist or its staff.