Microscopic Bubbles Can Tell the History of Earth's Massive Volcanic Eruptions

Experts have become very interested in the microscopic bubbles that accumulate in a magma reservoir underneath a volcano. They believe that these microscopic bubbles hold the history of the biggest volcanic eruptions on Earth, such as Mount St. Helen in 1980, Mt. Pinatubo of the Philippines in 1991, and Mount Chaitén of Chile in 2008.

Geoscientists learned that some of these stories could be written in nanoparticles. They worked hard for five years to reconcile the differences between numerical models that predict the number of bubbles that will form and the actual bubbles that formed during an eruption.

They published their study in Nature Communications.

Determining Volcanic Eruption Intensity

Sahand Hajimirza, a postdoctoral researcher, said that the intensity of eruption refers to the amount of magma erupted and how quickly it comes out. For example, the Plinian eruptions range from 10 million kilograms per second to 10 billion kilograms per second.

Scientists study the microscopic bubbles in erupted lava and ash to gauge the speed of rising magma. These bubbles are similar to the bubbles in uncorked champagne, which are created by a rapid decrease in pressure.

"As magma rises, its pressure decreases," Hajimirza says. "At some point, it reaches a pressure at which water is saturated, and further decompression causes supersaturation and the formation of bubbles."

As water escapes in the form of a bubble, it makes the molten rock less saturated, according to Futurity. However, the faster the magma rises, the higher the decompression rate and supersaturation pressure to create more nucleated bubbles.

For instance, the Plinian eruptions released so much magma, creating a staggering amount of bubbles. When Mount St. Helens erupted, it spewed over one million billion bubbles in each cubic meter of rock and ash. The total number of bubbles is septillion or 1,000 times the number of grains in the sand on Earth's beaches.

ALSO READ: Deadly Lava Lake Is Bubbling in Hawaii's Kilauea Volcano Hitting Extreme Temperatures

Bubbles Move Through Crystal-Rich Areas of the Magma

Hajimirza says that when bubbles nucleate, they can form in liquid, called homogeneous nucleation, or in solid, called heterogeneous nucleation. An example of that is how bubbles in boiling water form in the bottom of the pot, which is heterogeneous nucleation.

In rising magma, heterogeneous nucleation begins earlier at a lower supersaturation level wherein the surfaces that the bubbles nucleate are often on tiny crystals.

According to Science Daily, bubbles would ascend much faster in crystal-rich zones and accumulate in the melt-rich portions above. Study author Andrea Parmigiani explained that the existing highly viscous melt would be displaced when the proportion of bubbles in the crystal-rich layers' pore space increases.

Their study primarily focuses on understanding the basic principles of the gas flow in magma reservoirs, which could hopefully be applied in predicting volcanic behavior. Forecasting volcanic eruptions are the lifelong and challenging dream of volcanologists as they could not observe the volcano's subsurface to know what is happening.