Iceland Volcano Leads Geologists to New Lava Fountain Theory

A past eruption of Iceland's Fagradalsfjall volcano has led scientists to a new theory on why and how volcanic fountains form.

An international team of scientists studied a 2021 eruption of the Icelandic volcano to reach their findings, which have been published in the journal Nature Communications.

While studying the spectacular lava fountains of Fagradalsfjall, the scientists theorized that these types of low-lying volcanoes have a shallow cavity filled with magma beneath the caldera. They believe that, as the magma rises, a layer of foam accumulated by gas forms. A collapse of this layer creates pressure that then pushes the magma out of the cavity and into the air—creating the captivating lava fountains that we see.

Fagradalsfjall is known for producing particularly large lava fountains, meaning it was the perfect volcano to analyze for this study. Its last eruption in 2021 displayed a six-week episode of "uncommonly periodic lava fountaining," the study reported. These reached heights between 330 and 1,300 feet, and lasted a few minutes each.

"Understanding these lava fountains is important for several reasons," Samuel Warren Scott, a postdoctoral researcher at the University of Iceland and one of the authors of the study, told Newsweek. "Firstly, lava fountaining is a dramatic and potentially hazardous volcanic phenomenon. By comprehending its mechanics and the relationship between lava fountaining and magma degassing near the surface, we enhance our knowledge of volcanic processes."

These lava fountains were also well contained to the caldera, or craterlike basin, of the volcano, meaning it was safe for scientists to study how they were produced.

Scientists look at the lava fountains using a technique called open-path Fourier transform infrared. The process allowed the scientists to study the chemical compositions of the volcano's gases.

Although more research is needed to determine this theory, this study brings scientists a step closer to understanding why these fountains form.

The study noted that lava fountains at Fagradalsfjall contrasted with events at other well-known volcanoes such as Hawaii's Kīlauea and Italy's Etna. Both of these experienced fountaining fed by magma reservoirs of the upper crusts. However, the eruption at Fagradalsfjall volcano was fed by a magma reservoir at the crust interface.

"The striking feature of the 2021 Fagradalsfjall lava fountains was their consistent regularity, cycling on and off at intervals of 5-10 minutes. This type of fountaining behavior had not been previously observed," Scott said. "Our gas measurements showed how this behavior resulted from shallow magma degassing and pressure cycles in a shallow cavity at 50-100 m depth underlying the volcano. Secondly, as lava fountains can project volcanic material over considerable distances, a deeper insight into the physical factors driving this type of fountaining behavior can help in hazard assessment."

Many volcanoes across the world produce lava fountains while experiencing an uptick in activity. However, exactly why or how they form has never been confirmed, although there are several theories. One is that these fountains form following a rapid ascent of magma.

"Compared with Kīlauea or Etna, the fountaining events at Fagradalsfjall were extremely regular, with much shorter intervals of fountaining and repose (minutes rather than days/weeks) persisting for more than a month," the study read.

"Other basaltic volcanoes such as Kilauea and Etna have exhibited similar intermittent behavior, but over longer timescales. We propose that this difference results from the greater depth of the magma cavity underneath these volcanos. This suggests that while some of our findings might be applicable elsewhere, each volcano also has its unique plumbing system."

Fagradalsfjall volcano has been displaying greater activity in recent weeks. Thousands of residents living in the local area have been evacuated over the looming threat of a possible eruption. Earthquakes emanating from the volcano have already caused damage to electric, water and sewer lines. There have so far been no lava fountains reported during this activity.

"Studying lava fountains can indeed aid in predicting volcanic activity," Scott said. "By identifying the signs and patterns that precede fountaining, such as changes in gas emissions or seismic activity, scientists can improve their short-term forecasts of volcanic eruptive behavior. However, it's important to note that prediction remains a complex challenge due to the numerous variables involved in volcanic processes."

Update: This article was updated to include comment from Samuel Warren Scott