A recent eruption of the Fagradalsfjall volcano in Iceland has given scientists a rare opportunity to study the formation and behavior of lava fountains, which are spectacular jets of molten rock that can reach hundreds of meters high.
By analyzing the gas emissions and the chemistry of the lava, a team of researchers has proposed a new theory to explain how these fountains are generated and why they occur in cycles.
The mystery of volcanic fountaining
JEREMIE RICHARD/AFP via Getty Images
Volcanic fountaining is a phenomenon that occurs when a volcano erupts in a way that resembles a fountain of water, with lava shooting straight up into the air before falling back down to the ground.
This type of eruption is different from the explosive ones that produce ash clouds and pyroclastic flows, or the effusive ones that produce lava flows and domes.
Volcanic fountaining is often associated with basaltic magma, which is low in silica and viscosity, and high in gas content.
However, the exact mechanism and dynamics of volcanic fountaining are still poorly understood, as they are difficult to observe and measure in real time.
Some previous theories have suggested that fountaining is driven by the rapid ascent of magma through narrow conduits, or by the accumulation and release of gas bubbles within the magma chamber.
But these theories have not been able to account for the variability and periodicity of fountaining, which can range from seconds to hours.
The Fagradalsfjall volcano, located on the Reykjanes Peninsula in southwest Iceland, erupted for the first time in almost 800 years in March 2021, and has since produced several episodes of lava fountaining.
The eruption site is relatively accessible and safe, allowing scientists and tourists to witness and document the spectacle.
A team of researchers from various institutions in Iceland, the UK, France, and Germany took advantage of this opportunity to collect data on the gas emissions and the lava samples from the volcano, using a device that performs open-path Fourier transform infrared (OP-FTIR) spectroscopy.
Based on their analysis, the researchers proposed a new theory to explain the nature of volcanic fountaining, which they published in the journal Nature Communications.
Their theory suggested that the Fagradalsfjall volcano has a shallow cavity beneath its crater, filled with magma.
As magma rises into the cavity, gases separate from the magma and form a foam layer at the top of the cavity.
The foam layer acts as a seal that prevents the gas from escaping.
However, when the pressure in the cavity becomes too high, the foam layer collapses, releasing a burst of gas and magma that forms a fountain.
The cycle then repeats as the magma and gas refill the cavity and form a new foam layer
The researchers tested their theory by comparing it with the observations of the fountaining episodes, and found that it could explain the patterns and characteristics of the fountains, such as their height, duration, frequency, and chemistry.
They also found that the fountaining was influenced by external factors, such as the wind, the atmospheric pressure, and the topography of the crater.
Implications and future research
The researchers believed that their theory could help understand fountaining in other volcanoes around the world, especially those that have similar magma properties and eruptive styles as the Fagradalsfjall volcano.
They also suggested that fountaining could be a common feature of volcanic activity on the Reykjanes Peninsula, which is located on the Mid-Atlantic Ridge, where the North American and Eurasian tectonic plates are pulling apart.
The peninsula has experienced several periods of volcanic activity in the past, and the current one could last for decades.
They hoped that their study will raise awareness and appreciation of the beauty and power of nature, as well as the importance of monitoring and protecting the environment.
