An international group of geologists and earth scientists from Iceland, the United Kingdom, and the United States has proposed a fresh explanation for how lava fountains form during volcanic eruptions. The team published their findings in a peer-reviewed science journal, sharing new insight into the dynamics that drive spectacular lava displays during eruptions.
Volcanic eruptions rank among nature’s most dramatic events. A volcanic peak ejects molten rock skyward, sometimes with towering jets of lava. Yet the precise processes that ignite and sustain these fountains—along with what energizes them—remain topics of ongoing study.
The researchers drew on the 2021 activity at Fagradalsfjall, an eruption that surprised observers with a sequence of lava fountains reaching different heights rather than a single, steady plume. This eruption served as a natural experiment to test ideas about how fountain formation begins and evolves over the course of an event.
The proposed model centers on a shallow magma-filled chamber beneath the volcano’s caldera. As magma rises into this cavity, volatile gases escape, creating a foamy layer that sits atop the molten rock inside the chamber. The foam acts as a pressure cap, trapping gases until a rupture occurs.
When the foam layer cracks, the built-up pressure is released, pushing magma upward into the conduit and ultimately into the air as a fountain. The characteristic repetition—the rise of subsequent bursts and the varying heights of the jets—appears to result from cycling gas production that continually reforms the foam layer within the cavity. Each cycle builds on the last, producing the rhythmic sequence of eruptions seen at Fagradalsfjall and similar systems.
This foam-driven mechanism offers a way to understand why fountains can appear in quick succession and with changing vigor rather than as a single, uniform plume. It also aligns with observations from underwater and coastal eruptions where magma interacts with water-rich surroundings, influencing how pressure builds and releases in real time.
Beyond Fagradalsfjall, the model may help explain fountain activity in other volcanoes that show episodic jets and complex fountain heights. The approach emphasizes how shallow magma storage zones interact with gas buildup and rapid pressure release to shape eruptive style. These insights contribute to a broader effort to map the link between magma dynamics, gas content, and surface expressions of volcanic energy, which has practical implications for hazard assessment and early warning in volcanic regions around the world.
In a broader sense, the research highlights how careful interpretation of eruption sequences—paired with field observations, remote sensing, and numerical modeling—can reveal the hidden architecture of a volcano’s plumbing system. By focusing on the interplay between gas-driven foams, conduit constrictions, and magma supply, scientists are building a more cohesive picture of what makes fountains rise, fall, and reconfigure over the course of an eruption. The findings underscore the value of studying a diverse set of eruptions, including those that depart from textbook patterns, to capture the range of behaviors that volcanoes can exhibit in nature.