The southern Italian region surrounding the Campi Flegrei volcano has experienced over a thousand small earthquakes in recent months, raising concerns of a potential eruption after nearly five centuries of dormancy. Similarly, scientists have been observing similar seismic activity and ground deformation at the Long Valley Caldera, an adjoining volcano to Mammoth Mountain in eastern California, which is approximately 6,000 miles away.
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Experts suggest that neither the Long Valley Caldera nor Campi Flegrei are currently at risk of erupting. These two volcanoes are actually calderas, which are large depressions formed by previous “super-eruptions” that caused the mountainous structures to collapse inward. Calderas pose a greater challenge in terms of predictability compared to the more recognizable towering volcanic formations.
While seismic activity can serve as a potential indicator of an impending eruption, the full story is much more complex.
Campi Flegrei and the Long Valley Caldera are categorized as supervolcanoes, defined by having erupted over 240 cubic miles of material in a single event. However, geophysicist Michael Poland, who oversees the Yellowstone Volcano Observatory, warns that the term “supervolcano” can be misleading. Although Campi Flegrei and Long Valley have the potential for massive explosions, current assessments suggest that significant eruptions are unlikely in the near future.
Campi Flegrei’s last eruption occurred in 1538, with one of its most significant explosions happening around 39,000 years ago.
Due to their expansive magmatic systems, calderas like Campi Flegrei and Long Valley are inherently complex and challenging to comprehend. For instance, Campi Flegrei spans a range of seven to nine miles, while California’s Long Valley Caldera is roughly ten miles wide.
While seismic activity has been ongoing at the Long Valley Caldera for decades, including a spike in the 1980s, scientists are currently less concerned about a major eruption in the near future. This is attributed to indications of cooling magma beneath the surface.
While eruption cannot be entirely ruled out, researchers have discovered that the magma chamber within the Long Valley Caldera is supported by a solid rock structure, which likely prevents large-scale eruptions.
