The complex link between volcanoes and seismic activities

Scientists have long debated the possibility of a connection between volcanic eruptions and seismic activity, especially in geologically complex regions like the Mediterranean basin. This area sits on a tangle of faults created by the subduction of the African plate beneath the Eurasian plate.

The interaction of these massive plates has resulted in an intricate fault system, visible through a series of geological events observed across Spain, Italy, and Greece. Among these, Italy remains particularly vulnerable, lying directly along the contact line between the two major plates.

On June 2, 2025, Italy's Mount Etna erupted in what was described as one of its most violent events in recent history. Just a day later, on June 3, an earthquake measuring 5.8 on the Richter scale struck the sea between Greece’s Rhodes Island and southwestern Turkey. The hypocenter was recorded at a depth of 68 kms.

While the eruption sent pyroclastic flows hurtling down Etna’s slopes, threatening nearby villages, the earthquake caused panic in the Turkish town of Mugla, injuring 69 people and claiming the life of a 14-year-old girl.

Volcanic history has seen its share of devastation. When Mount Vesuvius erupted in 79 AD, its pyroclastic surge buried the Roman towns of Pompeii and Herculaneum, killing thousands. In 1902, Mount Pelée in Martinique erupted with such force that it wiped out the entire city of Saint-Pierre, claiming 30,000 lives in minutes.

Understanding the relationship

Earth’s outer crust—the lithosphere—is made up of solid rock, broken into massive tectonic plates that float over a semi-fluid mantle. These plates fit together like a jigsaw puzzle, covering both land and ocean. Their boundaries are zones of intense geological activity. When plates collide, diverge, or slide past each other, the movement generates earthquakes and, often, volcanic eruptions. Subduction zones—where one plate is forced beneath another—are particularly prone to both.

Volcanoes and earthquakes often occur in the same regions due to tectonic activity, but the relationship between the two isn't always straightforward. Not every earthquake triggers a volcanic eruption, and not every eruption is preceded by a quake.

In July 2019, Southern California experienced two major earthquakes within 24 hours—magnitudes 6.4 and 7.1. This sparked public concern about a possible eruption in Yellowstone. But Mike Poland of the US Geological Survey clarified that such quakes, while strong, are unlikely to trigger eruptions at distant sites. He noted that while large quakes can cause micro-earthquakes at nearby volcanoes, the US West sees around ten such quakes per century, and Yellowstone hasn’t had an explosive eruption in over 70,000 years.

Poland further explained how seismic waves from a distant quake can disturb underground magma reservoirs. This movement of gas and fluid can break rocks and cause smaller earthquakes. In hydrothermal areas—like those around geysers—even a small rise in pressure can lead to micro-fractures. After the 1959 Hebgen Lake earthquake, Yellowstone recorded eruptions from 289 geysers—160 of them were entirely new.

So, did Mount Etna’s eruption trigger the June 3 earthquake in Turkey? Current scientific understanding says no. Despite the proximity in time and space, there is no confirmed causal relationship. The USGS has been clear on this: it’s a coincidence, not causation.

Still, volcanoes like Etna remain under close observation. Surveillance systems continue to evolve, with thermal imaging, gas analysers, high-sensitivity seismic sensors, and satellites monitoring even the slightest changes in ground deformation.

Warming planet, a more active crust?

At the 2025 Goldschmidt Conference in Prague, a compelling study added another layer to this discussion: climate change could be influencing volcanic activity. As glaciers retreat due to global warming, the pressure they exert on the Earth’s crust lessens. This "unloading" effect allows magma and gases beneath to expand, potentially fueling more frequent and explosive eruptions.

Lead researcher Pablo Moreno Yaeger from the University of Wisconsin–Madison said, “Glaciers tend to suppress the volume of eruptions from the volcanoes beneath them. But as glaciers retreat due to climate change, our findings suggest these volcanoes go on to erupt more frequently and more explosively.”

He warned that regions like Antarctica, New Zealand, North America, and parts of Russia deserve closer monitoring as the planet warms.

India’s seismic landscape

Back home in India, volcanic risk remains low. The country’s only active volcano lies on Barren Island in the Andaman Sea. But earthquake risk is significant. India’s seismic zones include the Himalayas, the Northeast, the Andaman and Nicobar Islands, and parts of Gujarat like the Rann of Kutch. Several quakes in recent decades—Bhuj in 2001, the Nepal quake in 2015, and the 2004 tsunami—underscore this vulnerability.

These seismic risks stem from the ongoing collision between the Indian and Eurasian plates. As this tectonic pressure builds, the need for earthquake-resilient infrastructure, early warning systems, and public awareness becomes more urgent.

While volcanoes make for dramatic headlines, it's the silent buildup of tectonic stress beneath our feet that demands consistent attention.

(The author is retired Head of Forest Force, Karnataka, and environment commentator)