Mount Vesuvius is synonymous with one of history’s greatest natural disasters: the catastrophic burial of Pompeii and Herculaneum in 79 AD. Located just east of the densely populated city of Naples, Italy, the volcano remains an active reminder of volatile forces beneath the Earth’s surface. Many people wonder whether the iconic mountain will erupt again. Vesuvius is not extinct; it is classified as an active volcano, currently in a resting or quiescent state.
The Geologic Status of Vesuvius
Vesuvius is classified as a Somma-stratovolcano, a complex structure featuring a large caldera, Mount Somma, with a younger cone growing within it. This explosive formation exists due to an active subduction zone where the African tectonic plate is sinking beneath the Eurasian plate. The melting of the subducting plate creates magma that rises to the surface, fueling the Campanian volcanic arc.
Since the 79 AD disaster, the volcano’s history has been marked by a pattern of major, explosive events followed by periods of quiescence. A notable eruption occurred in 1631, one of the most violent since the ancient Roman period. This was followed by centuries of less intense, persistent activity, including lava flows and smaller explosions.
The last significant eruption took place in 1944, destroying several villages near the base of the cone. Since then, Vesuvius has entered a “closed conduit” phase, meaning the central vent is sealed. It is currently characterized only by low-level seismicity and gas emissions. Scientists understand that the longer this quiescent period lasts, the greater the potential for pressure to build, increasing the likelihood of a highly explosive future eruption.
How Vesuvius is Monitored Today
Continuously tracking Vesuvius falls to the Osservatorio Vesuviano (Vesuvius Observatory) of the National Institute of Geophysics and Volcanology (INGV). This sophisticated system detects subtle precursor signals that indicate magma movement deep underground. Monitoring is broken down into three main categories: seismology, ground deformation, and geochemistry.
Seismometers constantly listen for shallow volcano-tectonic earthquakes, caused by the fracturing of rock due to rising magma or fluid pressure. These tremors are low to moderate in magnitude and are concentrated along the central conduit, often up to six kilometers below sea level. An increase in the frequency or depth of these quakes would be an immediate sign of unrest.
Ground deformation is measured using Global Positioning System (GPS) networks and tiltmeters positioned across the volcano’s flanks. GPS instruments track subtle horizontal and vertical shifts in the ground, while tiltmeters measure minute changes in the slope, or “tilting,” of the volcano’s surface. Any measurable swelling or inflation of the volcano’s cone could signal a buildup of pressure from a shallow magma body.
Geochemical monitoring involves analyzing the composition and flow of gases emitted from fumaroles on the crater rim and floor. Scientists continuously measure the flow rate of carbon dioxide (CO2) from the soil and analyze the chemical and isotopic makeup of the gases. Changes in gas ratios, particularly a sudden increase in magmatic gases like CO2 or sulfur, indicate that fresh magma is rising and interacting with the hydrothermal system.
Assessing the Eruption Likelihood and Scale
Vesuvius is currently quiet, but it will erupt again, making it one of the most dangerous volcanoes globally due to the surrounding population density. The current alert level remains at Green, indicating ordinary, non-eruptive activity based on monitoring data. Alert levels would shift to Yellow, Orange, and finally Red as precursor signals intensify, signifying an increasing probability of an eruption.
A future event is likely to be explosive, in the Plinian or Sub-Plinian style, similar to the 79 AD and 1631 eruptions. This type of eruption is characterized by a high-reaching column of ash, gas, and rock. This leads to two significant hazards: fast-moving, high-temperature pyroclastic flows and widespread fallout of ash and lapilli. Pyroclastic flows are considered the most lethal hazard, as they are impossible to outrun.
The most vulnerable area is defined as the “Red Zone” (Zona Rossa), which encompasses the territory at risk of being directly inundated by pyroclastic flows or suffering catastrophic structural damage from heavy ash fall. This zone includes 25 municipalities and parts of Naples, containing 700,000 to 800,000 residents who would require mandatory, preventative evacuation. The Italian Civil Protection Department has estimated a target of 72 hours to complete the evacuation once the official alarm is raised.