Monitoring Volcanic Activities: Techniques Used in Italy’s Active Zones

Picture this: you’re standing on a volcanic island in the Mediterranean, watching small explosions light up the night sky every few minutes. This isn’t a disaster-it’s just another evening at Stromboli, one of the world’s most continuously active volcanoes. But beneath this spectacular show lies a sophisticated web of monitoring systems working 24/7 to keep residents and visitors safe. Italy’s active volcanic zones, particularly around islands like Stromboli and Vulcano, showcase some of the world’s most advanced volcano monitoring techniques, combining cutting-edge technology with decades of scientific experience.

Why continuous monitoring matters for Italy’s active volcanoes 🔗

Italy sits atop a geological powder keg. From Mount Etna in Sicily to Vesuvius overlooking Naples, the country hosts some of Europe’s most dangerous volcanoes. But perhaps nowhere is volcanic monitoring more critical than on the small islands of the Aeolian archipelago-particularly Stromboli and Vulcano. These aren’t just tourist attractions; they’re living laboratories where scientists race to understand volcanic behavior that could spell the difference between life and death.

Stromboli has earned the nickname “Lighthouse of the Mediterranean” for its persistent explosive activity-small eruptions occur roughly every 10 to 20 minutes, ejecting incandescent lava and ash hundreds of meters into the air. While this “normal” activity attracts thousands of tourists annually, the volcano occasionally produces violent paroxysmal explosions that can endanger the island’s 500 permanent residents and thousands of visitors. The 2019 eruptions demonstrated this danger dramatically, with two major paroxysms in July and August causing casualties and property damage.

Meanwhile, Vulcano Island presents a different challenge. Though its last major eruption occurred from 1888 to 1890, the volcano remains very much alive, exhibiting persistent fumarolic activity-venting gases and steam that signal ongoing magmatic processes below. Since September 2021, Vulcano has been in a state of heightened unrest, with increased gas emissions and temperature changes prompting scientists to intensify their monitoring efforts.

The monitoring toolkit: seismic networks as the volcano’s heartbeat 🔗

Imagine trying to diagnose a patient’s health by listening to their heartbeat. Seismic monitoring does something similar for volcanoes. Italy’s National Institute of Geophysics and Volcanology (INGV) operates dense networks of seismometers around its active volcanoes, detecting even the tiniest earthquakes and vibrations that signal magma movement underground.

At Stromboli, the permanent seismic network includes multiple types of sensors-broadband seismometers that detect long-period waves and accelerometers that capture sudden, violent shaking. These instruments work together to identify different types of volcanic seismicity, from the regular explosions that characterize normal activity to the Very Long Period (VLP) signals that can indicate larger events brewing beneath the surface. Recent research has developed algorithms that can automatically detect and characterize VLP seismicity in near real-time, a crucial advancement for early warning systems.

During Vulcano’s 2021 unrest period, INGV deployed additional temporary seismic stations to supplement the permanent network, creating a denser array capable of pinpointing even minor changes in seismic activity. This kind of adaptive monitoring-ramping up surveillance when volcanoes show signs of restlessness-has become standard practice in Italian volcano observatories.

Listening to the volcano’s voice 🔗

Beyond traditional seismometers, acoustic sensors add another dimension to volcanic surveillance. These microphones, designed to detect infrasound (low-frequency sound waves below human hearing range), capture the “voice” of volcanic explosions. Research teams have even experimented with mounting acoustic sensors on drones to fly directly above active craters, gathering data that would be too dangerous to collect by any other means.

Geochemical surveillance: reading the volcano’s breath 🔗

If seismology is like listening to a volcano’s heartbeat, geochemical monitoring is like analyzing its breath. The gases that volcanoes emit provide crucial clues about what’s happening in the magmatic system deep underground, often giving earlier warning signs than other monitoring techniques.

At Vulcano, gas monitoring has proven particularly revealing. The island’s fumaroles-vents that continuously emit volcanic gases-act as natural sampling points. Scientists measure sulfur dioxide (SO2) flux, carbon dioxide (CO2) emissions, and other gas compositions to track changes in the volcano’s state. During the 2021-2023 unrest, geochemical data showed a remarkable pulse of magmatic fluids beginning in early 2021, with increasing SO2/H2S ratios indicating fresh magma degassing at depth.

The monitoring isn’t limited to the summit area. Networks of soil gas stations measure CO2 emissions from the ground across the island, revealing diffuse degassing that occurs through the volcanic edifice’s permeable rocks. These measurements captured dramatic changes during Vulcano’s recent crisis, with CO2 output jumping significantly and providing crucial evidence of magmatic unrest months before other parameters showed clear anomalies.

Thermal monitoring of fumarolic fields 🔗

Temperature matters. Scientists continuously monitor fumarole temperatures using both fixed sensors and periodic surveys with thermal cameras. At Vulcano’s La Fossa crater, temperature increases in fumarolic gases can signal rising magmatic activity. The monitoring shows that temperature changes often precede other observable phenomena, making thermal surveillance an essential early-warning tool.

Watching the ground move: geodetic surveys and satellite technology 🔗

Volcanoes breathe-they inflate when magma rises from depth and deflate when it drains away or erupts. Detecting these subtle ground movements requires precision instruments capable of measuring changes of millimeters or even fractions of millimeters.

Italy employs multiple geodetic techniques to track volcanic deformation. GPS stations anchored into bedrock around volcanoes continuously record their position with centimeter-level accuracy, revealing inflation or deflation patterns. Tiltmeters, incredibly sensitive instruments that can detect ground tilts of less than one microradian (roughly the angle made by raising one end of a 1-kilometer-long board by just one millimeter), complement the GPS data by providing higher-frequency measurements of ground deformation.

At Stromboli, geodetic monitoring captured inflation beginning just minutes before the 2019 paroxysmal eruptions, demonstrating that even short-term precursors can be detected with proper instrumentation. Over longer timescales, the geodetic network has tracked 30 years of ground deformation, building a comprehensive dataset that helps scientists understand normal versus anomalous behavior.

Eyes in the sky: satellite interferometry 🔗

Modern volcano monitoring increasingly relies on space-based technology. Satellite radar interferometry (InSAR) uses radar signals from orbiting satellites to measure ground deformation across entire volcanic regions with remarkable precision. This technique proved particularly valuable during Vulcano’s recent unrest, providing a synoptic view of how the entire island was deforming in response to magmatic processes at depth.

Visual surveillance: thermal cameras and real-time video 🔗

Sometimes the simplest approaches remain the most effective. Networks of cameras-both visible-light and thermal infrared-provide continuous visual monitoring of volcanic activity. At Stromboli, thermal cameras positioned at strategic locations around the volcano record explosions as they happen, automatically analyzing parameters like explosion frequency, intensity, and the temperature of ejected material.

These video surveillance systems aren’t just recording devices-they’re sophisticated analytical tools. Algorithms process the footage in real-time, extracting quantitative data about volcanic activity that can trigger alerts when conditions deviate from normal patterns. During the 2019 eruptions, video analysis revealed crucial precursory signs including increased explosion frequency and unusual spattering behavior that preceded the paroxysms by minutes to hours.

Successes: when monitoring saves lives 🔗

Italy’s comprehensive monitoring approach has enabled several notable successes in volcanic risk management. The integration of multiple monitoring techniques allowed scientists to detect anomalies weeks before the 2019 Stromboli paroxysms, even if the precise timing remained uncertain. This early detection, combined with automated early warning systems that can alert populations via sirens minutes before dangerous phenomena reach inhabited areas, represents a significant achievement in volcanic hazard mitigation.

At Vulcano, the intensive monitoring during the 2021-2023 unrest period, which saw alert levels raised to yellow, demonstrated the system’s ability to track a volcanic crisis in real-time. The multi-parameter approach-combining gas, seismic, geodetic, and thermal data-provided Civil Protection authorities with the information needed to make informed decisions about public safety, including temporary restrictions on access to high-risk areas.

The challenges and limitations of volcanic forecasting 🔗

Despite impressive technological advances, volcanic monitoring faces inherent limitations. Volcanoes remain fundamentally unpredictable systems where sudden changes can occur with little or no warning. Phreatic explosions-steam-driven eruptions caused by groundwater interacting with hot rocks-can happen at any time without precursory signals detectable by current monitoring systems.

The 2019 Stromboli case illustrates this challenge. While monitoring detected changes in activity weeks before the major eruptions, the specific timing and magnitude remained uncertain until the events occurred. Scientists identified inflation of the volcanic edifice only 10-45 minutes before the paroxysms-too short for organized evacuations but potentially enough time for automated warning systems to alert people in the immediate danger zones.

Data interpretation challenges 🔗

Another significant challenge lies in interpreting complex, multi-parameter datasets. Different monitoring techniques sometimes provide conflicting signals, and distinguishing between normal volcanic fluctuations and true precursors to dangerous eruptions requires experience, judgment, and often some element of uncertainty. The scientific understanding of volcanic processes continues to evolve, meaning monitoring strategies must adapt accordingly.

Looking ahead: innovations in volcanic surveillance 🔗

Italian volcano monitoring continues to advance. New technologies like distributed acoustic sensing using fiber-optic cables, machine learning algorithms for automatic event detection, and improved satellite systems promise to enhance surveillance capabilities. The integration of these tools with traditional monitoring networks will likely improve both the detection of volcanic unrest and the forecasting of potentially dangerous eruptions.

The ultimate goal remains clear: providing enough advance warning to protect lives while maintaining the scientific rigor needed to avoid unnecessary evacuations that can devastate local economies. In volcanic areas like Stromboli and Vulcano, where tourism forms a crucial economic pillar, finding this balance between safety and livelihood represents an ongoing challenge that sophisticated monitoring helps to address.

What do you think? How much advance warning would you want before a volcanic eruption if you lived near an active volcano? And knowing that some dangerous eruptions can occur with little warning, would you still choose to live on these beautiful but risky volcanic islands?

References

1. https://www.nature.com/articles/s41467-021-24420-1
2. https://link.springer.com/article/10.1007/s00445-025-01810-7
3. https://rischi.protezionecivile.gov.it/en/volcanic/volcanoes-italy/stromboli/
4. https://www.mdpi.com/2072-4292/14/5/1283