Mount Etna

Etna started as a lower, flatter volcano.

Then eruptions piled up layer after layer of lava and ash. The mountain grew taller and taller. Big hollows formed when parts of it fell in.

Etna has been growing for a very long time. UNESCO says its eruptive history goes back 500,000 years. The Smithsonian explains that today's tall cone, called Mongibello, was built on top of an older, flatter shield volcano. Layer after layer of lava and ash made it grow, the way all stratovolcanoes do.

Etna has more than one place where lava comes out. Besides its summit craters, cracks called fissures open on its sides, and small cinder cones grow around them. On its eastern side is the Valle del Bove, a huge hollow about 5 by 10 kilometers, which the Smithsonian describes as a caldera, a basin formed when part of a volcano collapses.

The Global Volcanism Program describes the Mongibello stratovolcano, truncated by several small calderas, as built during the late Pleistocene and Holocene over an older shield volcano; its most prominent feature is the Valle del Bove, a 5 by 10 km caldera open to the east. UNESCO traces Etna's eruptive history back 500,000 years, while Britannica dates its activity from the end of the Neogene, about 2.6 million years ago, and notes that the present structure reflects at least two main eruptive centers.

Two styles of eruption typically occur, sometimes together: persistent explosive activity, with minor lava, from one or more summit craters; and less frequent flank eruptions with higher effusion rates from fissures that open progressively downslope from near the summit, usually with Strombolian activity at their upper end. Cinder cones commonly form over lower-flank vents. Britannica describes Strombolian eruptions as moderate bursts of expanding gas that throw out clots of glowing lava in cyclical or nearly continuous small eruptions.

People have watched Etna erupt for thousands of years.

Sometimes lava flows slowly down its sides. Long ago, lava reached the sea. Etna still erupts often, so scientists keep watch.

Etna has one of the longest written records of any volcano. The Smithsonian says records go back to 1500 BCE, and UNESCO says at least 2,700 years of eruptions have been described by people. Writers in ancient Greece mentioned a famous eruption in 475 BCE.

The most violent eruption in its recorded history, Britannica says, was in 1669, when a crack opened above the town of Nicolosi and lava flowed for four months, reaching the city of Catania. Workers dug a trench to try to turn the lava aside, which Britannica says seems to have been the first attempt ever made to divert lava. Etna still erupts often. In 1983 people used explosives to try to divert a lava flow, and on 2 June 2025 an eruption sent an ash cloud about 6,400 meters into the sky.

Britannica counts 71 recorded eruptions between 1500 BCE and 1669 CE, 14 of them before the Common Era; Pindar and Aeschylus referred to a famous eruption of 475 BCE, and in 1381 a lava flow reached the Ionian Sea about 16 km away. The most violent historical eruption, from 11 March to 15 July 1669, poured out about 830 million m³ of lava from a fissure above Nicolosi, built the 46 m double cone of Monti Rossi, destroyed a dozen villages and reached the western part of Catania; a trench dug to divert the flow is, historically, the first known attempt to divert lava.

Twenty-six more eruptions were reported from 1669 to 1900; the 20th century brought eruptions in 1908, 1910, 1911, 1918, 1923, 1928 (which cut the railway and buried Mascali), 1942, 1947, 1949, 1950-51 and 1971, with near-continuous activity afterward, dynamite used to divert lava in 1983, and major eruptions in 1986 and 1999. Since 2001, Strombolian episodes have recurred; on 2 June 2025 an eruption raised a volcanic cloud to about 6,400 m, triggering a red alert for aircraft and disrupting tourist visits.

Scientists watch Etna all day, every day.

Cameras look at the craters. Machines feel the ground shake. When Etna gets busy, scientists warn people and airplanes.

Etna has been studied carefully since the middle of the 1800s, and UNESCO calls it one of the best-studied and best-watched volcanoes in the world. More than 50 small seismic stations, which feel the ground shaking, sit inside the World Heritage area, along with a scientific observatory.

Scientists of Italy's National Institute of Geophysics and Volcanology (INGV), at their Etna Observatory in Catania, use surveillance cameras, earthquake and tremor sensors, and instruments that measure how the ground swells. They send updates to Italy's Civil Protection Department whenever activity changes, including forecasts of where an ash cloud might drift.

Britannica dates systematic study of Etna to the mid-19th century, with observatories set up at Catania, Casa Etnea and Cantoniera. UNESCO describes it as one of the best-studied and monitored volcanoes in the world, with over 50 small seismic monitoring stations and a scientific observatory inside the property, and says its almost continuous activity continues to shape volcanology and geophysics.

The INGV Osservatorio Etneo issues communiqués to the Civil Protection Department. A typical one, from 15 July 2024, reported continuing Strombolian activity at the Voragine crater seen by surveillance cameras, weak ash emission from the Northeast Crater, a forecast of the ash plume's direction, rising volcanic tremor with its source located near the Southeast Crater about 2,500 m above sea level, lively infrasound, and no significant changes in tilt, GNSS or strain networks.

The top of Etna can be dangerous when it erupts.

Sometimes visitors are not allowed near the top. Go with a guide and a grown-up. Wear strong shoes and warm clothes.

Because Etna is so active, the towns around it issue rules about how high visitors may go. The Etna Park explains that these rules change with the volcano's activity: sometimes people may hike freely up to a certain height, and higher up only with a guide. Visitors must wear proper safety equipment.

UNESCO notes that the top of the volcano may be closed to the public for safety reasons, and Britannica reports that the eruption of June 2025 disrupted tourist visits. Before going, check the current rules, go with an authorized guide, and stay with your group. Inside the World Heritage area, dogs are not allowed and organized activities such as mountain biking need permission.

The Parco dell'Etna explains that municipal ordinances limit access to the summit zone according to the volcanic risk at the time, under national civil protection law and the regional alert procedures: they set the heights up to which free excursions are allowed and above which visitors must be accompanied by guides, and they require safety equipment as described in the regional procedures for the summit zone. In summer 2026, the park listed current ordinances from Adrano, Belpasso, Bronte, Maletto, Milo and Sant'Alfio.

UNESCO records that public access to the summit may be officially prohibited for safety reasons, that vehicle access is restricted to authorized purposes such as organized 4x4 drives toward the INGV observatory, that recreational activities like mountain biking or riding need advance authorization, and that dogs are not allowed. Britannica notes that the 2 June 2025 eruption triggered a red alert for aircraft and disrupted tourist visits, a reminder that conditions can change quickly.