Mount Etna is the highest active volcano in Europe. It is located on the east coast of Sicily, Italy, above a subduction zone formed where the Eurasian and African plate boundaries collide.
Etna’s highest elevation is about 10,900 feet. Like other active volcanoes, it varies in height, increasing during eruptions and decreasing from the periodic collapse of the rim. In 1865, the volcano’s summit was about 170 feet higher than it was in the early 21st century. Etna’s base is about 22 miles in diameter.
Mount Etna is a series of nested stratovolcanoes with four distinct summit craters. Stratovolcanoes are characterized by a steep profile and more violent eruptions.
The mountain has three ecological zones. The lowest zone, sloping gradually upward to about 3,000 feet, is fertile and rich in vineyards, olive groves, citrus plantations and orchards. Several densely populated areas, including the city of Catania, are found on the lower slopes, but settlements become less frequent as the height increases. In the next zone, the mountain grows steeper and is covered with forests. At heights of more than 6,500 feet, the mountain is covered with ashes, sand and fragments of lava.
While there are hazards of living near an active volcano, many villages have developed on the slopes of Mount Etna. Today, more than 25% of Sicily’s population lives on the mountain. The frequent eruptions and lava flow are largely contained to its uninhabited slopes, so it rarely poses a danger to its residents.
Etna is the main source of income for Sicily, both from agriculture and tourism. The eruptions have made the surrounding soil fertile, allowing locals to grow olives, grapes and fruit. Tourism is high as visitors come to ski, hike or visit the mountain during an eruption.
Diverting the lava path
Etna, however, has been dangerous and even deadly in the past. The town of Catania lies at the base of the mountain and was affected by Etna’s worst-known eruption. There have been attempts to control the path of lava flows that are a threat to the city.
The first attempt was in 1669. Workers dug a trench above Catania to try to divert the lava stream. However, residents of a nearby village realized the new flow direction could affect them, instead. They fought the Catanians, and the lava breach hardened and filled again.
In 1992, there was another attempt to divert the lava. The U.S. Marines worked with Italian volcanologists and used explosives to blast a hole in a lava tunnel. Then, they dropped large blocks of concrete into the hole to try to stop the flow. While this slowed the progression of the lava, it didn’t stop it.
The Volcanic Explosivity Index (VEI) is a scale that measures the explosivity of historic eruptions.
The VEI level is primarily determined by the volume of products expelled. The eruption cloud height and the duration of the eruption are used to determine the explosivity value.
The scale is logarithmic, with each interval increasing by 10 times. A value of 0 is given for nonexplosive eruptions. The largest volcanic eruptions in history were given magnitude 8.
On March 11, 1669, an eruption began on Mount Etna that would become the volcano’s most violent eruption in history. The event lasted until July 1669.
The eruption took place along a fissure that opened and widened into a chasm from which lava flowed. This formed a double cone more than 150 feet high that was named Monti Rossi.
During the event, about 990 million cubic yards of lava were thrown out, destroying a dozen villages on the lower slope and submerging the western part of the town of Catania. The ash was sent out as far as 100 miles away to mainland Italy.
Catania workers had made an attempt to divert the lava flow away from the city, but were unsuccessful.
Catania residents failed to evacuate, apparently believing the lava would stop or the city’s defensive walls would protect them. Neither was the case, and much of the city was destroyed.
Approximately 3,000 people living on the slopes of the mountain died from asphyxiation, and about 17,000 people in Catania died after failing to leave the city. About 27,000 people were left homeless.
Mount Etna is the most active volcano in Europe and the second-most active volcano in the world, behind Kilauea in Hawaii.
Etna’s geologic history shows that it has been nearly continuously active for thousands of years. Etna has one of the world’s longest documented records of historical volcanism, dating to approximately 1500 B.C.
Since then, the volcano has erupted around 200 times, though most were moderately small.
Etna has experienced a variety of eruption styles, but two types of activity typically occur. The first type of activity is explosive eruptions from one or more of the summit craters. Minor lava emissions sometimes occur with these vertical eruptions. This activity is almost continuous but poses little threat to inhabitants.
The second type of activity is flank eruptions. These eruptions are less frequent but cause more damage as they originate from vents and fissures that can open at much lower, inhabited elevations.
Major recorded eruptions can be found throughout the volcano’s history. Some of them include:
A large eruption in 122 B.C. caused widespread damage to Catania. Roman taxes were canceled for 10 years to help locals rebuild.
An ancient eruption in 396 B.C. kept the Carthaginian army from reaching Catania.
Catania was also in the path of destruction in 1669. That year, Etna saw its most violent recorded eruption in history.
In 1787, lava fountains were reportedly 9,842 feet high.
An extremely violent eruption in 1852 produced more than 2 billion cubic feet of lava and nearly destroyed the town of Zafferana.
In 1928, a fissure opened up near the foot of the mountain and cut off the railway. The village of Mascali was buried in only two days.
Etna’s longest recorded eruption began in 1979 and went on for 13 years.
In the early 21st century, a major eruption began in July 2001 and lasted several weeks.
On Feb. 16, Etna erupted, sending lava down the mountain’s eastern slope toward the uninhabited Bove Valley. The volcano has also sent out ash and lava stones down the southern side.
The activity has been continuing since, in bursts more or less intense. At times, lava fountains soared as high as 4,792 feet above Etna’s summit — roughly three times the height of One World Trade Center, the tallest building in the U.S.
Volcanologists at the Etna Observatory say there’s no way of predicting how long this round of activity will last. No injuries or serious damage have been reported.