Mount Etna

Simplified geological cross section of the Mt. Etna volcanic complex (not to scale), showing its evolution from an early stage of submarine fissural activity, producing pillow lavas and a first shield volcano, to a subsequent mixed effusive and explosive activity building three main stratovolcano stages (Monte Calanna; Trifoglietto 1; Trifoglietto 2), then to the present Mongibello system (which has developed in two successive stages from about 15,000 years ago). The volcanic activity has gradually shifted from SE to NW (from offshore to onshore). The Valle del Bove is a huge collapse of the eastern flank of the volcano, that occurred about 64,000 years ago, now allowing the older volcanic edifices to be recognized.

Mount Etna from the south with the smoking peak in the upper left and a lateral crater in the centre

Volcanic activity first took place at Etna about 500,000 years ago, with eruptions occurring beneath the sea off the ancient coastline of Sicily.[18] About 300,000 years ago, volcanism began occurring to the southwest of the summit (centre top of the volcano), then activity moved towards the present centre 170,000 years ago. Eruptions at this time built up the first major volcanic edifice, forming a stratovolcano in alternating explosive and effusive eruptions. The growth of the mountain was occasionally interrupted by major eruptions, leading to the collapse of the summit to form calderas.

From about 35,000 to 15,000 years ago, Etna experienced some highly explosive eruptions, generating large pyroclastic flows, which left extensive ignimbrite deposits. Ash from these eruptions has been found as far away as south of Rome's border, 800 km (497 mi) to the north.

Thousands of years ago, the eastern flank of the mountain experienced a catastrophic collapse, generating an enormous landslide in an event similar to that seen in the 1980 eruption of Mount St. Helens. The landslide left a large depression in the side of the volcano, known as 'Valle del Bove' (Valley of the Ox). Research published in 2006 suggested this occurred around 8,000 years ago, and caused a huge tsunami, which left its mark in several places in the eastern Mediterranean.[19]

The steep walls of the valley have suffered subsequent collapses on numerous occasions. The strata exposed in the valley walls provide an important and easily accessible record of Etna's eruptive history.

The most recent collapse event at the summit of Etna is thought to have occurred about 2,000 years ago, forming what is known as the Piano Caldera. This caldera has been almost entirely filled by subsequent lava eruptions but is still visible as a distinct break in the slope of the mountain near the base of the present-day summit cone.

Mount Etna is moving towards the Mediterranean Sea at an average rate of 14 mm (0.55 in) per year, the massif sliding on an unconsolidated layer above the older sloping terrain.[20][21]

The first known record of eruption at Etna is that of Diodorus Siculus.[22]

An artist's impression of the 1766 eruption

In 396 BCE, an eruption of Etna reportedly thwarted the Carthaginians in their attempt to advance on Syracuse during the Second Sicilian War.

A particularly violent explosive (Plinian) summit eruption occurred in 122 BCE, and caused heavy tephra falls to the southeast, including the town of Catania, where many roofs collapsed.[23] To help with reconstruction after the devastating effects of the eruption, the Roman government exempted the population of Catania from paying taxes for ten years.

The Roman poet Virgil gave what was probably a first-hand description of an eruption in the Aeneid.[24]

During the first 1500 years CE, many eruptions went unrecorded (or records have been lost); among the more significant are: (1) an eruption in about 1030 CE near Monte Ilice on the lower southeast flank, which produced a lava flow that travelled about 10 km, reaching the sea north of Acireale; the villages of Santa Tecla and Stazzo are built on the broad delta built by this lava flow into the sea; (2) an eruption in about 1160 (or 1224), from a fissure at only 350–450 m (1,148–1,476 ft) elevation on the south-southeast flank near the village of Mascalucia, whose lava flow reached the sea just to the north of Catania, in the area now occupied by the portion of the city named Ognina.

Rabban Bar Sauma, a Chinese traveller to the West, recorded the eruption of Etna on 18 June 1287.[25]

The 1669 eruption, Etna's most destructive since 122 BCE, started on 11 March 1669 and produced lava flows that destroyed at least 10 villages on its southern flank before reaching the city walls of the town of Catania five weeks later, on 15 April. The lava was largely diverted by these walls into the sea to the south of the city, filling the harbour of Catania. A small portion of lava eventually broke through a fragile section of the city walls on the western side of Catania and destroyed a few buildings before stopping in the rear of the Benedictine monastery, without reaching the centre of the town. Contrary to widespread reports of up to 15,000 (or even 20,000) human fatalities caused by the lava,[26] contemporaneous accounts written both in Italian and English[27] mention no deaths related to the 1669 eruption (but give very precise figures of the number of buildings destroyed, the area of cultivated land lost, and the economic damage). Therefore, it is uncertain where the enormous number of fatalities can be attributed. One possibility is confusion between this eruption and an earthquake that devastated southeast Sicily (including Catania) 24 years later in 1693. A study on the damage and fatalities caused by eruptions of Etna in historical times reveals that only 77 human deaths are attributable with certainty to eruptions of Etna, most recently in 1987 when two tourists were killed by a sudden explosion near the summit.[28][29]

Since 1750, seven of Etna's eruptions have had durations of more than 5 years, more than any other volcano except Vesuvius.[30]

As "Europe's most active volcano,"[31] eruptions occur frequently (with as many as 16 eruptions taking place in 2001).[31] However, several eruptions of note have occurred over the last century.

A major eruption took place in June 1923, lasting from June 6 until June 29.[32] A large lava flow from an eruption in 1928 led to the destruction of a population centre for the first time since the 1669 eruption. The eruption started high on Etna's northeast flank on 2 November. Then new eruptive fissures opened at decreasing elevations down the flank of the volcano. The third and most vigorous of these fissures opened late on 4 November at an unusually low elevation, approximately 1,200 m (3,937 ft) above sea-level, in a zone known as Ripe della Naca. The village of Mascali, lying down-slope of the Ripe della Naca, was almost completely destroyed in two days. Only a church and a few surrounding buildings survived in the north part of the village, called Sant'Antonino or "il quartiere". During the last days of the eruption, the flow interrupted the Messina-Catania railway line and destroyed the train station of Mascali. The event was used by Benito Mussolini's fascist regime for propaganda purposes, with the evacuation, aid, and rebuilding operations being presented as models of fascist planning. Mascali was rebuilt on a new site, and its church contains the Italian fascist symbol of the torch, placed above the statue of Jesus Christ.[33]

Etna's 2002 eruption, photographed from the ISS

Long exposure image of a "dual-vent" eruption from Mount Etna's NSEC (New South East Crater)

Other major 20th-century eruptions occurred in 1949, 1971, 1979, 1981, 1983 and 1991–1993. In 1971, lava buried the Etna Observatory (built in the late 19th century), destroyed the first generation of the Etna cable-car, and seriously threatened several small villages on Etna's east flank. In March 1981, the town of Randazzo on the northwestern flank of Etna narrowly escaped destruction by unusually fast-moving lava flows. That eruption was remarkably similar to one in 1928 that destroyed Mascali. The 1991–1993 eruption saw the town of Zafferana threatened by a lava flow, but successful diversion efforts saved the town with the loss of only one building a few hundred metres from the town's margin. Initially, such efforts consisted of the construction of earth barriers built perpendicularly to the flow direction; it was hoped that the eruption would stop before the artificial basins created behind the barriers would be completely filled. Instead, the eruption continued, and lava surmounted the barriers, heading directly toward Zafferana. Engineers then decided to use explosives near the source of the lava flow, to disrupt a very efficient lava tube system through which the lava travelled for up to 7 km (4 mi) without losing significant heat or fluidity. The main explosion on 23 May 1992 destroyed the tube and forced the lava into a new artificial channel, far from Zafferana, and it would have taken months to re-establish a long lava tube. Shortly after the blasting, the rate of lava emission dropped, and during the remainder of the eruption (until 30 March 1993) the lava never advanced close to the town again.[34]

A lateral crater of the 2002–2003 eruption near the Torre del Filosofo, about 450 m (1,480 ft) below Etna's summit

House destroyed by lava on the slopes of Etna

Following six years (1995–2001) of unusually intense activity at the four summit craters of Etna, the volcano produced its first flank eruption since 1991–1993 in July–August 2001. This eruption, which involved activity from seven distinct eruptive fissures mostly on the south slope of the volcano, was well covered by the mass-media because it occurred at the height of the tourist season and numerous reporters and journalists were already in Italy to cover the G8 summit in Genoa. It also occurred close to one of the tourist areas on the volcano, and thus was easily accessible. Part of the "Etna Sud" tourist area, including the arrival station of the Etna cable car, were damaged by this eruption, which otherwise was a rather modest-sized event by Etna standards.

In 2002–2003, a much larger eruption threw up a huge column of ash that could easily be seen from space and fell as far away as Libya, 600 km (370 mi) south across the Mediterranean Sea. Seismic activity in this eruption caused the eastern flanks of the volcano to slip by up to two metres, and many houses on the flanks of the volcano experienced structural damage. The eruption also completely destroyed the tourist station Piano Provenzana, on the northeastern flank of the volcano, and part of the tourist station "Etna Sud" around the Rifugio Sapienza on the south flank. Footage from the eruptions was recorded by Lucasfilm and integrated into the landscape of the planet Mustafar in the 2005 film Star Wars: Episode III – Revenge of the Sith.[35] The Rifugio Sapienza is near the site of a cable car station which had previously been destroyed in the 1983 eruption; it has now been rebuilt. Following a slow and non-destructive lava outflow on the upper southeastern flank between September 2004 and March 2005, intense eruptions occurred at the Southeast Crater in July–December 2006. These were followed by four episodes of lava fountaining, again at the Southeast Crater, on 29 March, 11 April, 29 April and 7 May 2007. Ash emissions and Strombolian explosions started from a vent on the eastern side of the Southeast Crater in mid-August 2007.

On 4 September 2007, a major episode of lava fountaining occurred from the new vent on the east side of the Southeast Crater, also producing a plume of ash and scoriae which fell over the east flank of the volcano. A lava flow travelled about 4.5 km (2.8 mi) into the uninhabited Valle del Bove. This eruption was visible far into the plains of Sicily, ending the following morning between the hours of 5 to 7 a.m. local time. Catania-Fontanarossa Airport shut down operations during the night for safety precautions.

An eruption on the morning of 13 May 2008, immediately to the east of Etna's summit craters was accompanied by a swarm of more than 200 earthquakes and significant ground deformation in the summit area. The eruption continued at a slowly diminishing rate for 417 days, until 6 July 2009, making this the longest flank eruption of Etna since the 1991–1993 eruption that lasted 473 days. Previous eruptions, in 2001, 2002–2003, and 2004–2005 had lasted 3 weeks, 3 months, and 6 months, respectively. Lava flows advanced 6.5 km during the first few days of this eruption but thereafter stagnated at many minor distances from the vents; during the last months of the eruption lava rarely advanced more than 1 km downslope.

Southern flank of Mount Etna showing lateral cones and flow from the eruption of 2001.

Through January 2011 to February 2012, the summit craters of Etna were the site of intense activity. Frequent eruptions and ash columns forced the authorities to shut down the Catania airport on several occasions. [36][37][38][39][40][41] The July 2011 episode also endangered the Sapienza Refuge, the main tourist hub on the volcano, but the lava flow was successfully diverted. In 2014, a flank eruption started involving lava flows and strombolian eruptions. This was the first flank eruption since 2008–09.[42]

On 3 December 2015, an eruption occurred which climaxed between 03:20 and 04:10 local time. The Voragine crater exhibited a lava fountain which reached 1 km (3,300 ft) in height, with an ash plume which reached 3 km (9,800 ft) in height.[43][44] The activity continued on the following days, with an ash plume that reached 7 km (23,000 ft) in height that forced Catania airport to shut down for a few hours.[45] Volcanic gas emissions from this volcano are measured by a multi-component gas analyzer system, which detects pre-eruptive degassing of rising magmas, improving prediction of volcanic activity.[46]

An eruption on 16 March 2017 injured 10 people, including a BBC News television crew, after magma exploded upon contact with snow.[47][48]

An eruption on 24 December 2018, following a dyke intrusion at shallow depth, spewed ash into the air, forcing the closure of airspace around Mount Etna. Two days later, a magnitude 4.9 earthquake shook the town of Fleri and surrounding towns and hamlets in the Province of Catania, damaging buildings and injuring four people.[49][50]

Beginning in February 2021, Mount Etna began a series of explosive eruptions, which have had an impact on nearby villages and cities, with volcanic ash and rock falling as far away as Catania. As of 12 March 2021, the volcano has erupted 11 times in three weeks.[51] The eruptions have consistently sent ash clouds over 10 km (33,000 ft) into the air, closing Sicilian airports. There have been no reports of injuries.

In February 2022 there were two eruptions. On 11 February 2022, at 6 pm, there were lava fountains from the Southeast Crater which became a single Strombolian eruption by 7 pm. Between 10 and 11 pm it had reached a height of almost 1,000 m and lava bombs were thrown at a considerable distance. Ash was blown west by the wind and then turned southeast. There was large lava flow in the western flank. On 19 February at 10.15 am there was an explosive eruption, again from the Southeast Crater, high lava fountains and lava flows, the longest of which went down the north-eastern flank towards the Bove Valley. [52][53][54]

On 29 May 2022 a sudden collapse of the Southeast Crater created a fracture on its northern flank at an elevation of circa 2,800 m (9,186 ft). A small lava flow emerged and headed in the direction of the Leone Valley, just above the much larger Bove Valley. It continued for three days and was accompanied by small and sporadic eruptions from two of the many vents at the top of this crater.[55][56]

The Global Volcanism Program has assigned a Volcanic Explosivity Index (VEI) to all of Mount Etna's eruptions since January 1955:[57]

Smoke ring above Mount Etna observed on 9^th August 2023

Map of municipalities in the province of Catania (Mount Etna at top right)

In the 1970s Etna erupted smoke rings,[58] one of the first recorded events of this type, which are extremely rare. This happened again in 2000.[59] Video footage of 8 June 2000 event was captured.[60][61] Another event occurred on 11 April 2013.[62] Other similar events occurred during the summer of 2023 (see photo).