1669 eruption of Mount Etna
The 1669 eruption of Mount Etna is the largest-recorded historical eruption of the volcano on the east coast of Sicily, Italy. After several weeks of increasing seismic activity that damaged the town of Nicolosi and other settlements, an eruption fissure opened on the southeastern flank of Etna during the night of 10–11 March. Several more fissures became active during 11 March, erupting pyroclastics and tephra that fell over Sicily and accumulated to form the Monti Rossi scoria cone.
Lava disgorged from the eruption fissures flowed southwards away from the vent, burying a number of towns and farmland during March and April, eventually covering 37–40 square kilometres (14–15 sq mi). The inhabitants of the towns fled to the city of Catania and sought refuge there; religious ceremonies were held in the city to implore the end of the eruption. In early April a branch of the lava flow advanced towards the city and on the 1 or 16 April it reached its city walls, provoking a crisis and the flight of many of its inhabitants. The city walls held up the lava, which began to flow into the Ionian Sea. More than two weeks later, parts of the flow surmounted the walls and penetrated Catania but did not cause much damage. The eruption ended in July.
The first recorded attempt to divert a lava flow occurred when priest Diego Pappalardo and fifty others worked to break up a lava flow in an effort to divert it. The effort was initially successful but the diverted flow threatened another town whose inhabitants chased Pappalardo and his men away and the lava flow resumed its original course towards Catania. There are no known fatalities of the 1669 eruption but many towns, parts of Catania and farmland were destroyed by the lava flow and the earthquakes that accompanied the eruption. News of the eruption spread as far as North America and a number of contemporaries described the event, leading to an increased interest in Etna's volcanic activity.
Context[edit]
Mount Etna lies on the island of Sicily, at the coast facing the Ionian Sea.[3] Etna is one of the most iconic and active volcanoes in the world; its eruptions–including both effusive and explosive eruptions from flank and central vents–have been recorded for 2,700 years.[4][5] Etna had been unusually active during the 17th century, with several long lasting and voluminous eruptions[6] and volcanic activity also increased on Vulcanello in the Aeolian Islands; a similar concordance between activity at Etna and in the Aeolian Islands was also observed in 2002.[7] During the two months before the 1669 eruption, the output of gas and steam from Etna's summit craters had been higher than usual.[8]
In 1669, Sicily was part of the Kingdom of Aragon, which governed the island through a viceroy in Palermo.[9] A highly productive agricultural sector existed on the heavily urbanized southeastern slopes of Etna;[10] settlements had grown there during the High Middle Ages.[3] Catania had a population of about 27,000 and was the third-largest city of the Kingdom of Naples and Sicily.[11]
Events[edit]
Prelude[edit]
Seismic activity at Mount Etna began on 25 February 1669[1][12] and increased over the next two weeks.[13] It reached its zenith during the night of 10 and 11 March when earthquakes destroyed Nicolosi.[14] The seismic activity caused damage in Gravina, Mascalucia, Pedara and Trecastagni,[15] and was felt as far away as Catania.[1] A number of seismic events are reported in contemporaneous records but their timing and frequency are not known.[16] Early activity that lasted until 9 March reflects the ascent of deep magma within the mountain while subsequent earthquakes were associated with the opening of the eruption fissure. These early events impacted a wider area than the later ones;[16] earthquake activity diminished after the eruption had begun.[17]
Eruption commences and events at the vent[edit]
After midnight on 11 March, the first fissure opened up on Etna[1] between the Monte Frumento Supino cinder cone[18] and Piano San Leo.[19] This 2-meter (6.6 ft) wide and 9-kilometer (5.6 mi) long fissure between 2,800–1,200 m (9,200–3,900 ft) elevation was accompanied by weak eruptive activity at its upper end[13] and an intense glow on its lower end. During the afternoon of the same day, a second fissure opened and erupted lithics and ash clouds; historical records vary on the number of vents that became active.[1] An alternative reconstruction of events envisages the development of several fissure segments between 950–700 m (3,120–2,300 ft) elevation, most of which underwent brief explosive and effusive eruptions.[20] At 18:30, the main vent became active and lava began to flow from the second fissure[13] from east of the Monte Salazara cone,[1] close to Nicolosi,[21] at 800–850 m (2,620–2,790 ft) elevation[13] in Etna's southern rift zone.[22]
A fifth fissure segment south of the Monpilieri cinder cone was briefly active on 12 March[20] and several vents – sources disagree on the exact number – became active on 12 March around the main vent with lava fountaining.[1] The Monti Rossi cinder cone developed over the main vent and was almost fully formed by 13 March.[1]
Explosive eruption[edit]
An eruption column rose from the vent and deposited tephra,[14] pyroclastics covered large parts of Etna's southeastern flank[23] and ash from the eruption traveled as far as Calabria and Greece.[24] Strombolian and lava fountaining took place, generating pyroclastics[25] including lapilli and lava bombs,[1] which fell over the southeastern flank for three months.[26] These deposits reached a thickness of 12 centimetres (4.7 in) 5 km (3.1 mi) from the vent;[27] roofs in Acireale,[1] Pedara, Trecastagni and Viagrande collapsed under the weight of the tephra.[14] Huge boulders were ejected to distances of several kilometers.[28] Most of the tephra was produced within the first few days of the eruption.[29]
The explosive stages of the 1669 eruption produced 0.066 km3 (0.016 cu mi) of pyroclastics[14] and have been classified as category 2–3 on the Volcanic Explosivity Index, making it one of the most intense eruptions of Etna.[2] Subplinian eruptions on Etna's flanks are not common; other examples are the prehistoric eruptions of Monte Moio[30] 28,600 ± 4,700 years ago,[25] Monte Frumento delle Concazze 3,500 years ago and Monte Salto del Cane 3,000 years ago.[30]
Over three million tons of sulfur were released by the eruption. This sulfur may have risen into the upper troposphere, causing changes in the chemistry of the regional atmosphere and environmental hazards.[31] The 1669 eruption, however, did not form a substantial atmospheric dust veil.[32]
Lava flow[edit]
Lava now flowed out of the volcano into a densely populated area[19] at an average rate of 50–100 m3/s (1,800–3,500 cu ft/s),[13] with a peak rate of 640 m3/s (23,000 cu ft/s).[33] Lava emanating from the vent flowed around the Mompilieri[14][34]/Monpilieri cinder cone and during 12 March destroyed the village of Malpasso.[35] The town of Mompilieri fell victim to the lava flows during the night[20] and Mascalucia was covered the day after.[35] During and after 14 March, the lava flow branched out in three directions and began to advance southwards;[35] the western branch destroyed villages close to Mascalucia, and houses around Camporotondo and San Pietro.[20]
Response[edit]
When the eruption began to destroy settlements and land north of Catania, the people fled to the city. Authorities in Catania requested assistance from the then-viceroy of Sicily Francisco Fernández de la Cueva, 8th Duke of Alburquerque and took care of about 20,000 refugees.[54] These refugees sought out the city as a safe haven because it was distant from the eruption at that time and they were received with great hospitality. It appears that during this time, religious ceremonies took up much of the daily lives of Catania's populace.[55]
As the eruption continued and lava flows advanced towards Catania,[55] law and order broke down, panic ensued – an unusual event during a natural disaster – and the authorities of Catania were overwhelmed. The viceroy appointed Prince Stefano Riggio as vicar-general to manage the crisis[11][56] per l'incendio di Mongibello ("for the fire of the Mongibello"); Riggio arrived on 18 April and found a largely depopulated city as the artisanal class and the aristocracy had fled Catania and others had followed in their wake. Riggio prepared barracks north of Catania to take up refugees and evacuated both prisons, the city archives,[57] food reserves and religious objects from the city.[14] When lava broke over the city walls on 30 April,[57] the evacuation of the city was considered but then rejected. Instead, the walls threatened by the lava flows were reinforced, gates blocked and when the lava penetrated them restraining walls[11] and barriers were built from the debris of destroyed houses.[58][c] The viceroy later sent also money for recovery.[60]
Eruptions of Etna were interpreted as the consequence of divine wrath and suffering being inflicted on the sinful people. Religious services took place in Catania and other villages; during processions the relics of St. Agatha, the Martyr of Catania, were carried around and people flagellated themselves.[61][54] Some sources suggest the veil of St. Agatha spared the city from total destruction.[62]
Fifty inhabitants of Pedara led by priest Diego Pappalardo[11] attempted to divert a lava flow by breaking up the margins with axes and picks while protecting themselves from the heat through water-soaked hides. This effort worked initially until 500 inhabitants of Paternò put a stop to it because their town was threatened by the redirected lava flow.[59][63] The diversion attempt failed when the breach healed.[63] This effort constitutes the first recorded attempt at changing the course of a lava flow.[11][64] As a consequence of the incident between Paterno and the people attempting the diversion, it was declared and formally ratified in the 19th century that people diverting a lava flow would be liable for the damage caused by it; this rule was only suspended during the eruption of 1983[63] although clandestine attempts, sometimes with official backing, had occurred before that year.[65] There were religious objections to diverting lava flows; such an intervention was viewed as sacrilegious in the context of the relationship between God, man, and nature.[66]
Impact[edit]
On the volcano[edit]
The 1669 eruption is considered to be the most important historical flank eruption of Etna.[53] With a volume of 0.5–1 km3 (0.12–0.24 cu mi)[d] lava,[13] the 1669 eruption is Etna's largest during the last 400 years[4] and its largest historical effusive eruption.[67] Its lava field is the largest in the volcano's history[4][31] and the longest flow at Etna during the last 15,000 years.[33]
The lava flow of 1669 covered an area of 37 km2 (14 sq mi)[35]-40 km2 (15 sq mi),[4][e] radically changing the morphology of the volcano.[21] It is considered an aa lava field[59] that also contains "toothpaste" lava with tabular and plate-like structures of varying sizes[69] and numerous lava channels.[70] The lava extended the coast by 800 m (2,600 ft) over a width of 1.5 km (0.93 mi).[14] An older volcanic cone[71] and lava flows from earlier eruptions were partially buried.[72][73]
The 1669 eruption came at the end of a period of high effusive activity that began in 1610.[3] The behavior of Etna changed after the eruption,[13] presumably due to the large volume of material erupted in the 1669 event and changes in the plumbing system it caused.[74] After 1669, Etna's eruptions were smaller, shorter, and more sporadic[13] with fewer flank eruptions,[74][f] and mafic phenocrysts became more common in the lavas.[13] The 1669 eruption has been defined as the starting point of a century-long cycle of activity that continues to this day[76] and Etna's volcanic products are subdivided into pre-1669 and post-1669 formations in Italy's geological map.[77]
Geology[edit]
The lavas erupted in 1669 define a sodic hawaiite suite[117][k] with two distinct acidic and mafic members[74] that were erupted before and after 20 March, respectively. These two magmas formed through fractional crystallization processes in different parts of Mount Etna's plumbing system.[118] It appears that prior to the 1669 eruption, a batch of more acidic magma was residing underneath Etna. A batch of new, more mafic magma that was more buoyant than the residing magma penetrated and traversed the magmatic system, and reached the surface. Later, the more acidic magma erupted.[74][118] Magma was accumulating prior to 1669 in the plumbing of Mount Etna;[119] increased volatile content or increased magma volume might have eventually triggered the eruption.[120]
The lava flows of 1669 contain up to 18% bubbles, a large proportion and considerably more than expected from lava flows on the surface that might explain the fluidity of the flows that maintained pahoehoe morphology 16 km (9.9 mi) from the vents.[121] The lava also contains large phenocrysts of plagioclase, as do lavas of other eruptions of the 17th century; these lavas are called cicirara[122] and they often appear at the end of an eruption cycle at Mount Etna.[6]
Research history[edit]
Owing to its magnitude, the eruption was well documented by contemporaries.[13] Records range from administrative documents that were part of the crisis management and the post-crisis management over memoirs to eyewitness reports.[123] Italian scientist Giovanni Alfonso Borelli (1608–1679) in his 1670 publication Historia et Meteorologia and the British ambassador in Constantinople Heneage Finch, 3rd Earl of Winchilsea (1628–1689) in a report to King Charles II of England[l] wrote about the eruption. Later reviews of the eruption were written by the British diplomat Sir William Hamilton (1730–1803).[38] Borelli's history of the 1669 eruption is the oldest scientific description of Etna's volcanic activity.[124] Anonymous reports published in 1669 include An answer to some inquiries concerning the eruptions of Mt. Aetna, 1669, communicated by some inquisitive merchants now residing in Sicily and A chronological account of several Incendiums or fires of Mt. Aetna.[38] The large number of contemporary records makes it possible to reconstruct the course of the eruption with reasonable accuracy.[13]
Implications for volcanic hazards at Etna[edit]
The 1669 eruption represents a worst-case scenario of an effusive eruption at Etna;[21] over 500,000 people live in Catania[19] and a similar eruption today would cause about €7,000,000,000 damage.[125] Apart from the lava, tephra and lapilli associated with explosive activity would damage critical infrastructure close to the vent,[2] disrupt air travel, and impact both human health and the environment.[126]