Let us take a closer look at the scenario of the main protagonist of the last 50 years: the Southeast Crater.
The birth of Southeast Crater in 1971
Let us start at the beginning: After a century of profound transformations and intense activity of the summit craters, on 5 April 1971, strong lateral activity gave way to a new phase characterised by 13 lateral eruptions over a period of 22 years, a unique period in Etna’s history.
First, two fissures formed on the southern slope at 3000 m, called the Vulcarolo opening and the Observatory opening. Due to the constant outpouring of lava, the lava flow covered an area of one square kilometre in 12 days, one tongue moved towards Monte Frumento Supino and others covered the Piano del Lago plain.
For about a month, the estuaries open and close between 2900 and 3100 metres, forming the Bocca Ovest (West Estuary) and the Bocca Est (East Estuary). Before the end of April, the lava flows destroyed the Volcanological Observatory and the cable car arrival station.
On 7 May, the lava stopped one kilometre from the Sapienza Refuge, marking the end of the activity of the mouths on the southern slope, but the beginning of that on the north-eastern slope, with the opening of a mouth at 2600 m altitude.
On 11 May 1971, eruptive activity shifts with undiminished intensity to the vicinity of Serra delle Concazze, heralding the beginning of what would later be called the Great Eruption of 1971. This gave rise to the beautiful Serracozzo Grotto, which we visit on our tours on the north side of Etna. Running between the towns of S. Alfio and Fornazzo, the lava flow reaches a height of 600 m above sea level.
During all this activity, with mouths opening and closing to the north, south and east, a lateral collapse created a pit crater (also called a shaft crater) on 14 May at an altitude of 3000 m at the south-eastern base of the central crater, from which ancient rock ash escaped and which served as a vent. At first glance, this is just an ordinary activity, but remember this date and this event! It is the first sign of what should be spectacular events in the next 50 years. For about a month, strombolian explosions and lava fountains occurred in this opening, then it was dormant for seven years.
It was only in 1978, with the formation of various fractures and strong explosive activity, that this pit crater began its career as Etna’s most active crater and was named the Southeast Crater.
From 1979 to 1980, 500 m high lava fountains and even volcanic lightning were formed at various times, which is quite an extraordinary event for Etna.
The Valle del Bove (ox valley)
From 1984 to 1986, there was another extremely productive phase of strombolian activity, in which one lava flow followed another, increasingly covering the Valle del Bove. This huge valley was a fantastic green oasis, a paradise of biodiversity, until the first fractures formed on the eastern flank of the central crater in 1971. Imagine a 37-square-kilometre valley that has been in the shadow of a great giant for millennia and, thanks to its proximity to the sea, has a wetter and cooler microclimate than the rest of Sicily, resulting in the formation of beautiful forests and lush areas ideal for raising sheep and growing fruit trees.
Every morning, the sun’s rays heat the black earth on Etna’s flanks, creating updrafts that carry hot air from the foot of the volcano towards the summit. On the east side, these updrafts suck in moist sea air, which cools down with increasing altitude. Since it is well known that cold air can no longer absorb the same amount of moisture, the moisture then condenses and forms clouds, which in turn bring shade and precipitation. This has created a special microclimate that has allowed the survival of several botanical species in the Valle del Bove and in large parts of Etna, which have evolved in a special way and have become endemic. Today there are over a hundred species with the name: aetnensis.
In addition to the young cone, two other mouths formed, one to the southwest and one to the west, the latter characterised by the rhythmic expulsion of gas and therefore called “bocca soffiante” (breathing mouth). In November 1988, another vent opened at the base of the cone, but it was not until September 1989 that another spectacle occurred as two lava fountains were ejected per day. On 26 October, a column of ash formed that towered over the entire volcano and took on the shape of a mushroom, similar to an atomic explosion.
The nineties, Rapid growth
On 5 January 1990, one of the most violent ash eruptions in living memory occurred, ejecting 23 million cubic metres of pyroclastic material. Fortunately, this eruption coincided with a storm that drove and dispersed the ash cloud northwards, over the sea and the Aeolian Islands.
On 14 December 1991, fractures opened north and south of the new crater, marking the beginning of the longest eruption of the century. At an altitude of 3100 to 2700 metres above sea level, 150 to 650 metre long fissures and 300 metre high lava fountains formed. The following day, the scenario shifted to below 2400 m. The very well-fed lava front moved rapidly into the Valle del Bove and the Val Calanna, and from then on the worrying phase for the inhabitants of Zafferana and surroundings began (it is still possible to visit the place where the most threatening flow came to a halt, after destroying “only” one house of Zafferana and coming to a halt a few metres before the second one). The nightmare for the population ended after 473 days, on 30 March 1993.
After a few quiet years, the development of the Southeast Crater resumed vigorously between 1996 and 2001, and in only five years it almost reached the height of the other summit craters.
In November 1996, a cone within the crater began a slow but sustained activity that resulted in small strombolian and effusive eruptions for 20 months. In July 1997, the produced material, which initially only poured inside the crater rim, began to overflow and flow into the Valle del Bove. By July 1998, the lava had covered the entire existing cone, whose total height was now 220 metres.
On 15 September 1998, a new, extraordinarily productive eruptive phase began, during which 18 events with very similar sequences took place: a few hours of strombolian activity, followed by lava fountains and finally ash columns. This resulted in a growth of about 100 metres. At the beginning of 1999, the time span between one activity and the next gradually decreased until they were only a few tens of minutes apart. On 4 February 1999, a long fissure formed, immediately showing the characteristics of a main eruption with ash columns 9 km high and remaining active for nine months, ejecting 50 million cubic metres of lava.
On 26 January 2000, another eruptive phase began, during which a fissure formed that crossed the crater from north to south. The paroxysms begin to intensify again, up to three per day, and the evolution of each phenomenon is also abrupt, going from strombolian explosions to lava fountains often 1000 metres high in a matter of minutes.
In March, a fracture on the southern flank creates a sort of dome called Sudestino, which remains the epicentre of the scene for a few weeks, before moving back to the summit of the Crater.
In April, the activities remained tremendous, but there were ten days between them. On 16 April, Sudestino produced lava fountains for the last time and Southeast Crater produced a strombolian explosion that lasts only 25 minutes but hurls lava chunks 6 km, also causing injuries.
The eruptions continued at intervals of 5 to 10 days until, on 24 June, a lava fountain reached a height of 1 200 m, was active for only 15 minutes and formed a lava flow 3 km long. Within six months, 66 paroxysms occurred, a globally unique event in which the southeast crater grew by 40 metres.
The 2001 and 2004 eruptions
On 20 January 2001, the vent on the north-northeast flank, later called “Levantino”, spoke up again. In the first six months of the year, the strombolian explosions followed each other, but with less intensity than in the previous year.
On 13 July 2001 everything changed, the lava fountains considerably enlarged Levantino, a series of earthquakes shook the eastern slope of Etna, and the first cracks opened at Piano del Lago, marking the beginning of the lateral eruption of 2001. We have already told you about this in another article (The eruption of Etna in 2001).
After the great eruptions of 2001 and 2002, there has been no noteworthy activity in the south-eastern crater, only a frequent formation of fumaroles, denoting the precariousness of the ground, which slowly led to a succession of collapses of the crater rim and a considerable increase in the diameter of the mouth, especially during the eruption of 2004-2005.
This eruption began on 7 September 2004 on the eastern flank of Southeast Crater. Various fractures form between 2850 and 2350 metres, the lava flows originate mainly at an altitude of 2650 metres, but the flows are only lightly fed and pour sluggishly into the Valle del Bove. The lowest point reached is at 1450 metres above sea level, still far from the inhabited centres, it poses no danger.
Collapses occur on 31 October and 16 February, forming a depression that sinks further in 2006 and 2007, forming a pit crater. The eruptive activity ends on 8 March 2005.
2006 and 2007
On 13 July 2006, a fissure opened on the southern flank, producing a cone and lava flows, again characterised by rather slow emission, which remained active for about ten days. In September and October, there was further activity very similar to that of previous years: effusive vents formed that were essentially free of explosive activity.
It was not until 20 October 2006 that Strombolian activity resumed from the South-East Crater, vehemently disrupting the lava field once again, splitting the cone that had just been formed and fracturing the flows that had just covered the side of the Crater.
After about a month, the activities are still powerful, but they alternate both from the summit and from the fractures at the base of the Southeast Crater, showing Strombolian activity and high columns of ash, until they end on 14 December.
In 2007, some rather short-lived Strombolian activity occurs, ranging from 1 to 10 hours, but these are the last of this crater until … well that’s another story, that you can find here: The New Southeast Crater