Volcán Etna, Sicilia, Italia

El Etna es un volcán activo en la costa este de Sicilia, entre las provincias de Messina y Catania. Tiene alrededor de 3.340 m de altura. Es el mayor volcán activo de Europa y la montaña más alta de Italia al sur de los Alpes. El Etna cubre un área de 1.190 km². Estromboliano, el volcán Etna no es sólo uno de los volcanes más activos en la Tierra, sino que es también uno de los más grandes, ya que mide más de 50 kilómetros de base.Tiene un cráter de cuyo camino parten conductos subterráneos, todos desembocando en pequeños cráteres adverticios que se abren en la zona superior de las laderas del monte. Las laderas de la montaña se dividen en tres zonas diferentes: la zona fértil cultivada, a unos 915 m de altitud llena de huertos subtropicales, plantaciones de cítricos y viñedos; la zona arbolada, de abundantes castaños , robles y pinos y la zona desértica, a partir de los 1, 920 m está cubierta de cenizas y fragmentos de lava y cuyos picos más elevados están cubiertos de nieve casi todo el año. La zona de cultivos está densamente poblada.

Morfológicamente el Etna es una gigantesca mole que ocupa una gran extension de la parte Este de la isla de Sicilia. Las laderas propiamente dichas empiezan a alturas variables entorno a los 1000 metros reconociendo una típica forma de cono truncado con pendiente moderada. A 2500 metros de altitud, donde la pendiente se suaviza, aparecen numerosos conos modernos, después, entre los 2900 y hasta los 3250 la pendiente se hace más abrupta, se trata del edificio somital, un enorme cono y varios cráteres con permanentes humaredas.

2001

El Etna, o lo que denominaremos la actividad volcánica en la zona del Etna comenzó como un volcanismo submarino hace unos 700.000 años, y ese “foco” fué desplazándose hacia el interior, lo que llevó a la aparición de un complejo edificio formado por la sucesión de diferentes erupciones en lo que se denomina un estratovolcán.
Existen crónicas de sus erupciones desde hace más de 2000 años, siendo la última de estas entre Julio y Agosto del 2001, que arrasó la estación de esquí construida en su flanco Sur. Actualmente hay movimiento sísmico que deriva ocasionalmente en alertas que no pasan de eso.

Las erupciones del Etna en el siglo XIX terminaron con la formación de un cráter de derrumbe, que actualmente posee un diámetro de 3 km y medio. En el año 1669, durante este ciclo, las coladas destruyeron parte de la ciudad de Catania, al Sur del volcán.
Otra erupción muy destructiva fue la de 1928; la lava alcanzó las proximidades de la costa Este, y destruyó el pueblo de Mascali.

El 14 de julio del 2006, una grieta abierta en el flanco E del cráter del Etna produjó un flujo de lava que llegó al Valle del Bove. La actividad estromboliana produjo ceniza en Catania (a 25 kilómetros al SE del volcán). El 31 de agosto, la actividad de la cumbre del cráter del SE produjo lapill y las expulsiones llenaron el cráter que se desbordó hacia el lado E el 5 de septiembre, formando una depresión circular. La lava y la actividad estromboliana de la cumbre continuaron hasta el 11 de septiembre. Al 19 de septiembre del 2006, el Centro de Investigaciones Vulcanológicas de Arizona, publica que la señal de alerta del volcán Etna se encuentra en color anaranjado.

HISTORIA SIGLO XX

11 August 2003 - present: intermittent explosive activity at the Northeast Crater, and later (starting early September 2003) also at the Voragine. As of mid-September 2003 no fresh magmatic material is reported to have been emitted by this activity

27 October 2002 - 28 January 2003: simultaneous activity on the NE flank (2500-1850 m) and S flank (2750-2600 m), resulting in the total destruction of the tourist complex and skiing area of Piano Provenzana and a portion of the "Ragabo" pine forest. Eruptive activity on the NE flank ends on 5 November, while strong explosive activity continues on the S flank, building a large pyroclastic cone. Lava emission on the S flank occurs briefly in late October and resumes on 13 November, producing flows to the SW and S. The Rifugio Sapienza area is severely threatened twice, in late November and mid December, by lava flows, which destroy three buildings. Between 25 November and 10 December, explosive activity shifts about 200 m upslope, building a second pyroclastic cone, before the activity returns to the first new cone. Heavy ash falls mostly affect the Catania area, repeatedly forcing the closure of Catania airport and leading to an 80% drop in tourism business. Pre-and syn-eruptive seismicity and ground deformation cause damage on the northeastern and eastern flanks. Lava volume: 10-11 x 106 m3 (NE flank) and about 25 x 106 m3 (S flank); tephra volume: about 50 x 106 m3. This is the only documented historical eruption of Etna that produced more tephra than lava, although its overall size is modest when compared to some of the huge eruptions of the 17th century and recent events such as 1950-1951 and 1991-1993

16 June - late September 2002: mild Strombolian activity at the Bocca Nuova and the NE Crater. The central pit of the NE Crater is filled to within 50 m of its rim. The activity ends abruptly after an earthquake along the Pernicana Fault (northeastern flank), which marks the onset of a major slide of the eastern flank and possibly opens the pathway for magma intrusion into the Northeast Rift, the site of a flank eruption five weeks later. The volume of erupted products is neglegible

17 July - 9 Aug 2001: a complex and destructive eruption from a total of seven eruptive fissures located between the SE Crater and 2100 m elevation on the S flank and at 2600 m elevation on the NE flank in the Valle del Leone; destruction of part of the Etna cable car, and the main lava flow threatens the town of Nicolosi. More extensive damage is prevented by the construction of earth barriers in the area of the Rifugio Sapienza. Strong phreatomagmatic activity at one of the eruptive fissures generates widespread ash falls, repeatedly forcing the closure of Catania airport. Lava volume: 25 x 106 m3.

29 July 1995 - 17 July 2001: nearly continuous, often very intense and spectacular eruptions at the summit craters, with periods of mild Strombolian and intracrater effusive activity, and about 120 discrete episodes of powerful explosive activity (most with tall lava fountains and tephra columns) and emission of fast-moving lava flows. These summit eruptions are the most intense and voluminous of the past 300 years, producing at least 100 x 106 m3 of lava and pyroclastics

1993 - mid 1995: occasional phreatic ash emissions from the Bocca Nuova and the NE Crater

14 Dec 1991 - 30 March 1993: major and destructive eruption from fissures on the high SW wall of Valle del Bove (at 3000 and 2400-2100 m elevation); lava flows repeatedly threaten the town of Zafferana Etnea; a variety of efforts are made to divert the menacing lava flows; blasting of the master lava tube in mid-May leads to successful diversion. Lava volume: 235 x 106 m3 (the largest volume produced by a flank eruption since 1669)

July-Aug 1991: Strombolian activity from the SE Crater

mid Nov - 30 Dec 1990: Strombolian activitya within the Bocca Nuova

July - 7 Aug 1990: Strombolian activity within the Bocca Nuova

16 Dec 1989 - 15 Feb 1990: violent lava fountaining and effusion from the SE Crater; explosive activity on 5 Jan 1990 is the strongest since many decades with up to 20 cm of tephra falling on the WNW flank and ash falling as far as the Aeolian Islands. The strongest of these paroxysms, on 5 January 1990, is estimated to have produced 15 x 106 m3 of pyroclastics alone

11 Sep - 9 Oct 1989: vigorous lava fountaining and effusion from the SE Crater followed by a flank eruption within Valle del Leone (2640-2550 m); a non-eruptive fracture system propagates to 1750 m elevation on the SE flank causing serious concerns.

4 Oct 1988 - 30 June 1989: Strombolian and effusive activity from the SE Crater

early March - 16 May 1987: phreatic explosions and minor Strombolian activity from the NE and SE Craters; phreatic explosion from the SE Crater on 17 April 1987 kills 2 tourists and injures 7 others

30 Oct 1986 - 27 Feb 1987: major eruption from fissures in Valle del Bove (2900-2200 m elevation), initially accompanied by lava fountaining at the SE Crater.

mid July - 24 Sep 1986: Strombolian and effusive activity from the NE Crater; initially reminiscent of the persistent mild activity in the 1950's and 1960's; very violent explosive activity with spectacular lava fountains on 24 Sep 1986 with ash fall reaching <100 km SSE from Etna; airport at Catania closed due to ash fall; formation of a large pit in NE Crater and loss of about 10 m in height

8 March - 13 July 1985: major eruption on S flank (2620-2150 m); initially accompanied by lava fountains and a lava flow from the SE Crater; eruptive fracture cuts through "Piccolo Rifugio" but lava flows do not reach as far as in 1983.

28 March - 6 Aug 1983: major and destructive eruption on S flank (2450-2250 m); lava flows destroy numerous buildings and tourist facilities in the Rifugio Sapienza area and above; efforts are made to divert the lava flow, but their success is subject to debate.
27 April - 18 Oct 1984: long-lasting explosive-effusive eruption from the SE Crater, similar to the activity at the NE Crater in the 1950's and 1960's; a cone 80 m high grows within the crater.

26 Nov 1981: NE Crater active

17-23 March 1981: major and dangerous eruption on NNW flank (2250-1120 m elev.); high effusion rates peaking at more than 100 m3 s-1 ; fast lava flows cut roads and railways and threaten the town of Randazzo and several villages; first eruption in that sector since many centuries.

late Jan - early March 1981: lava fountaining and effusion from the NE Crater, whose cone reaches an elevation of 3350 m, the highest ever measured on Etna

8 July - 26 Sep 1980: three episodes of violent lava fountaining from the NE Crater, building the cone to 3345 m altitude

11 Jan - Sep 1980: Strombolian activity from the SE Crater

16 July - 9 Aug 1979: mild Strombolian activity at the SE Crater and lava lake activity in the Voragine is followed on 3 August by vigorous lava fountaining and ash emission from SE Crater (causing closure of Catania airport), then lava emission from numerous fissures across the Valle del Bove to the E and ENE, and on the ENE flank outside the Valle del Bove; a lava flow seriously threatens the village of Fornazzo.

5 July 1979 - 3 Dec 1992: intermittent explosive-effusive activity within the Bocca Nuova and the Voragine; a phreatic explosion from the Bocca Nuova on 12 Sep 1979 kills 9 tourists and injures more than 20, after which excursions to the summit craters are no longer allowed

18-29 Nov 1978: still another eruption from the SE Crater and fractures to ESE, E and ENE within the Valle del Bove (2600-1675 m). Lava volume: 5 x 106 m3

24-30 Aug 1978: eruption from the SE Crater and fractures to ENE within the Valle del Leone (3000-2300 m).

29 April - 5 May 1978: flank eruption starting at the SE Crater, and fissures extend E into the Valle del Bove (3000-2575 m elevation).

29 Sep 1974 - 29 March 1978: numerous eruptive episodes at the NE Crater, formation of long-lived subterminal vents at 2625 m elev. in 1975-1976 and growth of a vast lava field; 20 short episodes of vigorous lava fountaining and effusion after July 1977, leading to rapid growth of the cone around the crater, which reaches 3340 m elevation

30 Jan - 29 March 1974: eruption on the W flank (at 1670 and 1650 m elevation); formation of Monti de Fiore I and II and effusion of short stubby lava flows; first eruption on W flank since 1843

19 Sep 1971 - May 1980: episodic activity from the Voragine and further collapse alternating with filling of the Bocca Nuova; at the end of this period, the Voragine is completely filled with lava

5 April - 12 June 1971: a multifaceted eruption occurs from a SW-NE striking fracture system from the SE flank of Central Cone across the Valle del Bove and beyond its N rim (from 3000-1800 m elevation); destruction of the old Etna Observatory (near Torre del Filosofo) and lava flows threat several villages on lower E flank; destruction of isolated houses; formation of an explosive vent that will later become the SE Crater, Etna's fourth summit crater

10 Jan 1966 - early April 1971: persistent activity with vigorous lava outflow from NE Crater; eruptive fractures related to NE Crater form in Valle del Bove in the spring of 1968; formation of a small collapse pit (Bocca Nuova) on the NW flank of 1955-64 cone in the Central Crater; further collapse of this pit leads to its gradual enlargement

17 Oct 1959 - 31 Dec 1964: violent eruptive (explosive-effusive) episodes from the Central and NE craters, growth of large cones around the Voragine and in the S part of Central Crater, forming a new summit

23 March - late April 1959: Central Crater active

Nov-Dec 1958: Central and NE Craters active

25 Aug 1957 - 3 May 1958: intense NE Crater activity

5 Feb - 7 May 1957: intense activity with lava flows from the NE Crater

5 April 1955 - 7 April 1956: vigorous activity from the NE Crater begins to build a sizeable pyroclastic cone and produces lava flows; a large pyroclastic cone grows at the Voragine in the Central Crater in Sep 1955 and in the center of the same crater in February-April 1956; very minor lava effusion from subterminal fractures within the upper Valle del Bove on 29 Feb - 2 March 1956

30 July 1953: doubtful eruption from unknown vent(s) in the summit area (possibly ash emissions caused by collapse within a conduit)

21 Sep 1951 - 30 May 1952: NE Crater active (probably only collapse within its conduit, no magmatic activity)

25 Nov 1950 - 2 Dec 1951: one of the largest eruptions of the 20th century, from a fissure on the ENE flank, within the Valle del Bove (2820-2250 m elevation); damage to cultivated land and isolated buildings.

2-4 Dec 1949: eruption splits across summit and extends into fissure systems on the S flank (3200 m) and NW flank (at 3150 and 2425-1900 m elevation).

24 Feb - 10 March 1947: eruption from the NE flank (with vents at 3050, 2350, 2300 and 2225 m elevation). Lava volume: 7 x 106 m3

29 Jan - 24 Feb 1947: NE Crater and Voragine produce lava fountains, a lava flow issues from the NE Crater

Feb-Oct 1946: NE Crater active

Late Oct 1945: birth of the Voragine by (non-eruptive) collapse in the NE part of the Central Crater, in the same location where large pyroclastic cones had grown between 1916 and 1922 and between 1939 and 1942

Early June - Oct 1945: NE Crater active

19 Sep 1942 - 15 Sep 1944: NE Crater active

5 July 1942: a very strong paroxysmal eruptive episode with tall lava fountains at the Central Crater, leaving a nearly uniform sheet of lava several tens of meters thick on the crater floor, which obliterates all former features (including the 1939-1942 pyroclastic cones)

30 June - 5 July 1942: eruption from the SW flank (2780-2250 m).

16 March 1940 - late June 1942: Intermittent, intense activity (punctuated by paroxysmal eruptive episodes during the first half of 1940) at the Central Crater with growth of cinder cones and intracrater lava effusion; at the end of this eruptive period the Central Crater is nearly completely filled with lava

7 July 1935 - Dec 1939: NE Crater activity followed by a resumption of persistent magmatic activity within the Central Crater in the summer of 1939. A large pyroclastic cone grows in the NE part of the Central Crater, in the same location where the "cono avventizio" had grown between 1916 and 1922. Lava rapidly fills the deep central collapse pit

5-7 Jan 1934: NE Crater

late July 1931 - Sep 1933: NE and Central Craters active

1 Nov 1930: NE Crater

2 Aug 1929: phreatic explosion at the NE Crater kills two climbers

2-20 Nov 1928: very destructive eruption on the ENE flank (inside the Valle del Leone and beyond its N rim at 2600, 2300-1400 and 1200 m elevation); the town of Mascali is entirely destroyed by the main lava flow, and important roads and two railway lines are interrupted. This is the only time since 1669 that an entire population center is destroyed by an eruption of Etna.

31 July - 20 Aug 1928: Central Crater (collapse?)

2 Jan - June 1926: NE Crater

27 Dec 1924 - Feb 1925 NE Crater

9 Oct 1923 - 1924: Central Crater active (collapse?)

17 June - 18 July 1923: major eruption on the NE flank (2500-1800 m), threatening the town of Linguaglossa. The Circumetnea railway and an important road are interrupted by the lava flow. Lava volume: 48 x 106 m3; tephra volume: 0.5 x 106 m3

15 March 1919 - early June 1923: Central and NE Craters active; growth of the "cono avventizio" reaches its maximum and is followed by incipient collapse in the center of the Central Crater. In May 1923 the NE Crater produces extensive lava flows, and a cone begins to build around the vent

29-30 Nov 1918: small eruption on the N side of the Central Cone and on the NW flank (3100-1900 m); this event was not observed by scientists, but its products were later found. Lava volume: 11 x 106 m3 (this is probably an overestimate, since the NW flank lava flow is much smaller than the 1949 flow in the same area)

March-Nov 1918: Central and NE Craters active; vigorous growth of the "cono avventizio" in the NE part of the Central Crater, and the NE Crater produces its first lava flow

24 June - early July 1917: strong lava fountaining from the NE Crater, explosions from the Central Crater

13 Nov 1913 - March 1917: activity from Central and NE Craters. A large pyroclastic cone, named "cono avventizio", begins to grow in the NE part of the Central Crater, in the same location where the Voragine will form some 30 years later

10-22 Sep 1911: major eruption on the NE flank (2550-1650 m), threatening the town of Linguaglossa.
Aug 1912: Central Crater active

Aug 1911: eruptive activity from NE Crater and Central Crater

27 May 1911: a collapse pit forms without eruption on the NE flank of Central Cone; subsequently, the NE Crater later grows at this site

27 Dec 1910 - 17 Feb 1911: Central Crater active with production of "Pele's hair"

23 March - 18 April 1910: major eruption on the S flank (2350-1950 m elevation): lava flows pass about 1 km W of Nicolosi.

20 May 1908 - 28 Sep 1909: Central Crater active

29-30 April 1908: brief eruption from a fissure high on the W wall of the Valle del Bove.

15 Nov 1899 - Aug 1908: Central Crater activity alternating with collapse and subsidence of the crater floor

1669