History of the volcano: the vesuvio

THE ACTIVITY' OF THE VESUVIUS

Introduction

In the last 25.000 years, the volcanic activity of the plain bell is primarily assembled to the Vesuvius. The most ancient products are pumices (said pumices of Codola) that are found above the deposit of the Ignimbrite Bell. The most violent eruption is 17.000 years ago probably the happened one, called of the "Pumices of Sarno" or "Basal Pumices." Numerous other violent explosive eruptions are verified since then.

The Vesuvius enters the history of the volcanology with the eruption of the 79 d.C. After 1631, the volcano enters a state of persistent activity, with a to almost follow him nonstop of numerous explosive and effusive eruptions (you see tab. 2).

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The eruptions of the Vesuvius among the 79 d.C. and 1631

(line partly from A trip in the Vesuvius, P. Gasparini and S. Musella, 1991, And. Liguori, Naples)

After the 79 eruption on the Vesuvius a long silence and the first news of one persistent activity ("it sends forth a lot of ash that comes up to the sea") of his it falls you/he/she is brought in 172 by Galeno, a Greek physician that describes the ownerships of the dry air of the place created by underground fires.

Dione Cassio reports of a violent eruption in 203, whose boati is heard up to Capua, to 40 km from the Vesuvius. News of others two big eruptions happened in 472 and 512 are brought by Marcellino Comite chancellor of the emperor Giustiniano.

These it reports that November 6 th 472 "the Vesuvius, torrid mountain of Campania that it burns of inside fires, has vomited the bowel burnt; during the day handed her darkness with a dust draft on the surface of the whole Europe."

The 512 eruption is dettagliatamente described by Cassiodoro, a questor of king Teodorico, in a letter compiled for asking the exemption from the taxes for the populations damaged by the eruption. He reports that "it flies (...) an ash burnt that, after having formed some clouds pulvirolente, it also rains with drops of dust on the provinces of overseas (...). And' possible to see rivers of ash flow as flowing liquids that drag warm sands (...) and the back of the fields they inflate him to the sudden one up to reach the tops of the trees."

An explosive eruption, happened between 680 and 685, you/he/she is brought by Paul Diacono in the Historia Longobardorum and others are signalled in 787 and 968.

Leo Marsicano, in the chronicles of the abbey of Montecassino, speaking of the 968 eruption, it reports of "a huge and unusual fire that came up to the sea." In this eruption there is perhaps the first testimony of a casting of it washes, defined as "resin sulfurea that with nonstop impetus it fell toward the sea."

Numerous authors speak of eruptions to 991, 993 and 999, but being that years pervaded by the conviction of an imminent end of the world, every catastrophes reference must be reads with a certain border of suspect.

In the chronicles of the abbey of Montecassino another eruption is signalled lasted six days by January 27 th 1037 and an explosive event among 1068 and 1078. The last eruption, before a long period of quiescence, it happens to the beginnings of June 1139 and you/he/she is brought both from the chronicles of Montecassino and from those of the abbey of it Extracts some Tirrenis, as well as from the secretary of Pope Innocenzo II, Falcon Benevantano, which he/she wrote that the Vesuvius "it threw for well eight days powerful fire and alive flames."

Reliable testimonies don't be known on the activity of the Vesuvius after 1139. Around 1360, Boccaccio writes that from the Vesuvius "they don't now go out of it' flames of it' smoke."

In an undetermined year of 1500, Ambrogio Leone from Nola reports of an eruption lasted three days, which it followed the formation of gaseous fumarole. A Spanish soldier, climbed to the Vesuvius in 1501 together with the Regina Isabella, it described the crater as "a hole from 25 to 30 palms of diameter and from which continually goes out some smoke" that, according to some "it becomes the night an intense flame."

In 1575, Stephanus Pighius, a Belgian cleric in trip to Italy, the Vesuvius describes "dressed again from splendid vineyards, and so also the necks and the near fields." In the middle of his/her top it opens an abyss but the volcano "it is cold, of it' it seems to send forth some heat or smoke."

From 1500 1631 are therefore some that the Vesuvius has been inactive or almost. The mountain was covered of cultivations and the destroyed countries you/they had started over living quickly forgetting the past eruptions. Big trees grew up to the Gran Cone, the cone inside the caldera of the Sum, and the whole apparatus had called the mountain of Sum from the name of the city that rises to the feet of the Vesuvius.

In the night between 15 and December 16 th 1631, among strong boati and earthquakes, the Vesuvius returns in activity with a disastrous eruption that sows panic and destruction. Already from some months the whole zone was afflicted from frequent earthquakes, that intesificatis were him few days before the eruption.

Gianbattista Manso, a literate of the epoch describes the eruptive cloud that gets up partly toward the sky (column pliniana) and partly you/he/she dilates him on the strata of the mountain as a stream (surge and flows piroclastici).

The most violent phase lasted three days and the whole eruption he exhausted in five days, leaving a trailing of castings of mud and landslides of volcanic materials accumulated on the slant. Weak issues of ashes and earthquakes continued for months.

After this eruption the Vesuvius has changed form: the top, before taller than that of the Sum, it appears beheaded and the crater, according to Bouchard, a researcher French climbed up to the edge of the abyss, has a diameter of around two miles (three km and a half) in comparison to the preceding mile. Toward Tower of the Greek you/they had opened you are new eruptive mouths.

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The activity between 1631 and 1944

With the 1631 eruption the Vesuvius enters a phase of persistent activity that persists, brief periods excepted, up to 1944. For this it is probable that, gives the custom to see the volcano in activity, the testimony of the smaller events is lost and that the chronicles of the epoch bring only the particularly violent eruptions.

A lot of the eruptions that follow him for over three centuries introduce a very similar evolution: initial activity is type effusive, with castings of it washes that they gush out from fractures or tracimano from the edge of the cone. This phase can be accompanied by small explosions stromboliane.

After some days, the eruption becomes type explosive and fountains are formed of it washes tall 2-4 km. The final phase is characterized by the formation of a sustained eruptive column, tall 5-15 km, which follow the collapse of the central part of the crater. The volcano enters then a phase of rest that lasts some years. When it takes back, activity begins again with effusions of it washes.

The last eruption in the Vesuvius has still happened in 1944 and the following period of rest, that it persists to, it is very longer than you alternate him of rest that I/you/they are had in the period 1631-1944, lasted at the most 7 years.

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The 1944 eruption

May 10 th 1913 the fund of the crater formed him with the 19O6 eruption sinks of around 75 meters. Beginning from July 5 th 1913 the sinking is filled by an outflow of it washes, while cinders tossed up in the air accumulate forming a conetto.

Among 1915 and 1920 the fund of the crater gets up of around 100 meters. The first one I overflow of it washes out of the cone it happens later the 28 November of 1926 and three years, in June of 1929, a violent is recorded eruption. After this eruption, the Vesuvius alternates stasis and activity, for the more assembled inside the cone for quite a lot years.

August 12 th 1943 to the feet of the conetto opens an eruptive mouth, whose activity provokes the collapse of the conetto, followed by explosions. January 6 th 1944 the flow of it washes it increases and a casting pours again him to the outside pushing himself/herself/itself for over 100 meters to valley. It washes her continuous to actually flow to the outside of the crater to January 26 and inside the same up to February 23, day when effusive activity stops entirely.

In the first hours of March 13 th 1944 the walls of the conetto collapse and it stop every type of activity up to the afternoon of March 14, when they take back weak throwing of cinders. In the night between 17 and 18 March, with a mighty collapse of the conetto, it again stops every activity.

The evening of March 18 they are verified new explosions followed by an abundant issue of it washes that it marks the beginning of the 1944 eruption first phase ("effusive phase" Imbo', 1945). It washes her it overflows from the edge craterico in different points and it reaches, toward North, the side of the Sum from which is diverted to West toward the Ditch of the Vetrana.

The explosions increase and the throwing of cinders and shreds of it washes they actually reach 100 ms. of height above the edge of the crater. The evening of 19 washes her/it it reaches the first houses of Mass and S. Sebastiano, invades the inhabited areas and advances up to 1,5 km from the center of Cercola, where he stops on March 22.

From the morning of 19 the explosive activity he maintains constant with tumultuous throwing of cinders and shreds of it actually washes tall to 150 meters on the edge. From the evening of 18 to the morning of 19 they are warned Vesuviano to the observatory discontinuous tremblings and, from the hours 10 of 19, continuous tremblings with intermittent reinforcements.

To the 17 of March 21 the column of magma actually gets up to 2 Km of height and begins the second phase of the eruption that is defined, always from Imbo', "of the fountains of it washes."

The first fountain hard 30 minutes and it washes her/it incandescent, reverting and accumulating himself/herself/itself on the external slopes of the Gran Cone, it originates some pseudo-castings of cinders. One of these, particularly great, West-south-west is formed to where the 700 ms s.l.m reaches. To the I7,30s he/she returns an almost total calm with a notable reduction of the explosive phenomena and the cessation of the tremblings.

The eruptive break actually extends him at 20,10 o'clock, when it begins to be revealed a new lava fountain that lasts 20 minutes and introduces the same characteristics of the preceding one. Also this is followed by a general reduction of the eruptive activity. The alternate course of the continuous eruption to be repeated for the whole night and the morning of March 22. They follow 8 phases of fountains of it washes; with the last one the maximum eruptive is had of the whole paroxysm.

12 give some March 22 a gradual change it is verified and, besides the incandescent material, you/he/she is also sent forth material lithic torn by the duct. To this point it has beginning the third phase of the eruption, said of the "mixed explosions."

To the pseudo-castings of cinders, characteristics of the second phase, follow new phenomena of flow calls "incandescent avalanches" and "ardent clouds in miniature." The principal flow overlaps to the southern lava casting pushing himself/herself/itself, in few second, for 2 km over the edge craterico.

The central conetto, in reconstruction from March 18, he settles, in the afternoon of March 22, to the inside walls of the Gran Cone, reaching a maximum quota of over 1.260 ms s.l.m.

To the hours 21 of March 22, the explosions that last up to the first hours of March 23 for then to gradually decrease take back. During the same day the castings arrest him completely; that to South stops him to 350 ms s.l.m. (neighborhoods Mound-you Voccole) and that to North stops him to 120 ms s.l.m.

To 23 the 12, while the explosions are in decrement, they begin to always be warned an increasing number to the observatory of seismic shake. The seismic crisis precedes of few a new change in the eruption. In fact, from the 14, ashes and dark materials are primarily erupted and it start an alternation of seismic shake and explosions.

With the progress of this phase, said by Imbo' "sismo-explosive", it begins a gradual reduction of the phenomena. On March 24 continuous the issue of ashes that you/they become clearer. 27 and 28 the explosions are rare more and more and generally less violent and, 29, the eruption can tell him concluded. The whole activity reduces him to simple exhalations post-eruptive fumaroliche.

You finish the explosions, the walls of the crater and the sides of the Gran Cone they begin to be interested from phenomena of arrangement. On March 29 the crater introduces a central depth in comparison to the edge of 300 ms and a perimeter of 1,6 Km. The West edge, the more interested by the landslides, results to 1.169 ms and that Northeast to 1.300 ms s.l.m.

The edge of the crater also being irregular rather, it draws near, seen by the tall one, to the elliptic form with the greatest axle of 580 ms (East-west) and that smaller of 480 ms (North-south). For the continuous phenomena of landslide the crater suffers in the years following numerous modifications.

The eruption happens the arrival of the allied troops to Naples shortly after. Because of the war events, the observatory has become a meteorological station of the allies and its Manager, Joseph Imbo', you/he/she is relegated in an only stanzetta from which it completes its observations in the days of the eruption.

The event gathers of surprised the Americans and cause their great damages of an aerial bombardment: a whole flock of bombardiers B29 that was found in the field of landing in proximity of Terzigno is destroyed shortly by the ashes.

The Vesuvius seems so to want to manifest for the last time all of his/her power before reentering in a threatening rest that lasts to everything today. The only signs of its activity are some small earthquakes that are constantly recorded by the seismographs of the observatory Vesuviano and the activity fumarolica that is observed to the crater.