REPORT ON THE RECENT GREAT ERUPTION OF THE

VOLCANO "STROMBOLI."

By FRANK A. PERRET,1

Volcanologist to the Volcanic Research Society of Springfield, Mass.

[With 9 plates.]

I have the honor to present, as you requested, the following report on the recent remarkable eruption of Stromboli, and particularly for the following reasons:

1. This eruption, together with the last one in 1907, differs so greatly from the characteristic activity of Stromboli as to mark a new era in the volcano's eruptive habit.

2. The eruption, although certainly the greatest in many years and imperiling the lives of the 5,000 inhabitants of the island, passed almost unnoticed by the press.

3. The writer, as well in 1907 as in the present year, was the only observer. The Italian volcanologists in both cases visited the island only after the close of the eruption.

Stromboli, at the northeast extremity of the Lipari group of islands, north of Sicily, appears as a small volcanic cone rising but 925 meters (3,033 feet) above the sea. It should be remembered, however, that what is seen is but the summit of a submarine mountain of great size and height. Its general form is shown in plate 1, figure 1, the principal characteristics being a divided and crested summit, an eccentric crater situated nearly 200 meters below the summit, a steep slope (35°) descending directly from the crater to the sea (the so-called "Sciarra del Fuoco"), and two plateaus on opposite sides of the island from the crater which form the inhabited and only habitable points.

The crater is thus invisible to the inhabitants and, while this undoubtedly contributes to their security and tranquillity, it is often, nevertheless, the cause of their ignorance of the volcano's condition especially as regards the preparatory symptoms of an eruption. The old semaphore station on Punta Labronzo was well placed for observation but was abandoned after the Calabrian earthquake of 1905, by which it was badly damaged. The new station above the town. of San Vincenzo is not in sight of the crater

1 Report to Mr. Handley, American consul at Naples, Italy, Oct. 26, 1912, transmitted to the Smithsonian Institution by the Department of State Dec. 30, 1912.

During the present generation the normal activity of this volcano has, until the events herein described, consisted of a moderate but almost continuous form of eruption with jets, at frequent intervals, of incandescent fragments of lava yielding an illumination so regular and brilliant as to have earned for Stromboli the title of "Lighthouse of the Mediterranean." There was no crater, properly so called, but a shallow depression where a crater should have been-that is, undoubtedly a filled-up former crater-with a number of small eruptive mouths generally arranged along the edge of the depression toward the sea. It will be seen that I do not claim that the present great crater, as described below, is a new thing in the life of the volcano, but that it is new to the present generation.

In the spring of 1907 the normal activity was broken by an eruption of great violence, which threw the inhabitants into a state of panic. The explosions were so sharp that the air concussion broke nearly every window on the island. The lava was thrown out in large masses so hot as to retain its plasticity and be conformed to the surface upon which the mass fell, as shown in plate 1, figure 2. The eruption lasted several weeks and produced a true crater 200 meters in diameter, and the eruptive mouths, with no exception, were sunk to the bottom of this abyss.

That they still existed and acted as separate mouths was proven by the varied character of the explosions and the different time intervals. There was also a most interesting rhythmic change from a type of explosion with the lava high in the conduit and in free contact with the atmosphere, when the cloud of ejected materials consisted of incandescent lava fragments (bombs) and clear vapors, to the opposite type of dense black volutes of ash from the collapsed wall material as the lava column sank below its former level. The difference between the two forms of explosion, known technically as "Strombolian and Vulcanian," was even more clearly defined in the eruption of 1912 and is clearly shown in plate 2. A considerable emission of ash having a strongly acid reaction ruined the grape crop for that year (1907) and the unfortunate inhabitants besought the Government, through the local municipal delegate, Signor Famularo, to send ships in case it seemed necessary to abandon the island. A cruiser, the Piemonte, and several destroyers were sent and it fell to me to assume the grave responsibility of assuring Commander Presbitero that the culmination of the eruption was passed and that, although some minor revivals of activity were to be expected, there was no further cause for alarm. Upon the strength of this he received permission from the Government to withdraw his ships. A brief account of this eruption was published in the Bulletin of the Brooklyn Institute of Arts and Sciences. This eruption of 1907 left, as I have stated, a deep crater 200 meters in diameter and was

followed by a long period of almost complete repose, this constituting quite a radical change from the foregoing habit of Stromboli and imitating the modus operandi of other volcanoes, such as Vesuvius and Etna. During this period not the least glimmer of light was to be seen at the crater and when I again visited the volcano in 1909 it was still in a state of quiescence. In this connection a fact of general interest may be mentioned. Some years previous to this time a project was on foot to erect a lighthouse upon "Strombolicchio." This is a monolith of lava (pl. 3, fig. 1) rising 50 meters above the sea at a short distance from the island. In my opinion it is a volcanic "neck;" that is, the solidified lava which existed in the conduit of a small volcano formerly active on this spot, the cone of which, formed of fragmentary materials, has been destroyed by centuries of weathering, leaving the solid core as a monument to its former existence. A flight of steps was cut from the sea level to the top and the top itself was leveled, but the project was abandoned, as I am informed, precisely because the illumination from Stromboli formed a better lighthouse than any which could be constructed by man. Upon the failure of the volcano a light was needed and a lighthouse is now to be erected upon Strombolicchio. The eruption of July-August, 1912, was, on the whole, greater than its predecessor and was initiated by a continuous series of violent local earthquake shocks. These undoubtedly were due to a conduit partly obstructed by lava which had consolidated therein. This was ejected in solidified form, as contradistinguished from that of 1907, in irregular blocks of all sizes up to two meters in diameter. One of these, shown in plate 3, figure 2, fell 500 meters distant from the crater. The rock is a compact, basaltic lava containing a considerable proportion of olivine.

Besides this rock the chief product of this eruption was the enormous quantity (for Stromboli) of ash. This reached a depth of over 2 meters on the upper parts of the mountain, as shown by the photograph (pl. 4) of a stone shelter built near the summit to shelter observers of the target practice of the fleet. In the towns the flat roofs were covered to a depth of 6 to 8 centimeters and, in contrast to that of 1907, this ash was alkaline but no less fatal to green vegetation. As long as the fallen ash remains dry it is harmless and a heavy rain is innocuous, as it washes the ash from the leaves, but if the ash on the leaf is moistened by the dew or a few drops of rain the soluble materials are extracted and attack the leaf, generally affecting one or more sectors, as shown in plate 5.

From the standpoint of the volcanologist, the most interesting feature of this ash is the fact that it is constituted almost entirely of new material-i. e., it was formed directly from liquid lava by inter