Historical eruptions of Mount Etna

OVERVIEW

The record of Etna's eruptions goes back to about 1500 B.P., and its list of documented eruptions is the longest of any volcano in the world. This record is clearly dominated by flank eruptions which caused much more alarm among the people living near the volcano, so that the picture of Etna's historical eruptions is far from complete, especially during the period prior to the 17th century. You may see lists of eruptions before 1900, and from 1900 to present; these will contain more and more links to selected eruptions with brief descriptions, flow maps and images (and/or photos). The following is a brief analytical summary of the eruptive activity since 1600.

The past 400 years in the eruptive history of Etna are characterized by several changes in the eruptive behavior of Etna, which coincide with changes in the output rate (that is, the amount of lavas and pyroclastics produced in a given period). During the period from about 1600 until 1669, eight flank eruptions occurred in various sectors of the volcano, and some of them were of unusually long duration (1614-1624, 1634-1638, 1651-1653) and volume (1614-1624: about 1-2 km³; 1669: about 1 km³). The mean output rate during the period 1600-1669 was calculated by Hughes et al. (1990) at 1.19 m³ s^-1, considerably higher than during any period after 1669. The culminating and concluding event of that period was the devastating eruption of March-July 1669 which drained the central conduit system to the point that the summit cone collapsed, and the shallow plumbing system underwent a profound change. For nearly a century following the 1669 eruption, Etna's output was presumably very low (Hughes et al., 1990), and there were only three relatively minor flank eruptions in 1689, 1702 and 1755, all of which occurred within the Valle del Bove on the eastern flank of the volcano and whose volumes are unknown. Summit activity seems to have resumed after an unusually long repose period of 13 years, in 1682. Furthermore, there is no information about the amount of eruptive products produced during that period by the near continuous activity at the Central Crater which led to the construction of a new summit cone after the 1669 collapse.

The 1755 flank eruption was followed by several years of near-continuous summit activity including several overflows of lava. Then, in a period of three years, no less than four flank eruptions occurred in various sectors of Etna: February-March 1763 (W flank), June-September 1763 (S flank), 1764-1765 (N or NE flank), and 1766 (S flank). This peculiar "cluster" of flank eruptions heralded a period when the eruptive behavior of Etna was remarkably regular and the output rate was distinctly higher than during the period 1669-1755. From 1767 until 1865 there were nine clearly isolated flank eruptions, separated by intervals of about 10 years: 1780, 1792-1793, 1802, 1809. 1811-1812, 1819, 1832, 1843, 1852-1853, and 1865. The last eruption of that period, in 1865, emitted some 100 x 10⁶ m³ of lava and pyroclastics and thus was among the largest since 1669. A few weeks after the end of that eruption, a locally devastating earthquake (Magnitude 4.7) killed more than 70 people near the village of Macchia on the E flank of Etna (Boschi et al., 1995). This earthquake was related to displacements on a fault belonging to the "Timpe" fault system which lies at the intersection of the two major fault systems of eastern Sicily, the Malta Escarpment and the Messina-Giardini (or Messina-Etna) fault systems. Earthquakes originating from "Timpe" fault system have on various occasions followed eruptions on Etna (Gresta et al., 1987); Hirn et al. (1996) also recognized a possible correlation of periods with high output and large regional earthquakes. However, a clear causal relationship has so far not been confirmed due to insufficient data.

Since 1865 flank eruptions appear to occur in clusters, or series, and most remarkably, the last eruption in such a series is also the most voluminous (the 1928 eruption being an exception). Four such series occurred between 1865 and 1993: (1) 1874-1892, (2) 1908-1928, (3) 1942-1951, (4) 1971-1993. The latest of these series included no less than thirteen (13) flank eruptions, which, averaged over a time interval of 22 years, gives an interval of 1.5 years between the beginning of one flank eruption and the beginning of the next one. When flank eruptions resumed in 2001, it seemed likely that this was the beginning of a new series, and there was no reason to assume that the intervals between eruptions would be much longer than during the 1971-1993 series. In fact, the 2002-2003 eruption began less than 1.5 years after the beginning of the 2001 eruption. Future flank eruptions might thus occur at quite short intervals, and this is not a happy piece of news, especially in the light of the 2001 and 2002-2003 eruptions. Both were marked by simultaneous lateral and eccentric activity (see "Types and styles of eruptions"), and it is suggested that the eccentric activity was fed from a newly formed magma reservoir, which is largely independent from the central conduit system. It is not possible to foresee the future behavior of this new reservoir, but it is possible that it will grow and feed more eruptions, and at the same time the central conduit system will remain active and produce eruptions as well. What is certain is that Etna is becoming more complex before our eyes, and this makes it one of the most dynamic and fascinating volcanoes on Earth.

ERUPTIONS SINCE 1971

Copyright © Boris Behncke, "Italy's Volcanoes: The Cradle of Volcanology"