Historic Eruptions of the Kameni islands, Santorini

The Kameni islands have erupted seven times in the past five hundred years. Each of these eruptions has shown a similar pattern, starting with the growth of a lava dome and the slow extrusion of thick flows of lava, accompanied by intermittent but violent ash and steam explosions both from the vent, and as the lava flows enter the sea. Eruptions have typically lasted for extended periods – from a few months to a few years – and the main hazards associated with the eruptions have been similar in each case: the ejection of blocks and bombs during explosions; the formation of 2-3 kilometre high plumes of volcanic ash, and the release of large quantities of volcanic gases both from the vent and as hot lava enters the sea. The likely regions that could be affected by these different hazards have been delineated most recently by Georges Vougioukalakis and Michael Fytikas in 2005.

All of the historical eruptions have erupted lava of approximately the same composition, and it is likely that this sort of eruptive behaviour has been continuing on and off for the past few thousand years. For this reason, it is expected that future activity on the Kameni islands will follow a similar pattern to the historical eruptions.

Although there is an extensive literature that describes the historical eruptions, there is not nearly as much information available on the precursory signs that led up to eruptions; and there is almost no information at all on signs of unrest which were not subsequently related to an eruption. At the present day, we have the capacity to detect both small ground movements (associated with movements of fluids or molten rocks at depth), and small earthquakes which would not previously have been noticed – so there is no equivalent record of similar sequences of events that might have happened in the past.

Eruption date Location References and notes
10 Jan – 2 Feb 1950 Nea Kameni Small lava dome extruded.
20 Aug 1939 – early July 1941 Nea Kameni Extrusion of lava domes and flows; summit crater explosions, and ash plumes.
23 Jan – 17 Mar 1928 Nea Kameni Extrusion of lava domes and flows; summit crater explosions, and ash plumes
11 Aug 1925 – Jan 1926 Nea Kameni Extrusion of lava domes and flows; summit crater explosions, and ash plumes
26 Jan 1866 – 15 Oct 1870 Nea Kameni The largest historical eruption of the Kameni islands.
23 May 1707 – 14 Sep 1711 Nea Kameni The first well-described historical eruption of the Kameni islands.
1570 or 1573 Mikra Kameni Extrusion of a small lava dome.

source: http://www.santorini.com/santorinivolcano/volcaniceruptions.htm

Precursory activity on the Kameni islands

The limited precursory activity from historical eruptions described in the literature is summarised below. The main picture that we get from all of the published work is:

  • There may be an extended period (weeks to months) of weak earthquakes before an eruption, but eruptions are not necessarily accompanied by strong earthquakes.
  • Most eruptions are preceded (weeks to months) by observed changes in the sea around the volcano: perhaps changes in colour (due to turbidity and gas emissions), or temperature, or in the smell.
  • Most eruptions are preceded in the few days before eruption by significant evidence for land movements near the future location of the vent. Both uplift and subsidence (usually by tens of centimetres) have been noted.

In many cases the start of the eruption has been first noticed by the formation of plumes of steam and ash, though it is likely that most eruptions actually begin with the formation of a lava dome, and the emergence of this dome from the submarine flanks of the volcano.

1707 eruption. Goree (1710) notes that weak earthquakes were reported in the 5 days before the eruption, but that for 'a long time before these earthquakes fishermen noted ill smells every time they passed by' the region where the eruption began. When the eruption occurred, it began with 'subterraneous fires, several violent earthquakes, a roaring noise.. sulphurous exhalations and a black smoke..'. Goree also comments 'there have not been any other earthquakes at Santorini than those which, 14 or 15 years ago, continued for several days and were very violent'.

1866 eruption. 26 January 1866, (strong) signs of ground movement on Nea Kameni were noted by the only resident. Eruption proper probably began on 1 February. Fytikas et al., (1990) report that there were 'increases in seawater temperature, and some subsidence of the shores in volcano bay. The first lavas were slowly extruded, and the first explosions followed two days later.'

1925 eruption. Washington (1926) reports 'The first indications .. were slight earthquakes felt at Phira on July 28 and August 7, 8, and 9, and the rise in temperature of the water about Mikra Kameni. There is no record of the subsidence of the land, which was the most marked initial feature of the January 1866 eruption ... but as the islands were uninhabited, such may have occurred.

Ktenas (1926) says 'Before August, several weak earthquakes were felt at Fira (the 17th and 30th of March; the 10th and 18th July'. The first indication of volcanic activity (on August 11th) was the appearance of a column of white vapour.. the first explosion occurred later, producing a grey ash plume and ejecting stones, lapilli and ash.

Fytikas et al (1990) remark that the eruption was preceded by an increase in temperature in Kokkina Nera bay (NE Kameni), and the subsidence of Nea Kameni's east shore. The activity began with steam explosions in Kokkina Nera bay.

1939-1941 eruption. Reports on the web state that 'early in May 1939, it was observed that the waters in the little bay of Agios Georgios with its chapel, were heating up, and the coastline was subsiding', but I cannot find the published source for this. Fytikas et al (1990) note that no earthquakes were reported before the eruption, but ground fracturing was noticed ten days before the eruption began.

1950 eruption, Georgalas (1953) reported 'occasional small earthquakes which were felt at irregular intervals from 15 December 1949.' The eruption began on 10th January with a series of weak explosions, and small earthquakes. Later that morning, a stronger explosion threw out ash, and subsequent explosions produced both steam and ash plumes. There was also strong fumarolic activity around the 1940 domes.