What Can We Learn from Records of Past Eruptions to Better Prepare for the Future?

2.1 Tambora, 1815

The Tambora eruption of April 1815 was one of the largest eruptions of the past 500 years, but was understudied until relatively recently (Self et al. 1984; Self and Gertisser 2015). Eyewitness accounts of the eruption were gathered at the time by the regional Governor, Stamford Raffles, who dispatched a team to deliver emergency relief to affected communities, and collect information on what had happened (see Oppenheimer 2011; Pyle 2017). It was only many decades later that others attempted to assess the wider impacts of the eruption. Heinrich Zollinger, a Swiss botanist, climbed Tambora in 1847, and later documented the scale and severity of the eruption, including the casualties (Zollinger 1855). The extent of the global consequences of the eruption became clearer once the stories of the ‘Year without a Summer’ of 1816 had been gathered, and linked to the eruption of Tambora (e.g. Milham 1924; Stommel and Stommel 1983; Stothers 1984), while the narratives of links to global health crises and economic collapse are still emerging (e.g. Post 1977; D’Arcy Wood 2014; Oppenheimer 2015). The Tambora event is a case study of a globally-disruptive event; and one that would benefit from further analysis, particularly in the context of communication and crisis management.

2.2 Krakatoa, 1883

Krakatoa was the first volcanic eruption with a global impact where news of the event travelled faster than the spread of the ash cloud. The newly completed international network of submarine telegraph cables ensured that the opening phases of the Krakatau eruption in summer 1883 were reported in The Times newspaper in London within 36 h of the event (Simkin and Fiske 1983; Winchester 2003). The aftermath of the climatic phase of the Krakatoa eruption in August 1883 was an early example of the use of crowd-sourcing to gather information about the far-flung impacts of an eruption. George Symons, a British meteorologist, chaired the Royal Society’s Krakatoa Committee. The remit of the committee was to collect information on the scientific phenomena attending the eruption, and Symons placed calls in early 1884 for ‘the communication of authenticated facts respecting the fall of pumice and dust… unusual disturbances of barometric pressure and sea-level (etc.)’ (Symons 1888, p. iv). The final report contained only a very brief outline of the relief efforts that followed the eruption (Symons 1888, p. 2), alongside more extensive eyewitness reports from those both at sea, and on land. To mark the centenary of the eruption, Simkin and Fiske (1983) collected together these and many other accounts, and refined the timeline for the unfolding events. The existence of a telegraph network meant that some of the otherwise transient records of events were recorded for Krakatoa in ways that had never before happened for an eruption of this scale. However, while analysis of this material could provide valuable insights into the nature of emergency communication and response during a large-scale volcanic emergency, the full potential of these records has not yet been realised.

2.3 Parícutin, 1943

The eruption of Parícutin, Mexico, was on a smaller scale, but had dramatic consequences for farming communities of the high Mexican plains. In February 1943, an eruption began without warning in the corner of a corn field. Over the next nine years, the new volcanic cone of Parícutin grew, eventually covering 25 km² of land with lava. To mark the 50th anniversary of the eruption, Luhr and Simkin (1993) collected and edited a volume of papers and reports—some contemporary with the eruption; others offering a retrospective analysis of the wider impacts of the events on those affected. Accounts document the first-hand experiences of farmers who first had to cope with the fallout of ash and cinders; then a ‘rain of mud’, when the rains arrived, and finally resettlement in new locations that had no connection to their original homes, and required them to adapt their farming practices to lower elevations. The value of this volume in bringing together a diverse range of papers on the physical, environmental and social impacts of a one-off eruption was considerable; but, as with the examples of Tambora and Krakatoa, lacked any formal analysis of crisis communications.

2.4 Other Examples

While there are volcanological studies of many past eruptions, there are rather fewer that extend to an analysis of the human impacts and responses. Recent work on historical eruptions of Vesuvius in 1906 and 1944 that explore human impacts, crisis management and emergency response (e.g. Chester et al. 2007, 2015) reveal some important lessons for dealing with future volcanic crises, at Vesuvius and elsewhere.

Deeper in the past, volcanic events and their impacts may only have been recorded in official and other records if the event was of sufficient scale to have required a response (evacuation, aid and assistance, rebuilding or relocation); and if the local governance systems collected and recorded such information. There are extensive records of natural hazard events from the Spanish colonial period of Latin America (e.g. Petit-Breulh Sepúlveda 2004, 2006; Hutchison et al. 2016), but scant records from, for example, Ethiopia (e.g. Gouin 1979; Wiart and Oppenheimer 2000): differences that in part reflect the spatial locations and numbers of chroniclers, and the security of the archives. Beyond this, large-scale natural disasters may be captured in oral histories that require patience, luck and persistence to piece together (e.g. Blong 1982; Johnson 2013).

4.1 The Kameni Islands, Santorini, Greece

First we consider post-caldera dome-forming eruptions on the Greek island of Santorini; a restless caldera in the Mediterranean. The volcano is well known to the local residents (e.g. Dominey-Howes and Minos-Minopoulos 2004), and intimately linked to the deep archaeological history of both Santorini, and the Aegean Bronze Age ‘Minoan’ culture (e.g. Marinatos 1939). It has a significant transient summer population of tourists; some of whom will have come to see the volcano and its hot springs.

Over the past 3000 years, a series of dacite lava and tephra eruptions have progressively built the Kameni islands; a 4 km³ edifice which now emerges above sea level within the caldera (Druitt et al. 1999; Nomikou et al. 2014; Table 1; Fig. 1). The first eruptions to form the nascent Kameni islands would have been exclusively submarine, but there have been at least 8 subaerial eruptions since 46 AD which have progressively enlarged the Kameni islands (Fytikas et al. 1990; Pyle and Elliott 2006; Nomikou et al. 2014). Of these eruptions, there are written contemporary accounts of six, and detailed accounts of all known eruptions since 1707.

Table 1

Historical activity of the Kameni islands, Santorini, Greece

Eruption date	Location	Primary sources
10 Jan–2 Feb 1950	Nea Kameni	Georgalas (1953)
20 Aug 1939–July 1941	Nea Kameni	Georgalas and Papastamatiou (1951)
23 Jan–17 Mar 1928	Nea Kameni	Reck (1936)
11 Aug 1925–Jan 1926	Nea Kameni	Reck (1936)
26 Jan 1866–15 Oct 1870	Nea Kameni	Fouqué (1879)
23 May 1707–14 Sep 1711	Nea Kameni	Gorée (1710)
1570 or 1573	Mikra Kameni	No primary records
1457	Palea Kameni	No primary records
726	Palea Kameni	No primary records
46–47	Palea Kameni (Thia)	No primary records
199–197 BC	Hiera (or Lera)	No primary records

Notes Full sources listed in Fouqué (1879); Stothers and Rampino (1983); Pyle and Elliott (2006); Nomikou et al. (2014)

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An eruption from 1707–11 was the first such event on Santorini to be documented in a journal (Box 1, Gorée 1710); and is the earliest eruption of Santorini for which early maps or sketches exist (Fig. 2). 150 years later, from 1866 to 1870, a major dome-forming eruption became the focus of a significant amount of contemporary observation and writing. This eruption led to the first treatise on the medical effects of volcanic eruptions and their gas emissions (da Corogna 1867), and was documented in considerable detail by Ferdinand Fouqué, leading to the modern ideas on the origin and evolution of calderas (Fouqué 1879). Contemporary observations of eruptions in 1866–70 and 1925–1928 detail the eruption progress, including rates of dome growth, of explosions, and lava extrusion. These datasets provide the essential quantitative information that underpin later forecasts for the style of future activity (e.g. Watt et al. 2007; Jenkins et al. 2015). The last of the eruptions of Santorini was in 1950, three decades before the installation of the first instrumental monitoring networks on the islands.

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4.2 Eruption Progress

This led to the hypothesis that the next eruption of the Kameni islands would be preceded by ‘general uplift of the edifice and discoloration of the sea, and anticipated some days to weeks in advance. The eruption would involve the early formation of lava domes, which would later act as a focus for vigorous, intermittent explosive activity’ (Pyle and Elliott 2006, p. 266).

The recognition of a relationship between eruption length and the interval between eruptions for the last 4 large eruptions of the Kameni islands, consistent with a model of a constant time-averaged deep supply of magma, also meant that it was possible to forecast the duration of a future eruption. While this analysis is entirely empirical—based on collation of observations from eruptions over the past 300 years—this approach is typical of the way in which much modern volcanology still operates; this analysis would not have been possible without the depth and breadth of contemporary descriptive materials accompanying the historical eruptions.

4.3 Precursors

Although the eruption record of the Kameni islands is well known, the record of anything that may have happened in between eruptions is almost non-existent. We know of precursors, or pre-eruption changes, for several eruptions (see Box 1), but apart from a mention of an earthquake swarm a few years prior to the 1707 eruption, there are no known reports or records of any sort of unrest that wasn’t subsequently followed by an eruption. This lack of evidence for ‘precursory behaviour that didn’t culminate in an eruption’ (non-eruptive unrest) is likely to be a common feature of many volcanic systems (Moran et al. 2011)—and likely to explain the poor correlation between ‘run up’ and eruption scale that is evident in the most recent analysis of these sorts of datasets (e.g. Passarelli and Brodsky 2012).

The lack of documented non-eruptive unrest and the volcanological model for ‘the next eruption’ was brought into sharp relief in 2011, with the start of the first modern volcano-seismic crisis on Santorini since the eruption of 1950. In January 2011, the first small earthquakes located within the caldera were detected by the local seismic network. This was clearly anomalous, since most of the detected seismicity in the region since systematic measurements began in the late 1980s has been associated with structures outside the caldera, most notably the submarine Kolombos volcano (Dimitriadis et al. 2005; Nomikou et al. 2012).

The event was readily identifiable as a period of volcano-seismic unrest, due to localisation of shallow earthquakes along a well-known fault system thought to have been responsible for the delivery of magma to the surface during previous eruptions; and from the patterns of uplift and ground deformation detected from the network of continuous GPS instruments and analysis of satellite radar interferograms (e.g. Newman et al. 2012; Parks et al. 2012). Later, field evidence also showed changes in the nature of the diffuse degassing around the summit craters. In early 2012, the authorities convened a Special Scientific Committee for the Monitoring of Santorini Volcano, and oversaw the deployment of a host of new instruments across and around Santorini, but fairly soon the unrest came to an end and nothing further happened (Aspinall and Woo 2014). No formal notice of the unrest was declared by the authorities until the event was effectively over (see Vougioukalakis et al. 2016), and although there are now a dozen or more scientific papers describing these events, there was no eruption and there is no record of the event in the Smithsonian Institution’s Global Volcano Programme dataset or associated reports.

Best estimates of the scale of the magmatic anomaly associated with the 2011–2012 unrest suggest that the shallow magmatic pressure source increased in volume by ca. 14–23 million cubic metres (Parks et al. 2015); equivalent to a couple of decade’s worth of ‘steady state magma accumulation’. This presents a challenge to the previous consensus model for the volcano: here was evidence for a large, shallow intrusion which did not lead to eruption. Whether this is the typical behaviour of the system, or not, is something that cannot yet be determined—because although the rich documentary record of past events furnishes us with the evidence for how the next eruption might proceed, it provides us with no information, one way or the other, about the frequency and style of episodes of unrest. However, the episode of unrest has stimulated new work on conceptual physical models for repeated eruptions driven by pressurisation and failure of the shallow magma reservoir by intrusion (e.g. Browning et al. 2015; Degruyter et al. 2016), and stimulated retrospective analysis of bathymetric maps, that chart the ups and downs of the volcano since the 1850s (Watts et al. 2015). The unrest has also opened up a public discussion of how the scientific community, civil defence and local authorities should plan for a future crisis; including how to manage hazards, risk and communications (Vougioukalakis et al. 2016).

4.4 The Soufrière, St. Vincent

4.5 Eruptive History and Impacts

St. Vincent lies in the eastern Caribbean, and is one of the southern islands of the Lesser Antilles Arc. The eruptive history of the presently active volcano—the Soufrière, a complex of craters at the top of the Morne Garou—is not well known prior to about 1700. Since then, St. Vincent has experienced four major explosive eruptions, and at least one minor dome-forming eruption (Fig. 1; Table 2; Robertson 1995). Eruptions in 1718, 1812 and 1902–3 each had major consequences for the northern sectors of the island—with widespread tephra fallout, explosive ejection of ballistic blocks, column-collapse pyroclastic density-currents, and lahars deposited across or coursing down the flanks of the volcano. Each of these explosive eruptions led to significant ash fallout across other islands of the Caribbean; notably Barbados.

The eruptions of 1812 (at least 56 fatalities; Robertson 1995) and 1902–3 (1600 fatalities) were severe, with much damage to properties, many associated with the sugar plantations in the northern parts of the island; and deaths in the communities which provided labour for those plantations (Anderson and Flett 1903; Smith 2011; Pyle et al. 2017). The details of the social and economic consequences of these eruptions can be reconstructed in an extraordinarily fine-grained way, principally because of the preservation of official correspondence and reports from the time in colonial archives (Gullick 1985; Smith 2011; Richardson 1997; Pyle et al. 2017).

There are no known reports, however, of the consequences of the explosive eruption of 1718 for the inhabitants of St. Vincent. The only written record of the eruption was gathered from the descriptions of European mariners, and published anonymously in a pamphlet that declared ‘the entire desolation of the island of St. Vincent’, and that ‘the island was no more’ (Box 2; Defoe 1718). This account was not mentioned by Shepherd (1831) in his history of St. Vincent, even though by that time the 1718 eruption would have been well known to natural historians from the works of de Humboldt and Bonpland (1825).

The eruption of April–May 1812 and its consequences were recorded in detail in a range of primary contemporary sources (letters and diaries) and published reports and accounts (see Smith 2011, for a detailed analysis). The diaries and reports of a British barrister and plantation owner, Hugh Perry Keane (Box 3) are thought to also have provided the materials for The Times leader story on the eruption, published six weeks later in late June (Smith 2011). Keane’s sketches of the eruption were later used by JMW Turner to inform his 1815 painting of the volcano in eruption. One notable feature of this eruption is the contrast between the published accounts that stress the ‘dreadful’ scale of the eruption, and the apparent light loss of life (Smith 2011). Estate owner Alexander Cruikshank wrote that ‘there has [not] been so violent an Eruption recorded since the destruction of Herculaneum and Pompeii’ (Blue Book 1813, p. 4), and a committee of landowners petitioned the Crown for compensation, on the basis that these ‘distressed Memorialists [had suffered a] severe visitation of Divine Providence… unexampled in any of His Majesty’s dominions for much more than a century’ (Blue Book 1813, p. 9). These accounts were presumably motivated by a desire for financial recompense, and stress the physical impacts of the eruption on their crops, estate lands and property. In contrast, the same reports are very thin on the consequences of the eruption either for their enslaved workers (one sugar estate owner appended the brief statement ‘but most providentially not many lives were lost’; Blue Book 1813, p. 4), or for the island’s native residents. Reports suggest that many people from the Carib communities who lived around the flanks of the volcano evacuated spontaneously within a couple of days of the eruption starting, but before the eruption reached a climax (Blue Book 1813; Smith 2011). It is not known whether this reflected a response based on oral histories of prior eruptions; or that the effects of the tremor and tephra fallout had become intolerable.

The catastrophic eruptions of 1902–3, in which about 1600 people were killed, left dense records of official and other communications during both the immediate crisis, and the relief and recovery efforts (Blue Book 1903, 1904; Anderson and Flett 1903). Eyewitness accounts of the build up to the eruption again suggest that significant numbers of people from communities living on the flanks of the volcano evacuated spontaneously during the 24 h before it reached a climax (Pyle et al. 2017). Indeed, by the time the scale of the eruption became apparent to colonial officials in Kingstown, telephone lines to the north of the island had already been interrupted and submarine telegraph lines from St. Vincent to the neighbouring island of St. Lucia had been severed (Report of Edward Cameron, Administrator; Blue Book 1903). A combination of the infrastructure of the Colonial Government; the relative ease of international communication (telegrams) and the coincidence of the devastating eruption of Mont Pelée, Martinique, just one day after the eruption of the Soufrière of St. Vincent meant that these two volcanic disasters in the Caribbean attracted world-wide interest at the time, and a rapid international relief effort (Pyle et al. 2017). Scientists and journalists arrived with some of the relief boats, and dramatic reports of the aftermath of the eruption were soon widely available (e.g. Russell 1902; Morris 1903; Anderson 1903; Hovey 1903a, b). Since that time, though, little of this material has been re-considered by volcanologists; and a full analysis of both the entire eruption sequence, and the recovery process has yet to be completed.

In between these eruptions, each of which were preceded by many months of felt seismicity in areas close to the volcano, there may well have been other small to moderate eruptions which were non-explosive, and which produced few noticeable consequences—whether in terms of detectable seismicity, or other manifestations. There has been speculation that an eruption in 1784 formed a lava dome which was subsequently described after the first known ascent by a European in late 1784. Anderson, who was then keeper of the newly established Botanic Station on St. Vincent, describes the nature of the crater in detail, along with a sketch map of the summit area (Fig. 3). This can readily be interpreted as a lava dome with actively degassing fumaroles—not greatly different from the current status of the dome, which extruded in 1979.

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During the ‘modern era’ there were two eruptions of St. Vincent, both of which were closely observed and documented. In 1971–1972 a ‘quiet’ effusive eruption led to the emplacement of a lava dome within the summit crater-lake. This was followed, just 8 years later, by a short but violent series of explosive eruptions (from April 13–26, 1979), followed by six months of the emplacement of a lava dome (Aspinall et al. 1973; Shepherd et al. 1979; Shepherd and Sigurdsson 1982; Huppert et al. 1982).

4.6 Challenges for the Future

In the context of anticipating future events, the detailed records of these past eruptions and their timelines (Fig. 4), would certainly inform the development of future eruption scenarios. But our understanding of the nature of any precursors is, as with the case of Santorini, rather limited, with just the two most recent eruptions having any instrumental monitoring record—the first of which made barely a trace in terms of detectable precursory seismicity (Aspinall et al. 1973).

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Each of the last four explosive eruptions were preceded by felt earthquakes in the north of the island; each of the eruptions for which the crater was flooded also showed short-timescale changes in the nature of the lake waters. There are no quantitative data on the nature of any pre-eruption gas emissions, since the most recent eruptions in 1979 occurred only just in time for the satellite monitoring era (Carn et al. 2016), and before the widespread adoption of volcanic gas measurement technologies. Nonetheless, there have been local crises on St. Vincent triggered by the appearance of sulfurous odors and haze. The most recent of these events occurred in mid-February 2005, and was detected both on the island of St. Vincent and on the Grenadines (50–75 km S). In the event, Seismic Research Unit scientists and the Soufrière Monitoring Unit determined that the cause of the event was purely meteorological in origin: the typical winds in the area take the fumarole emissions out to sea, and this event was ascribed to an unusual wind field (Weekly Report, Smithsonian Global Volcanism Project, March 2005).