Flooding the Santorini Caldera

Flooding the Santorini Caldera

The flooded caldera of Santorini volcano holds many secrets, buried beneath the ash and pumice of its last great eruption. In the Late Bronze Age, about 3600 years ago, an explosive eruption several times larger that of Krakatoa, 1883, wreaked devastation across this thriving island.

View, looking North, of the northern part of the Santorini caldera. The island of Thersia (left) is separated from the island of Thera (right) by a channel, that is now thought to have formed at the end of the Late Bronze Age eruption.

View, looking North, of the northern part of the Santorini caldera. The island of Therasia (left) is separated from the island of Thera (right) by a channel, that is now thought to have formed at the end of the Late Bronze Age eruption.

A great trading port, Akrotiri, was buried under metres of pumice; preserving for future generations a snapshot of Late Cycladic urban life.

Akrotiri ruins

Bronze Age street scene – Akrotiri, Santorini. Precursory earthquakes damaged the town. But there was time for the residents to clear up rubble (foreground), and rescue furniture (those are casts of bed frames in the street), before the town was buried in pumice.

Once the eruption was over and the dust had, literally, settled the geography of Santorini would have looked much like it is today: a group of three islands, forming a ring around a caldera occupied by the sea. The central ‘Kameni’ islands would not have begun to emerge for another thousand years, or more.

But when did the sea flood the caldera, and what were the consequences? It has long been suspected that the Santorini eruption triggered tsunamis, implicated in Late Bronze Age destruction along exposed coastlines around the Aegean. Observations of the Krakatoa eruption in August 1883 include harrowing accounts of the great sea waves that swept across low-lying areas of Java, Sumatra as this eruption reached a climax. These tsunami were triggered either by the convulsions of the sea-floor, as the island of Rakata collapsed into the newly-forming caldera; or, as now seems more likely, by the displacements of colossal volumes of water as the pyroclastic currents raced into the sea.

Krakatoa - before and after images.

Krakatoa – before and after: notice how much of the island of Rakata (labelled Krakatau) has disappeared in the eruption; and the large shoals of pumice that formed new islands north-west of Krakatau (Proceedings of the Royal Geographical Society).

But could tsunami have been triggered by the Santorini eruption; and how? Until now it has been thought that collapse of the caldera could have triggered a tsunami; but only if the caldera was already flooded by the sea. A growing body of geological and archaeological evidence suggests that the crater of Santorini volcano was not open to the sea, as it is today, at least at the beginning of the Late Bronze Age eruption. Large blocks of stromatolites, an algal concretion, and chicken-wire gypsum that were caught up in the eruption debris point to the presence of a muddy lake in the northern part of Santorini. Before the eruption, this would probably have been an area of hot, bubbling mud-pools, fed by volcanic heat and fluids from depth. Among the wall-paintings from Akrotiri is one, the flotilla fresco, that shows a city on a hill, with a river running by. Are these features that might have been found inside the caldera of the volcano?

Metre-wide block of stromatolite, thrown out during the LBA eruption

Metre-wide block of stromatolite, thrown out during the LBA eruption, now in the entrance to the Heliotopos hotel.

In a new paper in Nature Communications, we present some new evidence that may help to resolve some of these questions. High-resolution mapping of the seafloor shows the presence of a remarkable scour at the northern end of the deep channel that separates the islands of Therasia and Thera, below the town of Oia. This feature can be seen on older sea-floor maps; but not in such detail. Using sound-waves to look at the structures that this channel cuts through shows that the channel didn’t form until most of the material thrown out in the eruption had already been deposited. The shape of the scour will be familiar to anyone who has built dams of sand on a wet beach, and then let it fail. This shape shows that the channel formed quickly, and that the sea broke through and poured down a great waterfall into the caldera, but only after the eruption was over. Any tsunami waves that formed during the eruption must have been triggered by the entry of the pyroclastic currents into the sea.

Image of the northern 'breach' in the Santorini caldera, and the scour and channel that cut through it.

Image of the northern ‘breach’ in the Santorini caldera, and the scour and channel that cut through it. From Nomikou et al., 2016.

This new evidence, along with new ‘cosmic ray exposure’ age measurements showing that the cliffs of the northern part of Santorini are ancient and formed before the Late Bronze Age, may strengthen arguments that the pre-eruption interior of Santorini island was not filled with seawater as it is today. It doesn’t, however, have any direct connection to the events that led to the collapse of the major Late Cycladic culture on Crete, the Minoan, a few decades later. Disruption caused by the loss of a major trading hub and short-term damage caused by fallout of ash across the islands of the eastern Aegean might well have contributed to the eventual decline and fall of Minoan culture; but the later destruction of the Cretan palaces must have another cause. Earthquake, anyone?

Selected references 

Heiken G, McCoy F, 1984, Caldera development during the Minoan eruption, Thira, Cyclades, Greece. Journal of Geophysical Research 89, 8441–8462

Manning SW et al., 2006, Chronology for the Aegean Late Bronze Age 1700-1400 B.C.,  Science 312, 565-569

Nomikou P et al., 2016, Post-eruptive flooding of Santorini caldera and implications for tsunami generation, Nature Communications 7: 13332, 8 November [open access]

Novikova T et al., 2011, Modelling of tsunami generated by the giant Late Bronze Age eruption of Thera, South Aegean Sea, Greece. Geophys J Int 186, 665-680.

Paris R, 2015, Source mechanisms of volcanic tsunamis, Phil Trans Roy Soc London A 373: 20140380

Pichler H, Schiering W, 1977, The Thera eruption and Late Minoan-IB destructions on Crete, Nature 267, 819 – 822


Thanks to NERC for funding for my work on Santorini; the organisers of NEMO 2016 and Heliotopos Conferences for a recent visit to Santorini; to Christos Doumas, Lefteris Zorzos, Clairy Palyvou and Maya Efstathiou for introductions to Akrotiri and the Late Bronze Age, and Floyd McCoy for discussions.

The smallest volcanic island in the world?

The smallest volcanic island in the world?
Oshima Ko Jima on May 4, 1805

Oshima Ko Jima on May 4, 1805. Sketch by Wilhelm Tilesius.

One of the delights of talking to children of primary school age is their disarming ability to ask really simple questions that demand straightforward answers, but leave you struggling to throw your academic caution to the wind. Even with the questions of the biggest, the smallest, the oldest and the youngest there are still different ways of (over)interpreting the question, that can leave you floundering. So for those of you looking for a clear answer to ‘what is the smallest volcanic island in the world?’, here is a suggestion of an answer from the early 19th Century. In 1805, Wilhelm Gottlieb Tilesius was engaged as the physician, naturalist and draftsman on the Russian ship Nadezhda, on the first Russian circumnavigation of the world. In May 1805, they were sailing across the sea of Japan and past the Matsumae peninsula in northern Hokkaido, heading for Kamchatka, when they came across two small volcanic islands ‘Oosima and Coosima’. Tilesius described Coosima (Oshima Ko Jima) as ‘perhaps the most diminutive volcanic island in the world’, noting that it was essentially a small pointed rock, which was incessantly smoking. The island was just ‘150 fathoms’, or 270 m, tall; lacking in vegetation and made of dark blue lavas with a weatherbeaten dark-red skirt around the base. Tilesius made all of his observations from on-board ship, as it took a quick tour around the island, and describes ‘light coloured smoke’ and ‘blue sulphur flame’ from the summit crater. Tilesius’ paper suggesting that this was the world’s smallest volcanic island soon found it’s way into Charles Daubeny‘s ‘Active and Extinct Volcanoes‘, and shortly afterwards in a number of popular periodicals of the time. Whether – with an area of 1.5 square kilometers – it really is the world’s smallest volcanic island; and whether it is actually ‘active’ are both moot points; in fact, so little seems to be known about the island that the Smithsonian catalogue still lacks a photograph of it.

Dr W Tilesius, 1820, On the Volcano called by the Japanese Coosima and situated in the neighbourhood of Cape Sangar, in the archipelago of Japan, Edinburgh Philosophical Journal, Vol III, no 6, October 1820, pp. 349-358.

Volcanoes of the Ethiopian Rift Valley

The great Rift Valley of Ethiopia is not only the cradle of humankind, but also the place on Earth where humans have lived with volcanoes, and exploited their resources, for the longest period of time. Perhaps as long ago as 3 Million years, early hominids began to fashion tools from the volcanic rocks from which the Rift Valley was floored, including basalt and obsidian.

IMG_7747_stitch Riftview

View into the Main Ethiopian Rift Valley, on the descent from Butajira to Ziway. Aluto volcano in the centre distance.

The Ethiopian Rift Valley is just one part of the East African Rift system – the largest active continental rift on Earth. While the Ethiopian rift hosts nearly 60 volcanoes that are thought to have erupted in the past 10,000 years, there is only very sparse information about the current status of any of its ‘active’ volcanoes. There are historical records for just two or three eruptions along the MER: 1631 (Dama Ali), and ca. 1820 (Fantale) and (Kone). In contrast, the Afar segment of the rift includes one volcano known to have been in eruption almost continuously since 1873 (Erta Ale), and several other volcanoes that have had major recent or historical eruptions (Dubbi 1400 and 1861; Dabbahu, 2005; the Manda Hararo Rift, 2007, 2009; Dallafilla, 2008, and Nabro, 2011). So are the volcanoes of the MER simply declining into old age and senescence? Or do they continue to pose a threat to the tens of millions of people who live and work the land across this vast region?

IMG_7836_stitch Shalla

Panorama of Lake Shala, part of which fills the huge caldera of O’a volcano.

To address this question, and others, the NERC funded RiftVolc consortium is carrying out a broad-scale investigation of the past eruptive histories, present status and potential for future activity of the volcanoes of the Central Main Ethiopian Rift. This spans eleven known or suspected centres, several of which have suffered major convulsions of caldera-collapse and eruption of great sheets of ignimbrite across the rift floor in the distant past. The first challenge is to piece together the eruptive histories of these volcanoes over the past few tens of thousands of years, and this is something that starts with fieldwork designed to detect the traces of these past events in the rock record. The RiftVolc field team, led by post-doctoral researcher Karen Fontijn, and with doctoral students Keri McNamara (Bristol) and Ben Clarke (Edinburgh) and masters students Amde and Firawalin (AAU) are spending the next five weeks completing a rapid survey of the volcanic ash and pumice deposits preserved within the rift.

IMG_8378_stitch CorbettiEast

Panorama of the eastern caldera of Corbetti volcano.

The first challenge is to identify the tell-tale clues that the sequences of young rocks, soils and sediments contain volcanic deposits. Close to the volcano, we might expect an individual large explosive eruption to leave both thick and coarse deposits; but go too close to the volcano, and there may be so much volcanic material that it can become hard to identify the products of single significant eruptions, as opposed to the ‘background noise’ of smaller but more frequent eruptions.


Karen and Keri examining the young pyroclastic rocks of Corbetti volcano

Out on the flanks of the volcano and beyond, we have the vagaries of geological preservation (did the pumice or ash land somewhere where it would then stay unmodified?) and erosion and weathering (removing or modifying the evidence) to contend with. Each of these factors will depend not only on the nature of the original deposit (how thick it was; what it was made from); but also on the environment in which the deposit formed (on a lake bed? the open savannah?  a forest? On a slope, or not?), and on the subsequent history of that environment (did the lake dry out, or continue to fill with sediment? Did the pumice become stabilised in the grass land; or did it get blown or washed away? How quickly did the soil and vegetation recover after the eruption? How deeply has weathering penetrated in the intervening millennia since the eruption?). Lots of questions to ponder!


Shelly fossils from an ancient lake deposit, interbedded with pumice layers from Aluto volcano

Our long-term goal is to better understand what sort of hazards the Rift’s volcanoes pose to those who live on and around them. There are, of course, much greater immediate challenges to communities in the region linked to the competition for the natural resources (water, land) in this region; but the rapid development of geothermal prospects in the Rift does mean that we need to pay closer attention to the state of the volcanoes that are the source of the geothermal heat.


Fresh road cut section through an obsidian lava dome and drape of pyroclastic rocks, on the way to Urji volcano and Corbetti’s new geothermal power plant

Aside from the volcanoes, the main Ethiopian Rift and its lakes make for a spectacular environment to work in. Despite receding lake levels and failing rains this year, there are vibrant patches of forest and a host of exotic birds and animals to enjoy.


Pair of little bee eaters, Lake Awassa


Flock of flamingo, Lake Chitu


Marabou stork, Lake Ziway





Camels eating Prickly Pear cactus, Corbetti


Ethiopian Fish Eagle, Lake Ziway

Acknowledgements. RiftVolc is a NERC-funded collaborative research project. Many thanks to our Ethiopian collaborators at the Addis Ababa University School of Earth Sciences and the Institute of Geophysics, Space Science and Astronomy (IGSSA) for hosting us and facilitating the joint field campaign; and to Ethioder for providing field vehicles and excellent drivers.

Maria Graham, and a large earthquake in Chile, 1822

Maria Graham, and a large earthquake in Chile, 1822

As news comes in of another very large earthquake in Chile – the third magnitude 8 earthquake along Chile’s Pacific margin in the past six years – this is a stark reminder of the destructive potential of these extreme natural events. These days we are used to the rapid, or near-real-time diffusion of news as these events unfold – in this case, as the tsunami ran along the Chilean coast, and propagated across the Pacific ocean. First indications are that the region that ruptured during the earthquake was a large section of the subduction zone plate boundary where the Nazca tectonic plate is sliding beneath the South American plate; close to an area that previously ruptured in great earthquakes in 1943, 1906, 1880 and 1822.

Map of historical rupture zones of large Chilean earthquakes. Source: United States Geological Survey.

Map of historical rupture zones of large Chilean earthquakes. The red dots show the locations of the 16 September 2015 earthquake and early aftershocks. Source: United States Geological Survey.

One of the earliest first-hand accounts in English of a large earthquake in this part of Chile comes from the writings of Maria Graham, who was living near Valparaiso in 1822; close to the source of the great earthquake of 19th November 1822, and within the region that was most hard hit by the event. Her journal – published in 1824 – records the event in great detail; and in particular, describes the dramatic coastal uplift that occurred as an immediate consequence of the event. A version of her report was later read to the Geological Society of London, where it caused a good deal of interest and, later, controversy.

View from Maria Graham's house. Bodleian libraries, Oxford, 4° R 56 Jur.

View from Maria Graham’s house. Bodleian libraries, Oxford, 4° R 56 Jur

Excerpts from Maria Graham’s ‘Journal of a residence in Chile, during the year 1822; and a voyage from Chile to Brazil, in 1823’,  London, 1824

November 20th, 1822.

At a quarter past ten [in the evening], the house received a violent shock, with a noise like the explosion of a mine. I sat still.. until, the vibration still increasing, the chimneys fell, and I saw the walls of the house open.. We jumped down to the ground, and were scarcely there when the motion of the earth changed from a quick vibration to a rolling like that of a ship at sea. The shock lasted three minutes. Never shall I forget the horrible sensation of that night. [Back in the house] I observed that the furniture in the different rooms .. Had all been moved in the same direction, and found that direction to be north-west and south-east.

Mr Cruikshank has ridden over from old Quintero: he tells us that there are large rents along the sea shore; and during the night the sea seems to have receded in an extraordinary manner, and especially in Quintero Bay. I see from the hill, rocks above the water that never were exposed before.

On the night of the nineteenth, during the first great shock, the sea in Valparaiso bay rose suddenly, and as suddenly retired in an extraordinary manner, and in about a quarter of an hour seemed to recover its equilibrium; but the whole shore is more exposed and the rocks are about four feet higher out of the water than before.

View of Quintero Bay

View of Quintero Bay, drawn by Maria Graham. Bodleian libraries, Oxford, 4° R 56 Jur.

December 9th, 1822.

in the evening I had a pleasant walk to the beach with Lord Cochrane; we went chiefly for the purpose of tracing the effects of the earthquake along the rocks. On the beach, though it is high water, many rocks with beds of muscles remain dry, and the fish are dead; which proves that the beach is raised about four feet at the Herradura. Above these recent shells, beds of older ones may be traced at various heights along the shore; and such are found near the summits of some of the loftiest hills in Chile.

In her journal accounts, Graham went on to speculate that repeated earthquakes could be responsible for the general elevation of land, and the building of mountains, in places like the Andes; themes that were later taken up by Charles Lyell, and then Charles Darwin – who was in Chile 13 years later, where he experienced the 1835 Concepcion earthquake firsthand.


IRIS Special Event Page, Illapel – great collection of resources on the Illapel earthquake

United States Geological Survey – Illapel earthquake information

The Maria Graham Project, Nottingham Trent University

Profile of Maria Graham on TrowelBlazers

Energy Poverty and Geothermal Energy Futures

Energy Poverty and Geothermal Energy Futures

Ethiopia is one of the most impoverished nations in the world, in terms of the number of people who live without access to electricity. The World Energy Outlook reported that in 2014, 70 million people in Ethiopia, or 77% of the population, have no access to electricity. Ethiopia is also one of the more volcanically-active regions of the world, with 65 volcanoes or volcanic fields that are thought to have erupted within the past 10,000 years – though few of these volcanoes have been studied in any detail; and fewer still are closely monitored.


Geothermal power plant infrastructure at Aluto volcano, Ziway, Ethiopia.

One benefit of this abundance of young volcanoes is that the geothermal energy potential of the region is significant – offering the potential of accessible and renewable low-carbon energy. Further south, along an extension of the Great Rift Valley, Kenya is already taking steps to exploit geothermal energy, with an installed capacity by December 2014 of 340 MW and an ambition to increase this by at least an order of magnitude within the next 15 years. In Ethiopia, current capacity currently stands at around 7 MW – provided by the Aluto Langano Power Plant, which was the first operational geothermal power plant in the country. In Ethiopia, as in Kenya, there is considerable ambition to develop geothermal power further – with the several volcanic centres identified as having the potential to supply 450 – 675 MW by 2020. In a country where per-capita electric power consumption is just 52 kWh (100 times less than that in the UK), that’s a lot of new energy.


Entrance to the Ethiopian Electric Power Corporation Aluto Langano Geothermal power plant, in the centre of Aluto volcano, Main Ethiopian Rift Valley.

All of this interest in young volcanoes as potential sources of ‘clean energy’ provides a significant opportunity for geoscientists to try and find out a little bit more about their eruptive past, and their potential for future activity; and to work out where the hot fluids and gases that provide the geothermal prospect are stored within the crust.

PP systems soil - CO2 measuring equipment

Using a PP systems respiration chamber to measure the escape of CO2 from the ground surface across the volcano.

At Aluto volcano, work by Will Hutchison using imagery from an aircraft survey (to identify young faults and fractures), and a ground-based survey of where (natural) carbon dioxide is seeping out of the volcano at the present day, has helped develop a cartoon ‘model’ for this volcano. Our current view is that Aluto volcano currently leaks quite small amounts of heat and gas to the surface; mainly along long-lived fractures and faults, some of which have origins older than the volcano itself. Inside the volcano, fluids are trapped under layers of impermeable rock – perhaps two to three kilometres below the surface – where they are heated by the warm rocks of the volcanic hearth.

Hutchison et al 2015 figure


Planned drilling campaigns on Aluto, and on the neighbouring volcano and geothermal prospect, Corbetti, should eventually fill in some of the gaps in our geological knowledge; and help to transform the energy futures of some of the millions of people who live along the Ethiopian Rift valley.


Hutchison, W., T. A. Mather, D. M. Pyle, J. Biggs, G. Yirgu, 2015, Structural controls on fluid pathways in an active rift system: A case study of the Aluto volcanic complex. Geosphere, 11, 542-562, DOI:10.1130/GES01119.1 [Open Access]

Kebede, S., 2012, Geothermal Exploration and Development in Ethiopia: Status and Future Plan, in: Short Course VII on Exploration for Geothermal Resources, 14 pp.

Data Sources 

World Bank – Electric Power Consumption

World Energy Outlook, Africa

Taking the pulse of a large volcano: Mocho-Choshuenco, Chile

Taking the pulse of a large volcano: Mocho-Choshuenco, Chile

As the recent eruptions of Calbuco and Villarrica in southern Chile have shown, the long arcs of volcanoes that stretch around the world’s subduction zones have the potential to cause widespread disruption to lives and livelihoods, with little or no warning. Fortunately, neither of these eruptions has, so far, led to any reported loss of life – but the consequences  of these eruptions for the communities living within reach of the ash plumes and beyond will continue to play out for months or years into the future.


The young cone of Mocho volcano, southern Chile, which may have erupted as recently as 1937. Mocho-Choshuenco volcano is one focus of our ongoing work in the region.

We have been working in southern Chile for a few years now, helping to extend what is known about past explosive eruptions at some of the region’s most active volcanoes. In this part of Chile, the written records of past eruptions only extend back a few hundred years – at the most – so most of our work has involved digging into the geological records of the region, to try and piece together the fragmentary stories of past eruptions. This can be slow and painstaking work, both in the field and in the laboratory, but is always exciting when things start to come together.

Field sampling on Mocho-Choshuenco volcano: deposits of the ‘Enco’ eruption.

This week, Harriet Rawson has published her first major scientific paper on the volcanic eruption history of Mocho-Choshuenco over the past 18,000 years. The 18,000 year timescale spans the volcanic activity that has taken place since the end of the last ice age; and we can be fairly confident that by visiting hundreds of sites around the volcano, we have found most of the ‘major’  eruptions, and many of the ‘moderate’ explosive eruptions from this volcano over this time period. The results of Harriet’s work are summarised in the picture below – which shows the timing, composition and sizes of eruptions through time. Just for context, the March 3 eruption of Villarrica was small (10 million cubic metres of ash, or magnitude 3 on the y axis), with a composition represented by an orange colour (so a bit like the Mocho eruptions around 4,000 years ago); while the April 22 eruption of Calbuco was moderate (210 million cubic metres of ash, or magnitude 4.5 on the y axis), and a composition in the green to pale blue range (like the eruption around 2000 years ago).


The record of explosive volcanic eruptions at Mocho-Choshuenco volcano over the past 18,000 years (from Rawson et al., 2015). The x axis shows time, as ‘thousands of years before present’, based on radiocarbon dating of flecks of charcoal preseved within the deposits. The y-axis shows the ‘size’ of the eruption, in terms of the eruption magnitude, which is a logarithmic scale of erupted mass or volume of ash and pumice. The coloured curves represent the age and erupted composition of the volcanic events that have been recognised – with the ‘peak’ of the curve showing the best estimate of the eruption age, and size. The width of the curve gives an indication of the uncertainty in the timing of the eruption. The cartoon parallel to the x-axis shows how regional climate and ice cover at the volcano are thought to have changed over the same time period.

In many ways, this work is just the start of the forensic process of understanding how this particular volcano works and of the threats it might pose for the future;  but it is also a critical piece of the jigsaw in terms of understanding the pulse of the volcanic arc, and crossing the gap between the geological past, and the volcanic present.


The wonderful ‘Salto Huilo Huilo‘ in the Huilo Huilo ecological reserve, at the foot of Mocho-Choshuenco.


This work has been funded primarily by the UK Natural Environment Research Council, and represents the outcome of many years of collaborations with colleagues from the Chilean Geological Survey, SERNAGEOMIN, with field work in the region supported by numerous colleagues and assistants, and with the support of CONAF and Reserva Huilo-Huilo.


K Fontijn et al., 2014, Late Quaternary tephrostratigraphy of southern Chile and Argentina, Quaternary Science Reviews 89, 70 – 84. [Open Access]

H Rawson et al., 2015, The frequency and magnitude of post-glacial explosive eruptions at Volcan Mocho-Choshuenco, southern Chile. Journal of Volcanology and Geothermal Research, doi:10.1016/j.jvolgeores.2015.04.003 [Open Access] Datasets available on figshare.

DM Pyle, 2015, Sizes of volcanic eruptions, Chapter 13 in Sigurdsson et al., eds, Encyclopedia of Volcanoes, 2nd edition, pp 257-264. doi:10.1016/B978-0-12-385938-9.00013-4

Calbuco erupts. April 22, 2015.

Calbuco erupts. April 22, 2015.

Volcan Calbuco, which burst into eruption on April 22nd, is one of more than 74 active volcanoes in Southern Chile that are known to have erupted during the past 10,000 years. Unlike its photogenic neighbour, Osorno, Calbuco is a rather complex and rugged volcano whose eruptive record has posed quite a challenge for Chilean geologists to piece together.

Volcan Calbuco (foreground), viewed on approach to Puerto Montt airport

Volcan Calbuco (foreground), viewed on approach to Puerto Montt airport


Calbuco’s volcanic neighbours, Osorno and Tronador.

The little that we do know about Calbuco’s eruption history comes from two sources: historical observations, and geological/field investigations. The historical record is not well known – other than that it has had repeated eruptions since the late-19th century. The eruption record prior to this is much less well known from written records, although the region has been populated for several millennia. The most spectacular recent eruption was in 1961, that ranked ‘3’ on the Volcanic Explosivity scale (VEI).

One interesting feature of Calbuco is that it is the only volcano in the area that regularly erupts magmas of an ‘intermediate’ composition (andesite), that contain a distinctive hydrous mineral, amphibole. This should make the eruptive products – particularly the far-flung volcanic ash component – quite distinctive. Preliminary work has identified the deposits of at least 13 major explosive eruptions from the past 11,000 years along the Reloncavi Fjord; but none of these have yet  been found further afield, even though they were the products of strong explosive eruptions (certainly up to VEI 5).

Calbuco is one of the many volcanoes in southern Chile that come under the watchful eye of the volcanologists from the Chilean Geological Survey, SERNAGEOMIN, and their Observatory of the Southern Andes (OVDAS); follow @SERNAGEOMIN for updates as the eruption progresses.

Further Reading

Find out more about our ongoing work on the volcanoes of Southern Chile

Fontijn K, Lachowycz SM, Rawson H, Pyle DM, Mather TA, Naranjo J-A, Moreno-Roa H (2014) Late Quaternary tephrostratigraphy of southern Chile and Argentina. Quaternary Science Reviews 89, 70-84. doi 10.1016/j.quascirev.2014.02.007 [Open Access]

Moreno, H., 1999. Mapa de Peligros del volcán Calbuco, Región de los Lagos. Servicio Nacional de Geología y Minería. Documentos de Trabajo No.12, escala 1:75.000.

Sellés, D. & Moreno, H., 2011. Geología del volcán Calbuco, Región de los Lagos. Servicio Nacional de Geología y Minería, Carta Geológica de Chile, Serie Geología Básica, No.XX, 30 p., 1 mapa escala 1:50.000, Santiago

Sellés, D et al., 2004, Geochemistry of Nevado de Longaví Volcano (36.2°S): a compositionally atypical arc volcano in the Southern Volcanic Zone of the Andes, Revista Geologica de Chile 31.

Watt SFL, Pyle DM, Naranjo J, Rosqvist G, Mella M, Mather TA, Moreno H (2011) Holocene tephrochronology of the Hualaihue region (Andean southern volcanic zone, ~42° S), southern Chile. Quaternary International 246: 324-343

Watt SFL, Pyle DM, Mather TA (2013) The volcanic response to deglaciation: Evidence from glaciated arcs and a reassessment of global eruption records. Earth-Science Reviews 122: 77-102

The great eruption of Tambora, April 1815


Map of the Sanggar peninsula, on the island of Sumbawa, Indonesia, and the crater of Tambora. From Heinrich Zollinger’s 1847 expedition to the crater, published in 1855. From University of Oxford, Bodleian Library Collection.

April 2015 marks the 200th anniversary of the great eruption of Tambora, on Sumbawa island, Indonesia. This eruption is the largest known explosive eruption for at least the past 500 years, and the most destructive in terms of lives lost, even though the precise scale of the eruption remains uncertain. The Tambora eruption is also one of the largest known natural perturbations to the climate system of the past few hundred years – having left a clear sulphuric acid ‘fingerprint’ in ice cores around the world, and evidence for a strong causal link to the ‘year without a summer‘ of 1816, and global stories of inclement or unusual weather patterns, crop failures and famine.

Much of what we do know about the eruption and its local consequences is down to the efforts of two sets of people: Stamford and Sophia Raffles; and Heinrich Zollinger. In 1815, Thomas Stamford Raffles was temporary governor of Java; the British having invaded in 1811. Shortly after the eruption of Tambora, he gathered reports from people in areas affected by the eruption, and put these together in an ‘account of the eruption of the Tomboro mountain‘, which was published first in 1816 by the Batavian Society for Arts and Sciences, and later published posthumously by his wife, Lady Sophia Raffles, in her biography of his life and works (Raffles, 1830).

There is a considerable scientific literature (see references below) which has documented the main phases of the eruption, which began in earnest on April 5, 1815, and built to an eruptive climax on 10 – 11 April 1815. It is thought that the volcano had been rumbling for some time prior to this, perhaps as early as 1812; and some of the contemporary records collected by Raffles suggest that the first ashy explosions may have begun by about April 1, 1815. An extract from a letter from Banyuwangi, Java, 400 km west of the Sanggar peninsula, describes this stage of the activity:

At ten PM of the first of April we heard a noise resembling a cannonade, which lasted at intervals till nine o’clock next day; it continued at times loud, at others resembling distant thunder; but on the night of the 10th, the explosions became truly tremendous. On the morning of the 3rd April, ashes began to fall like fine snow; and in the course of the day they were half-an-inch deep on the ground. From that time till the 11th the air was continuously impregnated with them to such a degree that it was unpleasant to stir out of doors. On the morning of the 11th, the opposite shore of Bali was completely obscured in a dense cloud, which gradually approached the Java shore and was dreary and terrific.


Heinrich Zollinger’s map of the inferred distribution of volcanic ash that fell across Indonesia following the eruption of Tambora in 1815. This may be the first example of an ‘isopach’ map of ash fallout from any volcanic eruption. From University of Oxford, Bodleian Library Collection.

The climactic phase of the eruption was very clearly described in an account by the Rajah of Sanggar, given to Lieutenant Owen Phillips, who had been sent to deliver rice for relief, and to collect information on the local effects of the eruption. ‘about seven PM on the 10th of April, three distinct columns of flame burst forth near the top of Tomboro mountain.. and after ascending separately to a very great height, their caps united in the air. In a short time the whole mountain next Sangar appeared like a body of liquid fire extending itself in every direction

In the main phase of the eruption, pyroclastic flows laid waste to much of the Sanggar peninsula, causing huge loss of life; and leaving a great collapse crater (caldera) where there had once been a tall volcanic peak.

Heinrich Zollinger was Swiss botanist, who moved to Java in 1841. In 1847, he led an expedition to Tambora and was the first scientist to climb to the crater rim since the eruption. In a short monograph, published in 1855, Zollinger describes his ascent of the volcano, documents the severe local impacts of the eruption, and details the numbers of people on Sumbawa affected by the eruption:

Location Killed in the eruption Died of hunger, or illness Emigrated
Papekat 2000
Tambora 6000
Sangar 1100 825 275
Dompo 1000 4000 3000
Sumbawa 18000 18000
Bima 15000 15000
Total 10100 37825 36725

Zollinger also estimated that at least 10,000 also died of starvation and illness on the neighbouring island of Lombok; and current estimates for the scale of the calamity are that around 60,000 people died in the region.

The bicentennial of the eruption of Tambora is a sobering moment to reflect on the challenges that a future eruption of this scale would pose, whether it were to occur in Indonesia, or elsewhere. Our present-day capacity to measure volcanic unrest should certainly be sufficient for a future event of this scale to be detected before the start of an eruption; but would we be able to identify the potential scale of the eruption, or its impact, in advance? Much remains to be done to prepare for and mitigate against the local, regional and global consequences of a repeat of an explosive eruption of this scale – and we still have more to learn by taking a forensic  look back at past events.


Auker, MR et al., 2013, A statistical analysis of the global historical volcanic fatality records. Journal of Applied Volcanology 2: 2

Oppenheimer, C., 2003, Climatic, environmental and human consequences of the largest known historical eruption: Tambora volcano, Indonesia, 1815. Progress in Physical Geography 27, 230-259.

Raffles, S, 1816, Narrative of the Effects of the Eruption from the Tomboro Mountain, in the Island of Sumbawa on the 11th and 12th of April 1815, Verhandelingen van het Bataviaasch Genootschap van Kunsten en Wetenschappen [via Google Books]

Raffles, S, 1830. Account of the eruption from the Tomboro Mountain, pp 241-250; in Memoir of the life and public service of Sir Thomas Stamford Raffles, F.R.S. &c: particularly in the government of Java, 1811-1816, and of Bencoolen and its dependencies, 1817-1824, with details of the commerce and resources of the eastern archipelago, and selections from his correspondence. London, John Murray.

Self, S, et al., 1984, Volcanological study of the great Tambora eruption of 1815. Geology 12, 659-663.

Sigurdsson, H. and Carey SN, 1989, Plinian and co-ignimbrite tephra fall from the 1815 eruption of Tambora volcano. Bulletin of Volcanology 51, 243-270.

Stommel, H and Stommel, E, 1983, Volcano weather: the story of 1816, the year without a summer. Seven Seas Press, Newport, Rhode Island.

Stothers, R.B., 1984, The great Tambora eruption in 1815 and its aftermath. Science 224, 1191-1198.

Zollinger, H., Besteigung des Vulkanes Tambora auf der Insel Sumbawa, und schilderung der Erupzion desselben im Jahr 1815. [Ascent of Mount Tambora volcano on the island of Sumbawa, and detailing the eruption of the same in the year 1815]

Links to online resources, and further reading

Bill McGuire ‘Are we ready for the next volcanic catastrophe?’The Guardian, 28 March 2015.

Gillen Darcy Wood ‘1816, The Year without a Summer’ BRANCH: Britain, Representation and Nineteenth-Century History. Ed. Dino Franco Felluga. Extension of Romanticism and Victorianism on the Net.

Haraldur Sigurdsson ‘Tambora: the greatest explosion in history’, a National Geographic photo gallery.

Tambora bicentennial – collection of papers in Nature Geoscience (Paywalled)

Gillen D’Arcy Wood’s Tambora; and an entertaining book review by Simon Winchester, author of ‘Krakatoa, the Day the World Exploded’

Anja Schmidt, Kirsten Fristad, Linda Elkins-Tanton (eds), Volcanism and Global Environmental Change, Cambridge University Press, 2015.

Friday Field Photo – Alutu volcano, Ethiopia

Aerial view of a young lava flow spilling into the central crater of Alutu volcano, Ethiopia. Note the trees and houses for scale.

Aerial view of a young silicic lava flow spilling into the central crater of Aluto (Alutu) volcano, Ethiopia. Note the trees for scale. This is an excerpt from air photo 2012321-00238 taken during flight campaign ET12-17 by the Natural Environment Research Council‘s Airborne Research and Survey Facility in Ethiopia, in November 2012, as a part of a wider investigation of the behaviour and history of this volcano.  If you want to see more images from this campaign, you can watch air photo montages of flights over Corbetti and Aluto volcanoes  on YouTube.

Update: June 2015

Our open access research paper on Aluto volcano is now available online: Hutchison et al., 2015, Structural controls on fluid pathways in an active rift system: A case study of the Aluto volcanic complex, Geosphere 11, 542-562, doi:10.1130/GES01119.1


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