What are volcanoes, and why do they exist?
Volcanoes are places on the Earth’s surface where molten material (magma) can erupt. This definition will work on other planets and moons — even the icy moons of the outer solar system, where the ‘magma’ may be a chilly mixture of water ice, methane and ammonia. On Earth, most volcanoes erupt magma that is rich in silica, and that solidifies to form rock, like pumice or lava.
Volcanoes are a part of the Earth’s internal cooling system. The inside of the Earth is hot, and gets hotter with depth. In some places, between about 50 and 150 km deep, the rocky interior is hot enough to melt, forming droplets of magma that will then percolate up to the surface. Often, this magma also contains dissolved gases — like water (steam), carbon dioxide and sulphur — that leak out of the magma near the surface; or bubble out violently, causing an eruption. Over geological timescales this escape of hot magma from within leads to the slow cooling of the planet.
But not all volcanoes are created equal, right?
As a volcanologist, it is easy to revel in the differences between volcanoes: they all look different, and come in a spectrum of shapes and sizes. While this diversity may reflect underlying differences in the particular geological setting (where the magma is from, how old or thick the crust is, and the history of growth, and weathering), in the end all volcanoes are formed by the same sorts of processes.
Some of the most remarkable volcanoes that I have been lucky enough to visit include the Greek island of Santorini, with its spectacular flooded crater, and its vast multi-coloured cliffs that reveal its hyperactive past; and the mysterious Tanzanian volcano, Ol Doinyo Lengai, with its chocolate-coloured lava flows of molten washing soda. Then of course, there are the remarkable volcanoes I haven’t yet managed to visit: Paricutin, the cone that grew in a Mexican farmer’s cornfield; or any of the deeply-submerged volcanoes that dot the ocean floor.
What is the significance of volcanoes to life?
On geological timescales, volcanoes can be thought of as valves that help the exchange of gas, rock and heat between Earth’s interior and surface. At the present day, humans are busy releasing so much carbon dioxide that the contribution from volcanoes is dwarfed – by about a factor of 60. But for billions of years before the industrial revolution, volcanoes helped to keep climate equable — as part of Earth’s life-support system.
There are compelling arguments that underwater volcanoes may have played a role in the origins of life: again, by providing sources of energy, and reactive chemicals, to the ocean floor.
“William Hamilton arrived in Naples in November 1764 as Britain’s envoy to the Spanish Court at Naples, and soon became besotted with Vesuvius.”
There is also strong evidence that links great outpourings of millions of cubic kilometres of ‘flood basalts’ with some of the most severe environmental changes on Earth – including some of the great ‘Mass Extinction’ events, such as the end-Permian in which 80-95% of all living species died out. Some of the most severe climate shocks of the past few thousand years can also be ascribed to volcanoes; such as the short, sharp cooling events after explosive eruptions of Rinjani in 1257 AD, and Tambora in 1815. Whether volcanoes pose an existential risk to the future of humanity, or civilisation remains an open question!
What are some of the most intense experiences you’ve had in your study of volcanoes?
My first encounter with volcanoes was at the age of seven, in Chile. We were living in Santiago, and drove down to the Chilean Lake District for a summer holiday. We camped at the foot of one volcano, and I have vivid recollections of sitting on the young deposits from the recent eruption of Villarrica. Thirty years later I returned, and this time hiked to the ice-clad summit crater, which was gently fuming and dusting the ground with a delicate golden honeycomb pumice.
I have had the extraordinary privilege to visit, and study, volcanoes in the most amazing places. In Tanzania, we climbed the bizarre volcano of Ol Doinyo Lengai shortly after it began a new eruption of sodium carbonate lava. We arrived at the summit in such dense cloud that we couldn’t see the crater’s edge, but the noise of the bubbling and bursting lava pools sounded just like a Victorian railway station.
One recent experience that stands out, though, was hearing eye-witness accounts and handed-down stories of a couple of eruptions on the Caribbean island of St Vincent. We were in the school, in the village of Sandy Bay; home to a community who were displaced repeatedly after eruptions in 1902, 1971 and 1979. Richie Robertson, director of the regional Seismic Research Centre opened the meeting with a reading from Shake Keane’s poem ‘Volcano Suite’, written during the eruption of 1979: ‘The thing split Good Friday in two’. This set the scene for some deeply moving and occasionally hilarious stories of ash, evacuation, emergency shelter, and recovery.
In Volcanoes: Encounters Through the Ages you explore how people across history have interacted with these fiery monsters. Could you tell us about some of the notions people had before the development of our modern scientific understanding?
Folk stories of volcanoes often tell the story of the landscape in terms of battling giants, or thwarted lovers. The volcanoes may be imagined as the petrified relics of these creatures, or as the home of the spirits. Some tales, like Ragnarok, may depict the fiery destruction of an eruption, as the land is engulfed in ash or lava, followed by recovery and rebirth.
Volcanoes must have seemed remote and mysterious to the inhabitants of the tectonically-quiet reaches of Northern Europe. The activity of Vesuvius and Etna would have been known from tales of classical Italy; and, later, Hekla, Iceland, with its vomiting stones and fire. From medieval times, volcanoes, fire and brimstone (sulphur) were often linked to the underworld, or seen as portals to hell.
During the seventeenth century, Vesuvius began a long period of activity, which continued up until 1944. It attracted the attention of natural philosophers like Athanasius Kircher (1602-1680) who began to wonder about what the source of the fires was — could it be bitumen? sulphur? — and where the heat came from. Kircher built on ideas developed by Plato, and imagined that the Earth contained a central furnace, linked by networks of fiery channels to a series of chambers and hearths that fed volcanoes at the surface. Others, like John Ray (1627-1705), noticed that some volcanoes appeared to erupt simultaneously, and speculated that they shared subterranean connections.
Your first book choice is Campi Phlegraei (1776) by William Hamilton, together with the Supplement (1779). What is the significance of these books?
William Hamilton arrived in Naples in November 1764 as Britain’s envoy to the Spanish Court at Naples, and soon became besotted with Vesuvius. He climbed it regularly, often escorting visitors, and kept notes of the changes he observed. After a dramatic eruption in late 1765, Hamilton wrote the first of several letters to the Royal Society documenting ‘the many extraordinary appearances’ he had witnessed. Vesuvius continued to wax and wane, and Hamilton engaged a painter, Pietro Fabris, to accompany him and sketch the volcano and its activity. In 1776, Hamilton published ‘Campi Phlegraei’, named after the nearby volcanic field. This sumptuous book includes Hamilton’s letters on Vesuvius, and more than fifty vibrantly hand painted illustrations, derived from Pietro Fabris’s sketches. After another dramatic eruption in August 1779, Hamilton commissioned more pictures, which he published as a supplement.
This monumental work was one of the first devoted to the detailed study of a volcano and its ongoing activity, and for this reason Hamilton is regarded as the first volcanologist of the modern era (Pliny, to whom he liked to compare himself, being the very first!). Thanks to Hamilton’s writings, we have a very detailed picture of the behaviour of Vesuvius from the mid-eighteenth Century, and of some significant eruptions whose deposits have now largely been buried or lost.
Your second choice is Fire Fountains (1883) by Constance Gordon Cumming. Why do you recommend this book?
One of the pleasures of researching my book on volcanoes was to discover new stories and writers. Constance Gordon Cumming was a writer and painter, who travelled independently across vast reaches of the Pacific Ocean in the 1870s. After visiting Fiji, New Zealand, Tonga and Tahiti, she eventually landed on Hawaii in October 1879. Fire Fountains is her account of her stay on the island, mostly in the form of letters home to her sister.
For me, the highlights of the book are her accounts of the long hike up Kilauea volcano to see the fire fountains and lava lake in the summit crater. On her first ascent, her thirty-mile hike through forest and across a frozen ‘billowy ocean of lava waves’ was rewarded with a sight as gloomy as the view from a Scottish mountainside in fog. The lava had gone, and there was no fire to be seen. Undaunted, she returned a few weeks later, and was rewarded with glorious views of cascades of molten lava.
How do historical accounts like Cumming’s help researchers like you understand volcanoes?
Records of fleeting glimpses of activity at remote volcanoes, such as those by Cumming, are important elements when trying to piece together the past histories of volcanoes. Although volcanologists are naturally drawn to work on erupting volcanoes, most volcanoes spend most of their time not erupting. Of the 850 volcanoes that have had a confirmed eruption in the past 10,000 years, and are expected to erupt again, the majority have been quiet for at least 100 years. Many of the most well known eruptions of the past 30 years happened at volcanoes that had not erupted for centuries, including Pinatubo (Philippines, 1991), and the Icelandic eruption of 2010 (Eyjafjalljökull).
Before the next eruption happens at a long-dormant volcano, we’d like to know two things: what is the geological evidence for what happened during past eruptions? And are there any accounts of past activity? Since the physical deposits of small eruptions may be hard to find or, more likely, lost through erosion and weathering, any accounts of how a volcano behaved in the past are of interest – since they may give us clues as to what to expect in the future.
Your third choice, Volcanoes by Peter Francis, was published in 1976. Why do you recommend a book that was published over 40 years ago rather than a more recent guide?
This edition of Volcanoes was published as a ‘pocket’-sized Penguin book, and I have fond memories of reading it as a volcano-obsessed teenager. Peter wrote this as a book to be read, rather than as a textbook, and it retains a delightful and timeless quality. I remember being drawn to his descriptions of the magical volcanoes of the high Andes; indeed, so much so that I nearly went to study for a PhD with Peter Francis some years later. His accounts of the three ‘classic’ eruptions — of Vesuvius in AD 79, Krakatoa in 1883, and Mont Pelee in 1902 — are as good as you will find anywhere, with an enthralling mix of eyewitness accounts and volcanological insight.
In volcanology, there is much to be learnt from comparing the eruption ‘of the day’ to case studies from the past, and for this reason Volcanoes is certainly a book to be re-read and enjoyed today.
Your fourth choice is Volcano (2006), a memoir by Yvonne Weekes. Why does this stand out for you?
While there have been many books written about volcanoes as objects of study, as agents of doom, or places of wonder, there are very few that record the first-hand experiences of living with an erupting volcano in your backyard. Yvonne Weekes’s memoir captures the raw dislocation of life on the Caribbean island of Montserrat in the weeks and months after the Soufrière Hills volcano awoke.
“Montserrat has a special significance for me, as it does for many British volcanologists of my generation. ”
When the eruption began, Yvonne was Director of Culture on Montserrat, and a teacher, writer and actor. The energy of the book, which is written in the present tense, carries the reader on an intimate journey through the chaos and uncertainty of the first few years of the eruption. Prior to 1995, Montserrat had not erupted in recorded history. So even though the mountain of Chances Peak had always loomed over the capital Plymouth, it was as if time and the volcano only began on that fateful day in July 1995. More than twenty years later, the volcano is still restless, Plymouth is buried under ash, and the consequences of the eruption are still unfolding for those who lived through it.
Your final choice, Volcano Verses (2003) by Howard Fergus, also relates to the eruption on Montserrat. What does it add to Weekes’s book?
Volcano Verses is a moving and evocative collection of poems that document the trials and tribulations of the ‘infernal volcano’ from 1995-2001. At the time the eruption started, Howard Fergus had been speaker of the Legislative Council for twenty years, and was an historian, poet and lecturer. His poems cross many of the same themes explored by Yvonne Weekes — the waiting, the uncertainty and the inadequacy of the official response to the slow drowning of the land ‘with fiery avalanches, rocks and coffee mud.’ Howard’s perspective ranges from that of pastor to historian; putting the ‘puffs and blows’ of the Soufrière into the context of the island’s colonial past, and religious and cultural present. One fascinating aspect of this collection is the way that the technical language of volcanologists, broadcast daily in radio bulletins, seeps into the fabric of the poems.
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Montserrat has a special significance for me, as it does for many British volcanologists of my generation. In 1998, I spent six weeks on the island on a rotation as staff scientist at the Volcano Observatory. The volcano had just moved into a quiet phase, and the main sign of its existence – behind the cloud cover – was from the occasional dusting of powdery ash that fell to the ground. Fifteen years later, I joined a workshop on Montserrat taking a look back at the eruption and its consequences. It began with an emotional day of stories from those who had lived through the eruption, which made me realise that the narrative of an eruption is not just a timeline of physical events, but the intersection between the live volcano and the people living upon it.
Interview by Caspar Henderson
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