Fire and water PETER FRANCIS

How a new volcanic island failed to change geography, but did change science.

nce or twice in a century, a new volcanic 0 island is born. Pliny the Younger (who also documented the AD 79 eruption of Vesu- vius) provided the first records, reporting that a new island appeared off Santorini, Greece, in 186 BC and that a second popped up close by in AD 19. Over the succeeding centuries, many other islands appeared in other oceans. Most recently, Surtsey rose above the frigid Atlantic waters off the coast of Iceland in 1963, furnish- ing wonderfully atavistic images of new land being born amidst a maelstrom of fire and wa- ter.

A new patch of dry land suddenly appearing in mid-ocean has attractions that go far beyond the merely scientific. On 29 December 1884, Captain Perry of the British steamship Bzrlgar- Fbn reported sighting a submarine eruption halfway between Ireland and Newfoundland. On hearing his report, the British oceanogra- pher Sir John Murray remarked that he hoped that it signified the emergence of a new island, because the Royal Navy needed a coaling sta- tion there. Unfortunately for Murray’s logistic planning, the eruption came to nothing.

A new volcanic island really did break sur- face in 1831, in the Mediterranean south of Sicily. Several European powers were aware of the new island’s potential to command the gateway to the eastern Mediterranean (Fig. 1) - France, Britain, Italy and Spain all laid im- mediate claim to it. It ended up with seven names: Corrao, Ferdinanda, Graham, Hotham, Julia, Nerita and Sciacca. Ch.arles Lyell, the eminent Victorian geologist, had

Fig. 1. Location map of Graham Island, and locations of other reported submarine eruptions in the vicinity.

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some strong views on the seven rival names that the island collected. ‘As the isle was visible for only about three months,’ he thundered, ‘this is an instance of a wanton multiplication of synonyms which has scarcely ever been out- done, even in the annals of zoology and biol- ogy.’ Here, I use one of the two British suggestions, Graham Island, commemorating Sir James Graham, First Lord of the Admi- ralty.

The birth of Graham Island attracted the attention of scholars from almost every learned society in Europe, and their journals carried many accounts of the volcano’s development. These reveal how the eruption profoundly in- fluenced nineteenth-century geological think- ing.

The rise and fall of Graham Island HM ships Britannia and Rapid noted the first unusual developments on 28 June 183 1. While sailing off the coast of Sicily, the ships were jolted by several violent ‘earthquake shocks’, likened to running aground on a sand bank. First signs of actual eruption were reported on 10 July by Captain Corrao of the schooner Theresina. He observed vigorous steaming jets of ‘water’ about 100 m across and 20 m high, which ‘impregnated the atmosphere of its vi- cinity with a sulphurous odour’. Dead fish floated in an area of discoloured water, and there were violent thunderous reports.

On 17 July, the British brig Adelaide re- ported ‘masses of fire’ rising out of the sea to a height of about 100 m. On 18 July, on board the Rapid, Captain Swinbourne saw for the first time new land where only water had ex- isted previously: ‘I saw a high irregular column of very white smoke or steam, bearing S. by E. I steered for it; when having gone about thirty miles, I saw flashes of brilliant light mingled with smoke, which was still distinctly visible by the light of the Moon. In a few minutes, the whole column became black, and larger; al- most immediately afterwards several succes- sive eruptions of fire rose up among the smoke: they subsided, and the column became white again ... flashes and eruption of fire continued at the interval of every half hour. At five A.M., when the smoke had for a moment cleared away at the base, I saw a small hillock of a dark colour a few feet above the sea. The Volcano was in a constant state of activity, and ap- peared to be discharging dust and stones, with columns of steam.’

Later that morning, Swinbourne rowed round the new island, which he found to be a crater with a breach on its south-west side through which the sea surged backwards and forwards. The crater was then about 75 m in diameter, 6 m above sea level at its highest and

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Fig. 2. A lithograph of the Graham Island eruption made from a sketch by an unknown officer on board HMS St Vincent on 6 August 1831, and later sent to HRH the Duke of Sussex, President of the Royal Society. Plumes of white steam rolling steadily upwards from the vent are interspersed with explosively ejected masses of dark ash. Modern volcanologists term this style of eruption surtseyan, commemorating the new island of Surtsey which formed off the coast of Iceland in 1963. A gig from the St Vincent explores at lower left.

2 m at its lowest. It grew rapidly. Four days later, on 22 July, the new island was already 25 m above sea level and about 200 m in diam- eter. As one contemporary account put it, the ‘tremendous efforts of those submarine fires . . . obtained a splendid victory over their formida- ble rivals, the waters of the sea.’

Fig. 3. G. W. Smythe, a cavalry officer aboard HMS Melville, drew the sketch from which this lithograph was made. He was also observing on 6 August, and his sketch shows activity closely similar to that in Fig. 2. In his sketch, the dense plumes of ejecta at centre display a ‘cypressoid’ effect, typical of the violent interaction between water and magma. These plumes are also called ‘cock’s tails’, for obvious reasons.

Seizing the opportunity of a lull in the erup- tion on 3 August, an intrepid officer, Captain Senhouse RN, secured British claims to pos- session by landing on the island to hoist the British ensign. On 5 and 6 August, the fleet flagship HMS St Vincent and the brigs Melville and Ferret were all with a few miles of the vol- cano. Calm, hazy weather meant that the ships could drift lazily, sails slatting idly in the light airs, while their officers took to boats to row nearer the new island. The eruption was near- ing its climax then, building the volcano to a height of more than 60 m above sea level, and a diameter of almost half a kilometre (Fig. 2). Thanks to Vice-Admiral Sir Henry Hotham, commander of the British Mediterranean fleet, the new island was carefully monitored during the subsequent weeks. His officers compiled a chart of the island, complete with closely spaced soundings, showing it to have been irregularly shaped, with a small crater lake at its centre.

G. W. Smythe, ‘cavalry officer in the service of H.M. the King of Sardinia’, watched the fireworks on 6 August from the Melville. He was struck by the contrast between the con- tinuous emission of a white steam plume and violent eruptions of ‘innumerable masses of black cinders and stones . . . propelled with the velocity of lighting from this apparent bed of snow.’ He described these soaring masses of ejecta as resembling ‘a cluster of cypress trees, shooting into existence from a common centre.’ (Fig. 3). Smythe’s is an accurate de- scription of a style of volcanism known as hydrovokanic, or surtseyan, activity by modern volcanologists, for whom the 1963 Icelandic eruption was an ideal opportunity to observe the violent interaction between sea water and magma at temperatures of 1000 “C.

Steady emission of steam to form a tall white column, like that above a power-station cooling tower, is the most obvious conse- quence of hydrovolcanic activity. As fresh bod- ies of magma come into contact with sea water, violent explosions hurl fragmented material up in dark masses, the leading fragments arcing upwards along parabolic paths like rockets, trailing dust behind them. In profile, these jets look something like a clump of fir trees, so vol- canologists sometimes describe them as cypressoid, a striking echo of Smythe’s meta- phor.

This kind of activity continued at Surtsey from 4 November 1963 until April 1964, by which time so much ejected material had piled up on the sea floor that accumulated ejecta in- sulated the hot magma from sea water. Explo- sive interactions between magma and water died away, and were replaced by much less vio- lent, though still spectacular, ejection of glow- ing magma, indistinguishable from that of a

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volcano on dry land. This style of activity is termed strombolian, after the volcano off the north-east coast of Sicily which has been eject- ing gouts of glowing basaltic magma every few minutes for millennia. By the time strombolian activity ceased at Surtsey in May 1965, lavas flowing through a breach in the cone had built a solid island with an area of 2.8 square kilome- tres.

Sadly for Victorian naval strategists dream- ing of re-drawing the map of Europe, Gr. ‘1 h am Island (Fig. 4) never grew as large as Sui-tsey. Its eruption was short-lived, reaching its cli- max sometime between 7 and 15 August I 83 1. On 17 August, when a party of officers from the Rifle Brigade landed, it was merely steam- ing quietly. No subsequent eruptive activity was recorded, and the sea immediately began to reclaim the new island. Graham Island clearly established itself above sea level. For modern volcanologists, though, an intriguing issue is whether or not the eruption ever got beyond hydrovolcanic explosions to aclhieve

Fig. 4. Sketches by G. W. Smythe of the appearance of Graham Island on 6 August in tranquil interludes between explosive outbursts. In the upper sketch, the breach on the west side of the crater-island is plain, with seawater surging in and out. The lower sketch is from a more southerly vantage point, showing the steep sides of the crater already being eroded back by the sea.

the status of a ‘dry land’ volcano, as Surtsey did, because even after a volcano has poked its head above sea level, surtseyan activity may continue if percolation of sea water into the vent has not been sealed off by solid rock.

Circumstantial evidence suggests that it probably did briefly achieve strombolian sta- tus. Smythe described ‘perpendicular torrents of flame’ and ‘a lurid glare of crimson’ showing through the jets of fragmented, chilled ejecta in his ‘cypressoid’ plumes. The way the volcano eroded away, leaving a resistant rocky knoll, also suggests that magma had reached the throat of the volcano without being explosively disrupted. Finally, and most convincing, a gouache painting by an unknown hand, prob- ably executed after 7 August, shows Graham Island in apparent strombolian vigour, with abundant incandescent scoria, and without the dense white steam plume characteristic of hydrovolcanic eruptions (Fig. 5).

Lessons from Graham Island For Charles Lyell, the Graham Island eruption presented a much more fundamental issue than the amount of magma-water interaction that took place. He was one of the leading fig- ures in establishing geology as a science in the mid-nineteenth century, and his book f inci- ples of Geology was to shape much of the think- ing on natural sciences. (It was consulted avidly by Charles Darwin on his historic voy- age around the world.) In Principles of Geology, Lyell devoted much space to a major contem- porary geological controversy, namely, how volcanoes are formed.

Today, this may seem an excessively simple issue, but few eighteenth- or nineteenth- century scientists had the opportunity to see erupting volcanoes. They were thus impressed by what they could see in extinct volcanoes, whose central craters are surrounded by out- ward-dipping beds of lava and scoria. This dis- position led to the notion, espoused in particular by Leopold von Buch (1774-1853), that volcanoes are essentially craters of eleva- tion, formed by the swelling or arching up of the crust of the Earth in response to pressure from below. Strangely enough, von Buch had actually observed a volcanic eruption in Italy, but because the lava streams he saw did not surround the volcano uniformly, he came to the remarkably obtuse conclusion that volca- noes cannot be formed through the accumula- tions of lava flows. Von Buch bolstered his argument with the undeniable observation that many volcanic cones clearly rise from the sea floor to form islands. Such islands could not, he argued, have been formed by magmatic ac- tivity, because this would immediately have been quenched by sea water.

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Many of Lyell’s contemporaries were con- vinced by the craters-of-elevation hypothesis. Some of their arguments still sound plausible today. What is more natural than to suppose that infinite amounts of sea water flooding into a vent would permanently quench subterra- nean volcanic fires? Or that the radially sym- metrical massifs, designated ‘volcanoes’, composed of outward-dipping layers were formed by initially flat-lying strata being heaved up by a central intrusion? There were also plenty of records of vertical movements of the land. At Pozzuoli, near Naples in Italy, for example, the famous marble columns of the Roman temple of Serapis were once far enough below sea level to show evidence of boring by marine organisms. Darwin himself noted the abrupt uplift of land caused by an earthquake that jolted him during his sojourn in Chile.

Lyell did not observe the Graham Island eruption at first hand, but used contemporary accounts to undermine the ‘craters-of-eleva- tion’ theory in two ways. First, the day-by-day observations of the gestation and birth of the island proved that volcanic fires could conquer ocean water. Second, the outward-dipping lay- ered structure described by visitors to the vol- cano coincided exactly with what would be expected from the accumulation of successive layers of ejecta blasted out from a single central vent. Lyell was particularly interested in the question of whether the volcano exhibited both outward dips, on its flanks, and inward, towards the crater. He realized correctly that such inward-dipping beds should be formed in ideal circumstances, but had seen none during a visit to Vesuvius.

Volcanologists now know that beds of ejecta dipping into the interiors of craters are rarely, if ever, preserved in ordinary ‘dry-land’ erup- tions such as those of Vesuvius, because they

Fig. 6. Diamond Head crater, Honolulu, Hawaii: a tuff ring formed by a similar hydrovolcanic eruption to that which formed Graham Island. It is not certain exactly when the Diamond Head eruption took place, but it was probably about 30 000 years ago.

Fig. 5. In this rare gouache painting, white steam plumes and explosive blasts of ejecta are absent, and the volcano is shown in what appears to be a strombolian style of activity, with incandescent gouts of lava being ejected a few hundred metres above the vent. Strombolian activity can only take place when the vent is sealed off from contact with seawater. Neither the exact date of the painting nor the artist is known. [Original in colour.]

are explosively disrupted and reamed out. In- ward-dipping ejecta layers, known as tuff rings, are seen in some volcanoes formed by hydrovolcanic eruptions. A tuff ring, like the famous Diamond Head crater in Honololu, Hawaii (Fig. 6), is larger in diameter than a comparable volcano constructed of ‘ordinary’ scoria, and it is often possible to trace continu- ous layers of ejecta from the centre, over the crater rim, and outwards on to its flanks.

Lyell noted some inward-dipping beds on sketches of Graham Island made on 29 Sep- tember, when it was being rapidly eroded, and queried their nature with his contact, the French geologist, M. C. Prevost. Prevost re- plied that the inward dips were merely artistic licence on the part of M. Joinville, who made the sketches, but to a modern volcanologist’s eye they look plausible. In its eroded state, the profile of the volcano resembles deeply eroded tuff rings, whose inward-dipping beds are sometimes among the last features to be pre- served.

The only other visitor with any claim‘ to sci- entific credentials to visit Graham Island was John Davy, ‘Assistant Inspector of Army Hos- pitals,’ and brother of the luminous Sir Humphry Davy. Davy came close enough to the volcano on 5 August to be enveloped in a thick cloud of ash and vapour so dense that it was completely dark, and he was obliged to hold his breath, expecting the cloud to be hot and acid. When he could hold out no longer, he found, to his surprise, ‘no inconvenience from it.’ He later obtained rock, water and even gas samples from the crater, which he carefully analysed (Fig. 7). His gas analyses must surely be the first ever of volcanic gases, but his main conclusion from them was a nega- tive one: he could not detect hydrogen sul- phide, nor ‘sulphureous acid’, although his nose had told him that they were present. Given the difficulties of sampling volcanic gases even today, his inconclusive results are unsurprising, but his scientific zeal is remark- able.

More importantly for volcanology, he con- cluded, as his brother had previously, that the chemistry of volcanic gases demonstrated that

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Fig. 7. In September, when the eruption had subsided, naval officers made this topographic map of the island, with soundings of the surrounding water. Water from the small crater lake at the centre was collected for analysis by J. Davy, brother of the distinguished chemist Humphry Davy, in some of the earliest chemical studies of volcanic phenomena. Point A was recorded as being 107 feet above sea level at the time of survey. B and C were slightly lower.

‘ordinary combustion was nowise concenned’ in driving the volcanic phenomena, discredit- ing earlier popular notions that purgatorial subterranean fires were responsible. Burning coal seams, naturally enough, had been widely supposed to fuel the fires beneath volcanoes. He also argued that the absence of inflamma- ble gases meant that the heat of volcanism could not have been caused by the ‘decompo- sition of water by the metallic bases of the earths and alkalis.’ Instead, he suggested that ‘our globe having once been in fusion, and still being so at a certain depth below the surface, liable to be acted upon by water flowing in from above, the phenomena of the volcano do not seem to be of difficult explanation.’

A literary finale Once the eruption was over, inquisitive tour- ists swarmed over the island to inspect the mysterious new creation. Curiously, the most celebrated visitor was not a scientist but: an eminent literary figure, Sir Walter Scott. Ap- proaching the end of his long career als a romantic novelist (and President of the Royal Society of Edinburgh, then a worthy rival to its London counterpart), Scott had embarked on HMS Barham to escape the British winter, ex- changing Scottish cold and gloom for Mediter- ranean warmth and light. Sadly, his cruise did little to help his ailing health, for he died shortly after returning to Scotland. On his out- ward journey, however, he was robust enough to insist on landing on Graham Island to ex- plore, on 20 November 183 1.

Finding the going on the soft ash to be ardu- ous, he recruited a stalwart seaman, and toured the island on his shoulders. He col- lected a rock sample, noted that two dolphins had apparently been killed by swimming into hot water near the island, and commented wryly on the body of a robin redbreast that had died on the island ‘where it had neither found food nor water. Such had been the fate of the first attempt to stock the island with fish and fowl.’ On the south side of the island, hot gases still bubbled up through the seawater, tainting the breeze with a brimstone-sharp smell. He wrote a letter describing his experiences, which he dispatched to Scotland to be read before the Royal Society in Edinburgh.

Scott’s account was the last we have. He was lucky to have seen anything of Graham Is- land, which had been eroding away rapidly, or decomposing as he called it in his letter. Con- structive activity had ceased in August. By the end of October, the island was nearly level with the sea, except for a small hill about 60 m high on one side. This was still visible when Scott landed in November. By the end of December, it had disappeared, leaving only a small rock projecting above the sea. This, too, was soon washed away, leaving only shallow, discol- oured water to mark the site of the volcano.

So Graham Island came to nothing. Al- though it survived only a few months, it left a lasting mark on volcanology and the history of science. And although no island grew in 1831, there is plenty of reason to suppose that a new island will appear in the Mediterranean in the future. Submarine eruptions were reported off Sicilyin 1845,1846,1863 and 1891. Onedaya new volcanic island will probably emerge be- tween Sicily and Libya, one that will endure. It will be instructive to see who claims it, and how many names it acquires.

Suggestions for further reading Francis, Peter. 1993. Volcanoes: A Planeta y

Perspective. Oxford University Press, Ox- ford. 443pp. (A general overview of the modern field of volcanology.)

KrafTt, Maurice. 199 1. Volcanoes: Fire from the Eurth. Thames and Hudson. 207pp. (An excellent and beautifully illustrated little book on the history of volcanology.)

Poulet Scrope, G. 1862. Volcanoes: The Char- acter of Their Phenomena. Longman, London. 490pp. (One of the classics in vol- canology, this book provides a fascinating Victorian perspective on volcanology, and the eruption of Graham Island.)

Peter Francis is Reader in Earth Sciences at the Open University

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