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Gunung Tambora
A big vulcano that erupted in the 19th century

The paroxysmal eruption of Mt. Tambora on the island of Sumbawa in April 1815 – despite having triggered a world wide historic event – is astonishingly neglected in studies of volcanic activity. The world wide event referred to was the so-called "Year without a Summer" - the exceptionally cold months of 1816. In addition to this, Mt. Tambora's eruption far-eclipsed in violence and ejecta the more famous eruption of Krakatau (Krakatoa) in 1883, which also had an impact on the world's weather.
Though disappointing, the reason for part of this neglect is not hard to find. There exist few contemporary records of the eruption and what there is has seen little reprinting in modern works. Nonetheless, enough data is now available that a more definitive study can and should be undertaken. The intent of this posting is to synthesize and integrate what is available and hopefully inspire further investigation.
Sir Thomas Stamford Raffles, later founder of Singapore, was at the time of the eruption serving as Lt. Governor of Java, based at his capital in Batavia. He had occupied this post since September 1911, a month after the British had wrested Batavia from control of Napoleon's France. Having heard of the great human distress and disastrous phenomena accompanying the outbreak, he gave orders that British residents gather information and report if possible to him on the effects of the eruption On April 18, Lt. Owen Phillips was dispatched with a shipload of rice for relief to the disaster zone. It is from Phillips' findings, and Raffles subsequent submission of his report to the Natural Historical Society of Batavia in September 1815 that we learn after-the-fact of the details of the eruption. It is important to note that no native accounts save one are known to survive, and the character and form of the eruption must be reconstructed "retroactively" working backwards from the Raffles report and the physical aftermath on the islands. With this challenge in mind, we proceed.

The eruption

Even allowing for the scant documention, the characteristic about the eruption that immediately jumps out at the researcher is its terrifying speed and brevity. When this is contrasted with its stupendous scale and effects, the event becomes a singularly sobering and daunting one. Perhaps only the Mt. Tarawera eruption of 1886 in New Zealand compares in modern times for sheer suddenness and destructive force of eruption. A word of explanation is in order here. Though such celebrated eruptions as Krakatau, Mt. St. Helens, Mt. Pelee, and more recently El Chichon and Pinatubo, capture the public eye and respect, all of those powerful eruptions had fairly lengthy eruptive sequences. In short, for those with mind to do so, there was ample time if not always means to vacate the danger zone. With Tarawera it was different---in 1886 in the space of one night a triple peak mountain range near Lake Rotomahana suddenly split open and erupted. Literally some 4,000 people who had gone to their beds that evening would never again wake up. Such a disastrous and only slightly less deadly suddenness accompanied the Tambora eruption.

The Setting

Almost nothing is reliably known about the form and history of Mt. Tambora prior to the 1815 eruption. (Some indication of the lack of exploration of the region is gained by noting that the famous Komodo Dragons on the adjacent island of Komodos were only discovered in 1911!). However, mountains being what they are, the remnants tell a great deal to the expert eye. Although the top of the mountain collapsed in 1815, what still stands is unusual and provocative in its features. According to the best available evidence, before the eruption Mt. Tambora was a volcanic cone 4,000 meters high and 60 kilometers in diameter at sea level; densely blanketed in forest. It is reported to have originally had two summits, and there were several parasitic cones on the east and northeast slopes. What is unusual is that studies indicate that in its first phase of activity Tambora was a shield volcano, not unlike those of Iceland or Hawaii. Later, a bedded cone was built up on top of this, possibly the result of a change in the composition of the magma. The mountain, which may well have begun life as an island separate from Sumbawa, in time rose to dominate a peninsula joining it to Sumbawa on the southwest flank. By the time the Europeans came to occupy Sumbawa in the 18th century Mt. Tambora had lapsed into a deep dormancy. This state of affairs continued for a decade more into the 19th century. Then the volcanic energies once again burst forth.
At the time of the Tambora eruption, some 140,000 natives were reported to be living on Sumbawa. Sumbawa is long vaguely rectangular island running nearly from west to east. About a third the way from the eastern end, on the north side, a large peninsula projects northwestward like the trigger of a gun. But this trigger belonged to a cannon capable of force like no general of the age could ever have imagined. For it is on this penninsula, the Sanggar Peninsula, that Mt. Tambora stands. Scattered around in 1815 some 12, 000 people lived in a handful of villages and towns clustered on the peninsula of Tambora. Forty miles to the eastward, a small British contingent headed by a Resident resided at the village port of Bima, the capital of the European colonists. Bima was located beside Bima Bay, a deep indentation in the northern side of the east end of Sumbawa, and about 40 miles east of Tambora's peninsula.
Though some mild spewings of ash were alleged to have occurred at the summit in the spring of 1814, the first real and almost only warnings were a rolling succession of deep shocks through the Dutch East Indies on the evening of April 5. In Dutch Macassar the warship Benares of the East India Company lay at anchor, the officers and crew perturbed by what seemed to be a naval battle taking place just over the horizon to the south. As dusk neared, the barrage seemed closer, with heavy artillery seemingly sprinkled with intermitent rifle volleys; just then a detachment of troops arrived aboard, and the Benares was ordered to put to sea to investigate. But they found nothing nor the source of the "cannonade", although they remained at sea for three days. In the words of a modern author, "that was just as well. For if they had, there was nothing they, nor all the troops and ships in the world, could have done about it." Indeed, for their quarry was no pirate over the horizon: but more than 200 miles south, and what was fast becoming the most explosive eruption of recorded history.
With sunrise on April 6 light ashes began falling on Batavia. The sun became obscured in the skies over Java, "having the appearance of being enveloped in a fog. The weather was sultry and the atmosphere close, and still the sun seemed shorn of its rays, and the general stillness and pressure of the atmosphere seemed to forebode an earthquake. This lasted several days." Oddly enough, the rumblings and explosions – though they continued – now seemed to come less frequently and with less noise. The Europeans were perplexed and concerned, but some of the Java natives, however, were delighted: priests declared with confidence and satisfaction that the thunder and dark was the sign that the gods of the mountains were coming forth to free the island from foreign rule. However as the ash fall grew and persisted, while the rumblings and explosions continued, all those in-the-know now realized it must be a volcanic outbreak, and the speculation was that Merapi, Kelut, or Bromo was the likely culprit. With the cause if not the source of the disturbance identified, the Europeans at least became less concerned and ceased to pay much attention to it, for this volcanic outbreak was not yet "considered of greater importance than those which have occasionally burst forth in Java".
This educated complacency abruptly shattered on April 10. As if rebuking their hubris, as the afternoon came, suddenly the roar and detonations like blasting gravel and cannon renwed, even stronger than before, and this time a truly menacing and darkened cloud of ash billowed over from the east. This time it was even greater than before, so that the sun was almost blotted out. In the eastern part of Java, the situation was even more severe. At Solo and Rembang some reported small and continuous earthquakes, and the explosions were tremendous, booming frequently through the 11th with such violence as to shake the houses noticeably. And still the might of the detonations only increased, and the . Once again the priests sang with joy that liberation was at hand, and even some of the Europeans now felt fear and concern. What was happening? None of the suspected volcanoes were known to be in eruption, and yet almost 2,500 miles of island chain was being rocked by cataclysmic quakes. Not a few must have contemplated the fate of Pompeii and Herculaneum---buried by Vesuvius in AD. 79 – but there was little anyone could do but wait. These were the conditions on Java and neighboring islands as dusk approached on April 10. But for those living on the peninsula upon which Tambora stood, matters would grow much worse this night. For in the late afternoon of the 10th Mt. Tambora in fact entered paroxysmal eruption and would inflict a devastation that would leave precious few survivors to tell the tale.
Fortunately, despite the primitive conditions prevailing on the island, via Lt. Phillips, we do indeed possess one eyewitness account from the Rajah of Sangir. Sangir was on the north shore of Sumbawa, just to the east of Tambora's peninsula, less than twenty-five miles from the summit. The Rajah was in his village at the time of the eruption, he told Phillips, and in fact witnessed its climatic acceleration and effect. As such, his report is incredibly valuable. Moreover, allowing for the inexperience and comprehension of the witness, the Rajah of Sangir's words show – to the volcanologist – a remarkable and likely trustworthy immediacy and clarity. He stated that "about 7pm on the 10th of April, three distinct columns of flame burst forth near the top of Tomboro mountain (all of them apparently within the verge of the crater), and after ascending to a very great height, their tops united in the air in a troubled and confused manner." The words "troubled and confused manner" are a singularly vivid and accurate description of the volcanic ash clouds that boil upward from paroxysmal eruptions. He next says "In a short time, the whole mountain next to Sangir appeared like a body of liquid fire, extending itself in every direction. The fire and columns of flame continued to rage with unabated fury, until the darkness caused by the quantity of falling matter obscured it at about 8pm." Hence, within an hour of the primary outbreak, the falling ash has obscured the summit from view. This too is consistent with such eruptions, and vouches for its reliability. The "liquid fire" is almost certainly pyroclastic surges rather than true lava flows, but this point cannot be proven.
As the Rajah and his people watched in consternation, "stones" (volcanic bombs and lapilli) began to fall on Sangir, "some of them as large as two fists, but generally not larger than walnuts". Between 9 and 10pm ashes began to fall, and "and soon after a violent whirlwind ensued which blew down nearly every house in the village of Sangir, carrying the ataps, or roofs, and light parts away with it. In the part of Sangir adjoining [facing] Tomboro its effects were much more violent, tearing up the roots of the largest trees and carrying them into the air, together with men, horses, cattle, and whatever else came within its influence. The sea rose nearly twelve feet higher than it had ever been known to do before, and completely spoiled the the only small spots of rice land at Sangir, sweeping away houses and everything within its reach. The whirlwind lasted about an hour. No explosions were heard till the whirlwind had ceased, at about 11pm."
Whatever atmospheric phenomena caused the absence of explosion sounds during the whirlwind, it ended with it. Starting about an hour before midnight, stupendously loud explosions were heard, "from midnight to the evening of the 11th, they continued without intermission"! Given the conditions prevailing in Sangir, the plight of the villages actually on Tambora's flanks and the peninsula could only be imagined. In fact, they were scenes out of the end of the world, with "great tracts of land being covered by lava, several streams of which", issuing from the summit of the disintegrating mountain "reached the sea." In several places, whole portions of land suddenly subsided, and were swallowed by the inrushing sea.
The blanket of ashes was so heavy that they collapsed the roofs of the Resident's and many other dwellings in Bima and rendered them uninhabitable. The Dompu Palace at Dora Bata was also buried with ash. At Bima the thickness of ash was later found to be one and a half feet deep, but at Sangir much nearer to the volcano it was three feet deep. "Although the wind at Bima was queerly still during the whole time, the sea rolled in upon the shore, and filled the lower parts of the houses with water a foot deep. Every boat was forced from the anchorage and driven on shore." All around Sumbawa the neighboring islands reported similar odd pheonmena, as "the sea rose suddenly to the height of from two to twelve feet, a great wave rushing upon the estuaries, and then suddenly subsiding." On the adjacent island of Bali, the ash lay a foot deep as well.
Throughout the night of the 10th and through the day of the 11th the mountain raged with an incredible fury and violence. As if sending a warning to the growing confidence and pride of western man, Mt. Tambora roared with an unbridled and unmatched defiance that rocked the entire East Indies. An eruption column of ash and dust boiled an incredible 28 miles into the sky, as lightning danced with the fury of dervishes amidst it.
The enigmatic detonations began again on the afternoon of April 11, and this time houses and buildings in Macassar began to actually shake. The warship Benares put to sea, heading southward to investigate. However, by noon on the 12th the sky had become almost opaque and almost filled with fine ash. Daylight was scarcely visible, as a stygian darkness descended. Native village shamans proudly and confidently declared that the old gods had burst forth and were about to drive the Europeans from Indonesia. As it happened, nothing of the sort occurred, and after three days the skies gradually brightened again. The thundering ceased abruptly.
Finally the eruption's fury began to wane late on the 11th, the sharp and loud detonations moderating and "heard only at intervals". But on the 12th far to the west of Sumbawa, floating pumice still formed a mass two feet thick and miles in extent! So thick was it that ships had difficulty breaking through the drifting mass.
In Java, the "haziness and heat of the atmosphere, and occasional fall of volcanic ashes, continued until the 14th, and in some parts of the island until the 17th of April". However, the Javanese were lucky: heavy and timely falls of rain ensued, helping to wash away the ash and clear the sky so that severe injury to crops and outbreaks of epidemic were avoided. Alas for the Sumbawans, there would be no such reprieve.. At last, on July 15, 1815, the last explosions ceased. The skies cleared, and revealed was a Dantesque panorama of destruction and ruin.
On Mt. Tambora, the once irregular and lofty summit had been lopped off, as if with a knife, forming a flat-topped massif capped by a stupendous caldera. Given the low-order of eruptions since 1815, modern figures are probably very close to those of 1815, with little change to the mountain since: The eruption had formed a caldera 6 kilometers in diameter and 1,110 meters deep. The highest point was (and is now) 2,850 meters above sea level.
The loss of life and destruction was appalling. Of the thriving village-towns in the province of Tomboro near the mountain, comprising some 12,000 inhabitants, only small Tempo and its forty inhabitants remained. All the others had been obliterated by whirlwinds or engulfed as frightening subsidences of land occurred. No trace remained of the villages of Tomboro and Pekate, and "no vestige of a house" was left. During the eruption, the town of Tomboro on the west side of Sumbawa had been "overflowed by the sea, which encroached upon the shore so that water remained permanently 18 feet deep in places where there was land before." Only five or six from both towns were known to have even survived. Of the others only twenty-six badly burned people of a party out from Pekate managed to paddle their canoes away from the peninsula and survive. The devastation was concentrated on the north and west sides of the peninsula of the mountain, the "trees and herbage of every description, along the whole of the north and west sides…" had been "completely destroyed, with the exception of a high point of land near the spot where the village of Tomboro once stood." Out at sea, there was huge mass of floating trees littering the surface of the water for miles around the peninsula.
Nor were conditions much better in the eastern part of the island around Bima. Famine of extraordinary and severe intensity broke out, taking the lives of thousands. Having arrived on Sumbawa and writing from Bima about August 3, Lt. Phillips reported: "The extreme misery to which the inhabitants have been reduced is shocking to behold. There were still on the road side the remains of several corpses, and the marks of where many others had been interred; the villages almost entirely deserted and the houses fallen down, the surviving inhabitants having dispersed in search of food." The famine was so severe in Sangir, Phillips reported, that even one of the Rajah of Sangir's [the learned eyewitness who described the eruption above] own daughters had died from hunger. Phillips gave the man three coyangs of rice, for which he was most thankful, but such help paled before the disaster engulfing the Dutch East Indies.
For the ash cloud covered and destroyed crops throughout the archipelago, giving rise to insects that destroyed the plants at the root. Mass famine broke out, and on Lombok Island the ash killed everything growing on the island. With all vegatation dead, the majority of the island's inhabitants of 37,000 people died of starvation.
The eruption of Tambora even had a less well-known, but not insignificant impact on literature. In the summer of 1816, the nineteen-year old writer Mary Godwin (soon to be Shelley) was staying at Lake Geneva at that time having previously eloped with future-husband Percy Shelley, and they were now with no less a luminary than Lord Byron and his physician John Polidori. In the past, Voltaire and Rousseau had come to these shores, and the region was widely regarded (and would be later, with Carl Jung) as a sacred place where enlightenment would come to those who seek it. To the perplexed group at that time, the previously beautiful weather turned tumultous and stormy in June. They did not learn of it till later, but they were experiencing the effects of mighty Mt. Tambora's historic eruption on the other side of the world. On June 16th, 1816 the group was prevented from returning to town from their lakeside villa by a powerful storm. Such weather in June was unheard of, and the entourage took to reading German ghost stories, and inspired, Byron challenged each member to come up with one of their own. In response, John Polidori commenced the Vampyre, the first modern vampire story. The others wrote some forgettable breifs. However, five days later, with the bizarre lightning streaked summer nights continuing, Mary was inspired by a discussion of whether a corpse could be animated by science. That night she had a "waking nightmare" and the next morning, she began to write her story inspired from it. The work was completed in the following year, and became known to the world as ….Frankenstein. Realizing the volcanic-induced haywire weather of that June was unique, she changed her season for her tale and wrote "it was on a dreary night in November…." Hence, behind each depiction of the birth of Frakenstein's monster there lies just a little bit of the real pyrotechnic awe and terror of the eruption of Tambora!

The nature of the eruption

From the foregoing it is immediately seen that the Tambora eruption is exceptional for its ferocity and rapid acceleration to full climax. Despite the over-use of the example by popular literature, in this case it is indeed useful to compare it to the eruption of Mt. Vesuvius in 79 A.D. The outbreaks share notable similarities: [1] a fairly short-term series of pre-monitory quakes, [ 2] a heavily wooded and long dormant volcano that like Vesuvius, seems to have a hybrid basaltic and andesitic charcter---possibly having like Vesuvius risen originally from under shallow waters and joined to the island by peninsula. [3] a paroxysmal "clearing of the vent" eruption cloud that sent a large cauliflower skyward, [4] a rapid descent of darkness from a falling ash cloud, [5] the appearance of localized, possibly identical "base surges" fanning out from the disintegrating cone, [6] and an accleration through paroxysmal eruption and climax in the space of less than 72 hours, followed by a rapid tapering off of activity.
It is just possible that Tambora triggered a partial collapse of itself early in the eruption, unleashing an eruption plume of sudden and horrific force, not unlike Mt. St. Helens in 1980. The reason for suggesting this is in the sheer power and velocity of the eruption column, as well as its fairly short duration. It appears to point to a fairly sudden, preciptous rather than a steadily mounting release. But this is merely informed speculation, and though interesting, is impossible to verify at present.
No later than April 5, but possibly earlier, Tambora was shaken by a "throat-clearing" eruption that punched a new vent in the summit and cast forth a volley of ash over the Flores Sea. Though the eyewitness accounts describe only the climatic phase of the eruption and not the preliminaries, it seems impossible to assume that the Sumbawans were unaware that Tambora was now active. Possibly being experienced with neighboring Bali andLombok's eruptions, they did not think it too serious at first. Or possibly evacuating was not a particularly practical option for most. In any case, most inhabitants of Tambora's peninsula remained where they were as the eruption grumbled on into April 6. By sunset of the next day, the activity apparently faded, nearly to a halt, though the rumblings continued. Perhaps this lulled any doubts the people may have had. The eruption appeared to be waning, and few sought to flee the mountain's fertile environs. Whatever circumstances prompted this choice, it sealed the fate of 90% of the inhabitants.
For as afternoon waned on April 10, the rumblings in the mountain grew loud again, and as the sun touched the horizon and dusk fell, three tremendous incandescent plumes left forth from the summit. In minutes these grew to a towering nimbus cloud of ash and lightning that drew a dark curtain over the night of death that followed as the titanic paroxysm reached its climax. Incredibly explosive, evacuating its chamber with manic speed, Tambora hurled its bowels into the night sky. Quaking with Vesuvian force and fury, the cone began to come apart and subside into the growing void below. As it did so, numerous pyroclastics flows lashed out from the ash column as it collapsed, rushing down valleys, annihilating everything in their path to meet the sea with thundering steam explosions. (It is tempting to speculate that these "lava flows" were in actuality the deadly nuee ardentes characteristic of Carribbean and Indonesian volcanoes and unrecognized until the 1902 Mt. Pelee eruption. Such "glowing avalanches" or "hurricane blasts" are common to a a caldera-producing eruption and would go far to explain some of the unusual and severe effects reported.).
How powerful was the Tambora eruption? Such questions can be misleading, but by any scale one chooses to measure the 1815 eruption of Tambora was one of the mightiest and deadliest in history. On the Volcanic Explosivity Index (VEI), Tambora rates a 7, one of only four in the last 10,000 eruptions to do so. For comparison, the famous Krakatoa blast was VEI 6, and the recent Mt. St. Helen's blast of May 1980 was VEI 5. Tambora was in a class all its own. Some understanding of this may be gained when one discovers the definition of Krakatoa's Category 6 is "colossal"----whereas Tambora's 7 necessitates the word "super-colossal"! (Category 5 of St. Helens means "paroxysmal"). The eruptive type is judged to have been "Ultra-Plinian", in other words a mega-version of the outbreak of Vesuvius that gave its name to the type and destroyed Pompeii and Herculaneum and 3,360 lives.

Aftermath

After the eruption, more than 1,000 meters of the mountain's height collapsed or was obliterated, with the result that a caldera nearly six kilometers in diameter whose rim was 2,950 meters above sea level was formed. A scientific expedition led by a Swiss Botanist named Heinrich Zollinger arrived at Sumbawa in 1847 to study the eruption scene and its effects on local fauna. The decapitated mountain was still smoking as they ascended the east flank of the mountain. As Zollinger climbed, here and there his feet would break through a thin surface crust into a warm layer of powder-like sulfur. When he reached the top Zollinger became the first human known to visit the summit, though he spent little more than an hour there. He was astonished by the yawning crater he found before him, more than three miles wide, and by making a calculation on when a pan of water he had boiled, determined that the highest rim of the caldera (that word was not yet in use however) was now only about 9,000 feet above sea level. Given some of the reports received from the natives about its former stature, this mean that 4,000 feet of mountain had been somehow destroyed, seemingly blown to atoms. Awed by the discovery, Zollinger descended the mountain and continued to study the radius of the ash fallout and eventually produced a map. Of course, though he could not know it, Tambora had been "engulfed" by caldera collapse, and not annihilated, but a full century would pass before geologists would fully appreciate this phenomemena.
Though the mountain appeared to be quiet, such was not the case. Some time between the great eruption and 1913, when it was next visited, Tambora must have awakened again. For in the southwest part of the caldera bottom a 100 meter wide and 60 meters deep crater opened, and from it snaked forth a 350 meter long lava stream, moving like a flow of slag across the caldera. Despite this fairly large activity, the existence of this new vent was not suspected or discovered until 1913 when a Dutch team headed by J. Elbert visited the summit. They discovered the crater and named it "Doro Afi Toi" as well as noted the remains of another secondary crater near the southern caldera wall and what appeared to be sand-covered lava plugs dotting the floor. Clearly Tambora Caldera remained considerably active after the period of the grand collapse, though apparently its fumings had not disrupted the tranquility of the inhabitants below enough to be noticed.
Though the Japanese occupied Sumbawa in World War II, no notice was taken of the volcano, or activity reported. The only noteworthy event was the sinking of light cruiser Isuzu just outside of Bima Bay in April of 1945. However, just after the war, exactly one hundred years after Zollinger's survey, geologist W. A. Petroeschevsky visited the caldera in 1947. Over a two day period he walked around the rim (though he did not descend into the caldera) and described grass, sulphur deposits, small craters and vents on the bottom. In addition, for the first time the existence of a freshwater lake fed by rains was mentioned. It existed in the bottom of the caldera, with a group of trees sprouting beside it. This phenomena is far from unusual, and occurs in other cataclysmic caldera-forming eruptions. Mt. Katmai in 1912, Mt. Coseguina in 1835, and the famous `Crater Lake' of Mt. Mazama are just a few examples. It has been suggested that such post-eruptive lakes might even originate from within the mountain, but this is an open question.



    
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