Mount St Helens, Verusvius, Krakatoa; humanity has witnessed some pretty explosive eruptions that have changed how we view our planet. However these have been nothing compared to the large caldera forming, ignimbrite eruptions or flood basalts of the past. The closest humans have seen to the elusive ‘super eruption’ occurred 200 years ago on the Indonesian island of Sumbawa, and it changed our view on volcanics for all time.
Up until the early 1800’s the mountain of Tambora, although towering roughly 14,000 ft over the surrounding area, seemed a rather nonthreatening feature of the landscape. No eruptions for hundreds of years meant few locals even knew it was of volcanic origins. The British East India Company had not long laid claim to many of the Indonesian islands when this began to change around 1812. The foreign residents knew little of the Earth’s more violent activity and even natives paid little attention to an increase in seismicity and small phreatic eruptions and minor ash emissions.This is what made the events which began April 5th 1985 all the more deadly.
Figure 1. An artist impression of the eruption on April 5th.
Thomas Stanford Raffles was at the time the lieutenant governor of Java. Although of a political position he had a keen scientific mind and brought in zoologists and botanists to the islands as well as making his own observations and recordings. He was, in his own right, one of the first true volcanologists, being the first to scale a volcano using a thermometer to measure differences from base to peak. On April 5th he was over 800 miles away from Tambora when things really began. At just after 7 pm as people settled down in to their evenings Tambora let out and immense roar. Raffles, like many, recorded hearing ‘cannon fire’, troops were even deployed from Djogjokata to seek out potential threat at sea. When ash began to lightly fall by the next morning Raffles sent out parties to find the source of the eruption. Klut, Merapi or Bromo were thought to be the most likely culprits being highly active and close enough to cover the area in ash, Tambora was not even considered. As the days went on and the ash fall waned so did the search and things settled down with the volcano momentarily. The initial eruption only last two hours and ash fall a few days. Sadly this did not last….
It soon became apparent that the eruption on the 5th was purely Tambora clearing her throat and preparing for a much bigger song. On April 10th 3 epic blasts from areas near the summit sent material 40 km in to the sky, meeting to produce a spectacular eruption column. Eventually the three vents caused a huge collapse creating the 6-7 km wide caldera still visible today. Pyroclastic flows sped down the flanks destroying everything in their path. The flux of material pouring in to the Flores sea to the caused a tsunami that rapidly spread through the surrounding waters and islands with waves up to 6ft high. Within 3hrs the sky was invisible for miles, as far as West Java and South Sulawesi. The loud explosions were heard through to the next night showing little sign of easing for over 24hrs.
Figure 2. Path of the ash cloud. Most of the red area was in complete darkness while the eruption was persistent and for days after.
The eruption did not settle down until April 17th, with the summit completely obscured by an ash cloud untill the 23rd. Explosions although smaller, did not cease untill July 15th, and smoke emissions were still observed as late as August 23rd.
Figure 3. Out put of several major eruptions in recent history.
Tambora lost at least 2000 ft off its summit equating to it loosing nearly a third of its original height. It is believed to be the only VEI 7 eruption of our time (luckily for us!). The VEI index is a logarithmic scale meaning each level is ten times that of the previous. Based on eruption output the graph in figure 3 shows just how big this eruption was. Thanks to Pompeii, Versuvius’ 79 Ad eruption is probably one of the most famous eruptions but even this killer pales in magnitude compared to Tambora’s might! The explosion was 800 Mt (3.3×1012 MJ), four times the energy of Krakatoa and would make even an atomic bomb look like dropping a pebble in an ocean. Rafts of pumice up to 5 km across caused havoc on shipping lanes and even crossed the Indian ocean washing up on Calcutta 6 months after the eruption began. It is believed at leat 12,000 were directly killed by the eruption through pyroclastic flows. Add to this the tsunamis and devastation to the land which brought famine and disease bringing an estimate of 72,000 – 100,000 fatalities caused by the eruption.
Since the eruption, a violent diarrhoea has prevailed in Bima, Dompo, and Sang’ir, which has carried off a great number of people. It is supposed by the natives to have been caused by drinking water which has been impregnated with ashes; and horses have also died, in great numbers, from a similar complaint.
But it was not just the local area which was effected by the blasts, Tambora brought on what is famously known as The Year Without a Summer. As well as pyroclastic material the eruption injected a massive amounts of sulphur dioxide and other volatiles not just in to the atmosphere but they were catapulted in to the stratosphere. This caused globe climate chaos for several years. The Northern Hemisphere got the brunt of the bizarre weather such as frost in June and some of the most spectacular coloured sunsets ever recorded.
Crops failed world wide and famine was riffe in many areas. It is believed the climate change brought on by Tambora attributed to 90,000 extra deaths over the years after the eruption. Although the weather had many negative effects it inspired many and was indirectly recorded in many notable artist such as Willam Turner and poetry like Lord Byron’s Darkness. Even literature was influenced as Mary Shelly’s backdrop to Frankenstein mirror the climate caused by Tambora.
“I had a dream, which was not all a dream at all
The bright sun was extinguish’d, and the stars
Did wander darkling in the eternal space,
Rayless, and pathless, and the icy earth
Swung blind and blackening in the moonless air;
Morn came and went–and came, and brought no day,
And men forgot their passions in the dread
Of this their desolation”
Lord Byron Darkness
When Krakatoa erupted in 1883 it was the first eruption to make world-wide news as the telegraph made it more accessible. Such technology was not available in 1815 so news of tragedy in Indonesia only travelled as fast as the best ship. Even for people who did know about the events no link was ever made to the weather conditions which plagued the world. Unlike Pompeii’s early discovery pushing it to the limelight, it was only in 2004 that archeologists found remains of villages buried deep under the deposits Although excavation still takes place in the area it is believed they have barely scratched the surface.
Figure 4. Finding in 2004 if remains from a village destroyed by a pyroclastic flow.
We don’t know if or when Tambora will blow her top again, we don’t know if further eruptions from her or any other of the 150 volcanoes in Indonesia will erupt so violently or even worse. What we do know is that we live on a violent, dynamic planet which is beyond our control. We need to learn from eruptions of the past, and to read precursors to such events to limit their effects on humanity so we have a chance for surviving the next big one.
Figure 1. http://madmikesamerica.com/2011/09/terrified-farmers-flee-ahead-of-deadly-volcano-eruption/
Figure 2. http://commons.wikimedia.org/wiki/File:1815_Tambora_Sumbawa_explosion_path_large.jpg
Figure 3. http://legacy.earlham.edu/~ethribe/web/tambora.htm
Figure 4 http://www.pasthorizonspr.com/index.php/archives/11/2009/re-discovering-the-lost-kingdom-of-tambora