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Vol. 21
March Issue
Year 2020
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Off the Beaten Track


in Vol. 21 - March Issue - Year 2020
The Year Without A Summer



Mount Tambora as it appears today


Caspar David Friedrich - View of a Harbour

The rich black earth yielded bountiful harvests and livestock found plenty to eat in the luscious green fields. The locals could hear the rumblings and see the plumes of black smoke that occasionally rose from the mountain towering over their villages. The explosions had been getting louder in the past weeks and flames were shooting into the air at night. Every so often the farmers would straighten up from their plows and glance nervously at the mountaintop.

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Mount Tambora is a volcano on the Indonesian island of Sumbawa. On the evening of 10 April 1815, the entire mountain exploded in what is the most powerful volcanic eruption in recorded history. This catastrophic event caused climate change, the collapse of agriculture, and pandemics around the world. It even indirectly influenced some forms of art in Europe. To this day, scientists are still struggling to fully understand its repercussions.
Tambora had been dormant for thousands of years, but in 1812, a series of minor earthquakes, explosions and ash emissions signaled its awakening. For centuries before then, a humongous mass of magma, together with about 6% of water, had accumulated in the volcano’s chamber at depths between 1.5 and 4.5 kilometers. This viscose fluid reached a temperature of about 1,000°C at pressures up to 5,000 bar. The peak of the mountain reached a height of 4,300 meters, making it the tenth tallest mountain in the world at that time.
A large explosion occurred on 5 April 1815, a few days before the main eruption. It was followed by a series of thunderous detonations that were heard in Jakarta, 1,260 km away, and on the Molucca Islands, 1,400 km away. Sir Stamford Raffles, then Lieutenant Governor of the Dutch East Indies and the future founder of Singapore, recorded the event in his memoirs. “The noise was, in the first instance, almost universally attributed to distant cannon; so much so, that a detachment of troops were marched from Jogjakarta, in the belief that a neighboring post was being attacked, and along the coast boats were in two instances dispatched in quest of a supposed ship in distress.”
Volcanic ash fell and the rumblings continued for the next ten days. Then, at around seven o’clock on the evening of April 10th, Mount Tambora erupted with unprecedented violence and power. Witnesses described three flaming columns of lava rising hundreds of meters in the air. Pyroclastic flows, made of molten rock and hot gases reaching temperatures of 1,000°C, raced down the slopes of the volcano at speeds of up to 700 km/h. Hot air generated by these pyroclastic flows rose rapidly, creating a vacuum into which cooler air rushed with such force that trees were uprooted and people and animals were swept away. Four-meter high tsunamis slammed into surrounding islands. The cloud of ash turned days into nights and smothered crops. An estimated 100,000 people died on the islands of Sumbawa, Lombok, Bali and Java as a direct result of pyroclastic flows, tsunamis and post-eruption famine and epidemic diseases.
The 1815 eruption of Mount Tambora continued for weeks and ejected 100 cubic kilometers of ash and gases to an altitude of 43 kilometers, making it the only eruption in recorded history to be classified VEI-7. The Volcanic Explosivity Index (VEI) assigns indices from 0 to 8, depending on how much volcanic material is ejected, to what height and how long the eruption lasts. In addition to millions of tons of ash, Tambora ejected about 55 million tons of sulfur-dioxide gas into the stratosphere, where it combined with hydroxide gas to form 100 million tons of sulfuric acid. This combination condensed into an aerosol cloud with fine dust particles that remained suspended in the air for up to three years, blown around the globe by the strong stratospheric jet streams.
The Tambora aerosol cloud caused average global temperatures to decrease by about 0.4 to 0.7°C, with drops of up to 3°C in some areas. It provoked severe disruptions in weather patterns and wreaked havoc on agriculture from Asia to Europe and as far away as the eastern coast of North America. Some countries suffered famine and pandemics. The year 1816 was the second coldest in the Northern Hemisphere since the 1400s and was thus dubbed “the year without a summer”.
This event produced some interesting optical phenomena. Artists such as Turner, Constable and Friedrich included the reddish-orange glow of the sky over England in 1815 and 1816 in many of their most famous landscape paintings.




Author: Giovanni Gregorat
By Giovanni Gregorat, Contributing Editor MFN