Mount Tambora

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Mount Tambora is a stratovolcano on the Indonesian island of Sumbawa. In 1815, the volcano of Tambora suffered the most violent eruption in modern times. Beginning in early April and continuing through the middle of July, its explosion affected an immense area that included the Maluku Islands (Molucca Islands), Java, and portions of Sulawesi (Celebes), Sumatra, and Borneo. Heavy ash rains also specifically affected the islands of Bali and Lombok. Approximately 92,000 people were killed because of pyroclastic flows or starvation and disease. 1816 became known as "the Year Without a Summer" because of the extreme weather conditions the eruption caused as far away as North America.

1 The most violent eruption in recorded history
- 1.1 Effects
2 Quotes from 1815 accounts of the eruption
3 See also
4 References
5 External links

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The most violent eruption in recorded history

Mount Tambora erupted on April 10, by most accounts, and the eruption lasted from April 10 to April 15. The explosion, of Volcanic Explosivity Index 6-7 released roughly 4 times the energy of the 1883 eruption of Krakatoa and it ejected an estimated 100 cubic km of pyroclastic trachyandesite, weighing approximately 2-3 × 10¹⁴ kg. This left a caldera 7 km (4 mi) across. Before the explosion, Mount Tambora was approximately 4200 m (13,000 ft) high; after the explosion, it was only 2851 m (about 9,000 ft) high.

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Although the Tambora eruption was the largest eruption in recorded history, it was dwarfed by numerous other prehistoric eruptions. A similar sized, or possibly slightly larger, eruption occurred at Lake Taupo on the North Island in what is now New Zealand in roughly 180 AD [1], although the island was not yet populated, and thus no one to observe it. The date has been determined from Chinese and Roman records of dramatic sunsets and erratic weather[2], and from radiocarbon dating [3].

The largest eruption during the time that mankind has lived on the planet was the supervolcano at Lake Toba on the island of Sumatra roughly 75,000 years ago which produced around 2800 cubic kilometres of material. There is DNA evidence that the number of Homo sapiens alive were reduced to a few tens of thousand at that time, and it has been hypothesised that this was caused by a volcanic winter brought on by the Toba eruption [4]. An eruption of this size occurs somewhere on the planet every few tens of thousands of years.

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Effects

All vegetation on several nearby islands was destroyed. About 10,000 people died immediately from the eruption, with about 82,000 dying from later consequences of the disaster. Worldwide deaths caused by starvation and disease due to climate change are more difficult to quantify. A kingdom on the flanks of Tambora was buried in the ash, apparently, and a few of its ruins have been discovered (and compared to Pompeii). [5]

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The eruption sent so much volcanic ash into the atmosphere that weather patterns around the world were altered, causing the following year to be nicknamed the "Year Without a Summer". Average global temperatures decreased about 0.3 degrees Celsius (0.5 °F), which seems like a small number, but it is enough to cause significant agricultural problems around the globe. Summer frosts ruined crops as far south as Virginia (by some historical accounts, Thomas Jefferson's crops were ruined), and snow fell in August in New England.

Some historians hypothesize that the cooling after the explosion of Mt. Tambora is at least partly responsible for the concurrent large migration of peoples from New England to the region west of the Ohio River.

The crop failures during 1816 also resulted in a dramatic rise in the price of oats, which led to the starvation of many horses and resulting problems with transportation. It has been posited that this was one of the reasons for Karl Drais's invention of the dandy horse, the precursor to the bicycle.

As with most large rhyolitic eruptions, the eruption of Mt. Tambora caused spectacular and unearthly sunsets with vivid streaks of green for several years. This is caused by ash lingering high in the stratosphere where it is not washed away by rain.

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Quotes from 1815 accounts of the eruption

Metric values added where possible

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Explosion

"The concussions produced by its explosions were felt at a distance of a thousand miles (1600 km) all round; and their sound is said to have been heard even at so great a distance as seventeen hundred miles (2700 km). In Java the day was darkened by clouds of ashes, thrown from the mountain to that great distance (300 miles or 500 km), and the houses, streets, and fields, were covered to the depth of several inches with the ashes that fell from the air. So great was the quantity of ashes ejected, that the roofs of houses forty miles (65 km) distant from the volcano were broken in by their weight. The effects of the eruption extended even to the western coasts of Sumatra, where masses of pumice were seen floating on the surface of the sea, several feet in thickness and many miles in extent."

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Pyroclastic flow

"From the crater itself there were seen to ascend 3 fiery pyroclastic columns, which, after soaring to a great height, appeared to unite in a confused manner at their tops. Soon, the whole of the side of the mountain next to the village of Sang'ir seemed like one vast body of liquid fire. The glare was terrific, until towards evening, when it became partly obscured by the vast quantities of dust, ashes, stones, and cinders thrown up from the crater. Between nine and ten o'clock at night the ashes and stones began to fall upon the village of Sang'ir, and all round the neighbourhood of the mountain."

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Atmospheric disturbance

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"The heat triggered a 'dreadful whirlwind', which blew down nearly every house in the village, tossing the roofs and lighter parts high into the air. In the neighbouring sea-port the effects were even more violent, the largest trees having been torn up by the roots and whirled aloft. Before such a furious tempest no living thing could stand. Men, horses, and cattle were whirled into the air like so much chaff, and then dashed violently down on the ground. The sea rose nearly twelve feet above the highest tide-mark, sweeping away houses, trees, everything within its reach. This whirlwind lasted about 19 seconds."

However, Robock 2002 states that, although cooling did occur post the 1815 erruption, climate cooling had already commenced before this time. This can be observed through the ice core records of both Greenland and Antarctica where the sulfuric layers deposited from the eruption have been restored. They show another large layer of such substances due to a large eruption in 1808 which is as yet undefined. Thus, the climate was already experiencing cooling. If the Mount Tambora eruption had occurred when the global climate was warmer, it is highly possible that the effects would have been far less harsh.

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Gradual decrease

"The 'awful internal thunderings of the mountain' continued with scarcely any intermission until the 11th of July, when they became more moderate, the intervals between them gradually increasing until the 15th of July, when they ceased. Almost all the villages for a long distance round the mountain were destroyed. By far the greatest part of this destruction was wrought by the violence of the whirlwind which accompanied the eruption."

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