Mount Tambora Eruption (1815): The Largest Blast in History

The eruption of Mount Tambora on the island of Sumbawa in April 1815 was the largest volcanic eruption in recorded history. It blew away the top of the mountain, buried two small kingdoms, and killed tens of thousands of people through blast, famine and disease. Its sulphur cloud spread around the globe and cooled the climate, leading to crop failures across the Northern Hemisphere in 1816.

Background: Sumbawa in 1815

Sumbawa lies in the Lesser Sunda Islands, east of Bali and Lombok, in what is now Indonesia. In 1815 it was divided among several small Muslim sultanates and rajadoms, including Bima, Dompu, Sumbawa, Sanggar, Pekat and Tambora. The island was known for horses, honey, sappanwood (used for red dye) and rice, which it traded across the archipelago.

The wider region was then under unusual rule. During the Napoleonic Wars Britain had seized Java and the Dutch possessions in 1811, and Thomas Stamford Raffles governed them as Lieutenant-Governor until the territories were returned to the Netherlands in 1816. Much of what is known about the eruption comes from reports Raffles collected from officials across the islands. He asked residents and officers in Java and the outer islands to send in descriptions of what they had seen and heard, and he published a summary in his History of Java in 1817. These reports, together with accounts from ships’ crews who encountered thick ash and floating rafts of pumice in the seas around Sumbawa, are the main eyewitness sources for the disaster.

Tambora itself was a large stratovolcano, a steep cone built from layers of lava and ash. It had been quiet for centuries and was thought to stand about 4,300 metres high, which would have made it one of the tallest peaks in the East Indies. Rumblings and small explosions were reported from 1812 onward, but nobody understood the warning.

The eruption

On the evening of 5 April 1815 a major explosive phase began. The detonations were heard as far as Java, more than 1,200 kilometres away. In Batavia (now Jakarta) and other towns, officials thought they were hearing cannon fire, and troops and boats were sent out in search of a battle or a ship in distress.

After a lull, the climactic eruption began on the evening of 10 April. According to the Rajah of Sanggar, who survived and later described it to a British officer, three columns of fire rose from the summit and merged into one. Stones and ash rained down, a violent whirlwind tore up trees and houses, and glowing avalanches of hot gas, ash and rock, known as pyroclastic flows, poured down the slopes to the sea.

The explosions were heard on Sumatra, more than 2,000 kilometres away. Ash fell over a vast area, and on Sumbawa, Lombok, Bali and eastern Java day turned to night. Darkness lasted for up to three days in places hundreds of kilometres from the volcano. Pyroclastic flows entering the sea generated tsunamis that struck nearby coasts. The main eruption ended within days, though ash fall and smaller explosions continued until around 15 April.

A mountain blown apart

When the eruption ended, Tambora had lost roughly 1,400 metres of its height. In place of the summit was a caldera, a great collapsed crater about 6 kilometres across and over 1,000 metres deep. The mountain’s peak today stands at about 2,850 metres.

Volcanologists rate the eruption 7 on the Volcanic Explosivity Index (VEI), a scale from 0 to 8. Estimates suggest it ejected roughly 150 cubic kilometres of ash and pumice, equivalent to around 30 to 50 cubic kilometres of dense magma. That is about ten times the output of the Krakatoa eruption of 1883, which is far better known in Europe because it happened in the age of the telegraph.

Human cost

The kingdoms of Tambora and Pekat were destroyed almost completely. Pyroclastic flows and heavy ash fall killed most of their people, and the Tambora language, which was unrelated to its neighbours, disappeared. It is known today only from a short word list collected by officials soon afterwards.

The greater toll came later. Thick ash smothered fields, poisoned water, killed livestock and ruined the rice crop on Sumbawa and neighbouring Lombok. Famine and disease, including diarrhoeal illness, followed. Ash fall also damaged crops on Bali and in eastern Java, where food prices rose sharply in the months that followed. Fresh water was scarce because wells and streams were choked with ash, and many of the deaths were caused by drinking contaminated water. Many survivors fled to other islands, and there are reports of people selling themselves into servitude simply to obtain food.

Raffles sent Lieutenant Owen Phillips to Sumbawa with rice for relief, and Phillips reported scenes of starvation and devastation. In the 1840s the Swiss botanist Heinrich Zollinger visited the island and gathered information that later writers used to estimate the dead, although his own figures are now thought to be too high.

Modern estimates, notably by the volcanologist Clive Oppenheimer, suggest around 10,000 to 12,000 direct deaths and about 71,000 deaths in total on Sumbawa and Lombok. Figures in the literature range from about 60,000 to over 90,000. Whatever the exact number, it remains the deadliest volcanic eruption on record.

Global climate effects

Tambora’s eruption column carried large amounts of sulphur dioxide high into the stratosphere, perhaps 50 to 60 million tonnes. There the gas formed tiny droplets of sulphuric acid, a sulphate aerosol veil that spread around the world and reflected part of the sunlight. Ice cores from both Greenland and Antarctica record a strong sulphate spike from the eruption.

Average global temperatures fell by around 0.4 to 0.7 degrees Celsius over the following year, with much larger local swings. The Northern Hemisphere summer of 1816 was disastrously cold and wet in western Europe and northeastern North America, causing failed harvests and food crises. That year is remembered as the Year Without a Summer.

Brilliant, unusually coloured sunsets were reported in Europe for several years, and some art historians and scientists have linked the vivid skies in paintings of the period to volcanic aerosols. No one at the time connected the cold weather to an eruption on the other side of the world. The link was proposed only in the 20th century, and confirmed by ice-core and tree-ring studies.

Some historians have also suggested that disruption of the Indian monsoon in 1816 and 1817 may have contributed to the emergence of the first cholera pandemic in Bengal. That idea is debated and cannot be proven.

Rediscovering the lost kingdom

For many years Tambora was a footnote in European histories. That changed in the late 20th century as climate scientists traced the 1816 crisis back to Sumbawa.

In 2004 a team led by the volcanologist Haraldur Sigurdsson of the University of Rhode Island, working with the Indonesian Volcanological Survey, excavated a site in a gully on Tambora’s slopes. Under about three metres of volcanic deposits they found the remains of a house, pottery, bronze bowls, iron tools and the remains of people who died in 1815. The press quickly called it the “Pompeii of the East”. Because the people had been buried so quickly, their homes and belongings were preserved in place, as at the Roman town destroyed by Vesuvius in AD 79.

The finds suggested a prosperous community with trade links across the region, confirming accounts that the Tambora kingdom had been relatively well off before it vanished.

Myths and facts

It is often said that Tambora was the largest eruption ever. It is the largest in recorded history, but geological evidence shows that prehistoric eruptions were bigger. The Toba super-eruption in Sumatra about 74,000 years ago was many times larger.

Another common belief is that Krakatoa was the deadlier and more powerful event. Krakatoa killed around 36,000 people, mostly through tsunamis, and its explosion was heard over enormous distances. But Tambora ejected far more material, had a larger effect on climate and caused more deaths.

By the numbers

Timeline

• 1812: Rumblings and small eruptions are reported from Tambora.
• 1815, 5 April: A major explosive phase begins; blasts are heard in Java and mistaken for gunfire.
• 1815, 10 April: The climactic eruption begins in the evening, with pyroclastic flows and tsunamis.
• 1815, 11 April: Explosions are heard on Sumatra; darkness covers much of the region.
• 1815, c. 15 April: The main eruptive activity ends; ash continues to settle.
• 1815, weeks after the eruption: Lieutenant Owen Phillips brings rice relief and reports famine on Sumbawa.
• 1816: Northern Hemisphere crops fail during the Year Without a Summer.
• 2004: Excavations on Tambora’s slopes uncover a village buried in 1815.
• 2015: The eruption’s bicentenary is marked and Mount Tambora National Park is established.

Why it matters

Tambora shows how a single eruption in one part of the world can affect people everywhere. It destroyed whole communities on Sumbawa, caused famine across the region, and cooled the planet enough to bring hunger to Europe and North America. Today it is a key case study for volcanologists and climate scientists preparing for the next great eruption.