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The 1815 Mount Tambora Eruption – Largest Volcanic Eruption in Recorded History and the Year without a Summer

Aerial view of the caldera of Mt Tambora at the island of Sumbawa, Indonesia

Aerial view of the caldera of Mt Tambora at the island of Sumbawa, Indonesia

The 1815 Mount Tambora eruption was the largest volcanic eruption in recorded history with an approximate VEI-7. This eruption caused serious climatic deviations across the globe including a phenomenon called “Volcanic Winter.”

The year following the eruption, 1816 became the “Year without a Summer” because of the effect this eruption had on the European and North American Weather. As a result of this there was widespread famine. Crops failed across the Northern Hemisphere as there was frost in the month of July and also in a few countries in the tropical regions as the monsoons failed. It also created a three year chain of volcanic events.


Explanation of Terms used:

Stratovolcano – a tall, conical volcano built up of many layers (strata) of hardened lava, tephra, pumice, and volcanic ash

VEI – Volcanic Explosivity Index - measurement used to quantify the amount of ejected material during eruption

Subduction – A geological process in which one edge of a crustal plate is forced sideways and downward into the mantle below another plate

Magma – Molten rock in the earth's crust

Pyroclastic flows – Made up of or containing rock fragments or ash from a volcanic eruption

Hydrous magma – magma containing water (especially water of crystallization as in a hydrate)

Tephra - the solid material thrown into the air by a volcanic eruption that settles on the surrounding areas

Exsolution – the process in which a solution of molten rocks separate into its constituents upon cooling

Caldera – A large crater caused by the violent explosion of a volcano that collapses into a depression

Pacific Ring of Fire – an area where a large number of earthquakes and volcanic eruptions occur in the basin of the Pacific Ocean

Typhus - a bacterial disease spread by lice or fleas and characterized by skin rash and high fever

Archipelago - A group of many islands in a large body of water

Note: Please have a look at the pictures and diagrams to the right, to get a better understanding of the terms used and of what follows.


A brief introduction to Mount Tambora:

  • The Mount Tambora is an active stratovolcano on the island of Sumbawa in Indonesia. It is a part of the Sunda Arc (which is a string of volcanic islands on the Pacific ring of fire). Sunda arc forms part of the southern chain of the Indonesian archipelago. It lies 340 km to the North of the Java Trench system.
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Why and how do volcanoes occur?

  • The island of Sumbawa is surrounded in the north and the south by oceanic crust and the Mount Tambora was formed as a result of an active subduction zone beneath it. This area has been leaking magma into a chamber inside the mountain (magma chamber) thereby raising the mountain as high as 4,300 m making it one of the tallest peaks in the Indonesian archipelago. The convergence rate at this zone is 7.8 cm per year.
  • The elevation of Mount Tambora after the eruption is 2,850 m and the age of the rock is 57,000 years.
  • Before the eruption in 1815, Tambaro had a symmetrical cone shape with one central vent. The diameter of the base is 60 km. Since the eruption in 1815 there have been at least twenty parasitic cones that have been producing basaltic lava.
  • The magma chamber inside the mountain filled over a period of several years and finally erupted violently on the 10th of April 1815.
  • Mount Tambora forms its own peninsula called the Sanggar Peninsula which is an area of research and studies for biologists, archaeologists, seismologists and volcanologists.
Major volcanoes in Indonesia

Major volcanoes in Indonesia

Pre 1815 Mount Tambaro Eruption:

  • This Volcano was dormant for many centuries (around 5,000 years according to geological evidence), and this was due to the cooling of the hydrous magma in the magma chamber.
  • During the cooling and crystallisation process of the magma, at larger depths of around 1.5 to 4.5 km, exsolution was formed. Magma also reacted with ground water, and as a result of this, the volcano released steam, ash and rocks. This led to a high pressure and temperature inside the magma chamber of (about 4,000 to 5,000 bar with a temperature of 700 to 850 degree Celsius).
  • Due to this, the caldera started to rumble and got back into action in 1812, generating dark smoke and clouds, resulting in the eruption in 1815.

The 1815 Mount Tambora Eruption:

  • Mount Tambaro entered a period of high activity in 1812 and the biggest activity was the one in April 1815.
Location of Tambora in the Indonesian Archipelago

Location of Tambora in the Indonesian Archipelago

  • On the evening of the 5th of April 1815, a moderate eruption occurred, shooting a volcanic column of almost 25 km into the sky along with thundery explosive sounds. These sounds were heard as far as Makassar (380 km away), Jakarta (1,260 km away) and Ternate (1,400 km away), lasting for two hours.
  • On the 6th of April, volcanic ash fell in the East of Java with slight explosive sounds and this lasted till the 10th of April.
  • The massive eruption took place on the 10th of April 1815 at around 7 pm when the eruption heightened where three columns of fire rose up (witness statement by Rajah of Sanggar), and the mountain turned into a flowing mass of liquid fire wiping out the villages of Tambora and Sanggar. They travelled up to 20 km from the vent
  • Around 8 pm, pumice stones of around 20 cm in diameter fell down, followed by ash around 9 to 10 pm.

Pyroclastic clouds, the real killers

  • Pyroclastic flows, flowed down (almost 125 miles an hour speed) all the sides of the peninsula into the sea, wiping off the village of Tambora. This continued with loud explosions till the evening of the 11th of April 1815.
  • This was the largest volcanic eruption recorded in history. The VEI-7 eruption had totally ejected a volume of 160 km3 of tephra. This created a caldera of width 6 to 7 km and depth 600 to 700 m.
  • The height of the mountain fell from around 4,300 m before eruption to 2,850 m after the eruption as around 1220 to 1450 m of the top portion (almost a mile tall) of the mountain was reduced to ash and rubble.
  • It was an explosive central vent eruption. There were pyroclastic flows and caldera collapse.
  • The pyroclastic flow uprooted trees and carbonated the houses and people along with livestock along the direction of flow, destroying forests and grasslands.
  • The explosion was heard as far as 2,600 km in the island of Sumatra where it was first thought to be sound of gunfire and heavy volcanic ash fell almost 1,300 km away as far as Borneo, Java, Maluku and Sulawesi islands.
  • A whirl wind also developed in the neighbouring areas destroying houses and trees, and this lasted for more than an hour.
  • Nitrous odour was felt in Batavia and heavy tephra-coloured rain fell that started to retreat between 11 and 17th April 1815.
  • The eruption column reached a height of around 43 km reaching the stratosphere with coarser ash falling 1 or 2 weeks after the eruption and fine ash staying in the atmosphere for months and years at a height of 10 to 30 km.
  • The pyroclastic flows caused tsunamis of various heights (up to 5 m) from 10 pm till midnight in the nearby islands killing 4,600 people and causing huge land and property damage.
  • The volcanic activity lasted till July 1815 when the activity finally stopped.
  • The volcano destroyed all agricultural lands in the region, leading to starvation. The death toll was estimated to be around 71,000 people. Around 11,000 to 12,000 people were killed directly by the eruption and the rest of them died as a result of starvation and diseases that spread after the eruption. Due to high sulphur content and other toxic gases in the atmosphere people became sick with lung diseases.

Casualties due to the 1815 Mount Tambora Eruption:

Different authors / researchers have estimated the total death differently.

  • According to Zollinger in 1855, it is estimated that there were 10,000 deaths due to pyroclastic flows, 38,000 deaths due to starvation, 10,000 deaths due to disease and hunger
  • According to Petroeschevsky’s figures in 1949, 48,000 were killed in Sumbawa and 44,000 were killed in Lombok.
  • According to Stothers figures in 1984, a total of 88,000 people were killed
  • According to Tanguy, who spent many months in Sumbawa after the eruption, he included victims from Bali and East Java who had died of famine and disease and he estimated the direct death as 11,000 and deaths due to famine and diseases as 49,000.
  • According to Oppenheimer’s figures in 2003, he estimated a total of 71,000 deaths.
  • Apart from the above figures around 200,000 people in Eastern and Southern Europe died of typhus and hunger

Aftermath of the 1815 Mount Tambora Eruption:

  • There was pitch darkness as far as 600 km away from the mountain for up to 2 days.
  • Pyroclastic flows spread to around 20 km from the summit and the Indonesian islands were struck with tsunami waves of height around 4 m.
  • All flora in the island were ruined and trees that were uprooted were covered with pumice ash and washed into the sea.
  • Clouds of thick ash covered the summit even till the 23rd of April 1815
  • Explosions ceased on the 15th of July and smoke emissions were observed till 23rd of August.
  • Flames and rumbling aftershocks were witnessed till August 1819.
  • The eruption left a caldera 6 km wide and 1,250 m deep
  • Ships were trapped in harbours due to floating islands of pumice almost a km wide and rafts of pumice even a few years after the eruption.
  • Ash rained down for weeks, fresh water sources were contaminated and houses collapsed under the debris.

Effects of the 1815 Mount Tambora eruption across the globe:

  • Central Greenland had sulphate concentration in its ice-core (studied while researching through the layers of ice, one particular layer having high sulphur concentration for the year 1816).

Note: Layers of ice are similar to annual growth rings on a tree.

Sulfate concentration in ice core from Central Greenland, accurately dated by counting oxygen isotope seasonal variations

Sulfate concentration in ice core from Central Greenland, accurately dated by counting oxygen isotope seasonal variations

  • The eruption released sulphur into the stratosphere that caused a deviation from normality to the global climate and taking into account various methods used to detect the amount of sulphur mass ejected into the stratosphere, it is estimated to be about 10 to 120 million tonnes.
  • Dry fog was observed in the North-eastern parts of United States during the spring and summer of 1815. The fog dimmed and reddened the sunlight so much that the sunspots were visible to the naked eye. This formed a “Stratospheric Sulphate Aerosol Veil” as neither wind nor rain could disperse the fog.

Note: gases react with water vapour in the atmosphere, forming tiny little droplets of sulphuric acid that became suspended in the stratosphere, creating a veil over the Earth and this is called Stratospheric Sulphate Aerosol Veil

  • Countries in the Northern Hemisphere experienced severe weather conditions in the summer of 1816 with the average global temperature dropping down from 0.4 to 0.7 degree Celsius. Most of the solar radiation was reflected back by the ash clouds in the atmosphere. An ice dam formed in Switzerland due to cold temperatures.
  • There was frost and snowfall (ash fell with snow) in many cities in the U.S., Canada and Europe in June 1816 and this was the coldest year for the northern hemisphere after the year 1601 (due to Huaynaputina eruption in Peru in 1600).
  • Parts of Europe experienced stormier winter.
  • Indian monsoons were disrupted causing famine due to failed harvest. This also led to cholera in Bengal.
  • China saw flood in coastal areas, and cold weather killed crops and water buffaloes.
  • Many livestock died in New England between 1816 – 1817.
  • Heavy rain and colder temperatures affected harvest in the UK and Ireland. Families in Wales travelled long distances looking for food. Ireland saw famine due to failure of wheat, oats and potatoes. Typhus broke out in Ireland in the late 1816, killing thousands of people. Also Napoleonic wars during those times made things worse.
  • According to Patrick Webb, a dean at Tufts University's Friedman School of Nutrition Science, people ate rats and fought over the available roots.
  • Europe had an average of 31 inches of rain during the Summer of 1815 and Ireland had nonstop rain for 8 weeks.
  • Food prices rose hugely in Germany also leading to riots, looting and demonstrations in many European countries.

The caldera of Mount Tambora

Follow-up activity of the eruption:

  • There were activities and small eruptions of VEI-2 in August 1819 with flames and rumbling aftershocks.
  • Around 1880 ± 30 years, Tambora had erupted inside the caldera. There were small lava flows and parasitic cones inside the caldera especially the Doro Api Toi (formed between 1847 and 1913).
  • There have been minor activities since then and the last eruption recorded was in 1967 with small eruption but no explosion.

Facts about the 1815 Mount Tambora Eruption:

  • The 1815 Mount Tambora eruption caused a phenomenon called the Volcanic Winter and made the year 1816 known as the Year without a Summer.
  • An excavation by archaeologists in 2004 revealed cultural remains and two adults buried by the eruption 3 m deep
  • The explosive sounds, sounded much like distant guns and hence a unit of troops was marched from Djocjocarta in expectation that a neighbouring post was attacked. Coast boats were dispatched supposedly thinking that a ship was in distress.
  • Lt Philips who was ordered by Sir Stamford Raffles to go to Sumbawa said that he travelled through the western part of the island and saw remains of corpses, deserted villages, fallen houses, survivors moved far in search of food, etc. He also mentioned that severe diarrhoea prevailed due to the drinking waters infused with ashes, and this killed a huge number of people including horses.
  • One of the pumice rafts were found in the Indian Ocean near Calcutta in October 1815.
  • The fine ash was spread across the globe by winds and these created vibrant coloured sunsets and twilights. These were observed in England in June, July, September and October 1815 where the twilight sky was orange or red at the horizon and purple or pink above it.