In April 1815, Mount Tambora, a volcano on the island of Sumbawa in present-day Indonesia (then part of the Dutch East Indies), erupted in what is now considered the most powerful volcanic eruption ever recorded. This eruption had a volcanic explosivity index (VEI) of 7 and released between 37 and 45 cubic kilometers (8.9 to 10.8 cubic miles) of dense-rock equivalent material into the atmosphere. It was the most recent confirmed eruption with a VEI of 7.
Although the eruption reached its strongest point on April 10, 1815, increased steam and small phreatic eruptions continued for the next 6 months to 3 years. Ash from the eruption spread around the world and caused global temperatures to drop, leading to an event known as the Year Without a Summer in 1816. This period of sudden climate change caused extreme weather and failed harvests in many regions globally. Several climate factors worked together in a way that has not been observed after any other major volcanic eruption since the early Stone Age.
Chronology of the eruption
Mount Tambora was not active for many years before 1815. This was because the magma inside its closed chamber gradually cooled over time. Inside the chamber, between 1.5 and 4.5 km (5,000 and 15,000 ft) deep, a high-pressure fluid formed as the magma cooled and solidified. This caused the chamber to become extremely pressurized, reaching about 4,000–5,000 bar (400–500 MPa; 58,000–73,000 psi), with temperatures between 700–850 °C (1,290–1,560 °F). In 1812, the volcano began to make loud noises and produced a dark cloud. On April 5, 1815, a massive eruption happened, with explosion sounds heard as far as Makassar on Sulawesi, 380 km (240 mi) away; Batavia (now Jakarta) on Java, 1,260 km (780 mi) away; and Ternate on the Molucca Islands, 1,400 km (870 mi) away. On April 6, volcanic ash began falling in East Java, with faint explosion sounds lasting until April 10. On April 10, people in Trumon, Sumatra, more than 2,600 km (1,600 mi) away, thought they heard the sound of gunfire. New research suggests the eruption’s sounds were heard even farther, in Nong Khai (modern-day Thailand), 3,352 km (2,061 mi) away; Vientiane (modern-day Laos), 3,368 km (2,072 mi) away; and possibly Mukdahan (Thailand), 3,117 km (1,919 mi) away.
At about 7:00 pm on April 10, the eruptions grew stronger. Three plumes of smoke rose and merged. The entire mountain became a flowing mass of "liquid fire." Pumice stones up to 20 cm (8 in) in size began falling around 8:00 pm, followed by ash between 9:00 pm and 10:00 pm. Soon after, a violent whirlwind hit the village of Saugur (now Sangar), destroying nearly every house and lifting large trees into the air. Pyroclastic flows traveled down the mountain to the sea on all sides of the peninsula, destroying the village of Tambora and covering about 874 km (337 sq mi) of land. A moderate tsunami struck islands in the Indonesian archipelago on April 10, reaching up to 4 m (13 ft) in height in Sanggar around 10:00 pm. Another tsunami, 1–2 m (3–7 ft) high, was reported in Besuki, East Java, before midnight, and one 2 m (7 ft) high in the Molucca Islands. The total number of tsunami-related deaths is estimated to be about 4,600. Loud explosions were heard until the next day, April 11. Volcanic ash spread as far as West Java and South Sulawesi. A strong smell of nitrogen was noticed in Batavia, and heavy rain mixed with volcanic material fell, ending between April 11 and April 17.
The first explosions were heard on the island in the evening of April 5. People in every area noticed the sounds, which continued until the next day. At first, the noise was thought to be distant cannon fire, leading troops to march from Djocjocarta in fear that a nearby post was under attack. Boats were also sent along the coast to search for a ship in distress.
The eruption had an estimated VEI of 7. About 41 km (10 cu mi) of pyroclastic trachyandesite was ejected, weighing around 10 billion tonnes. This created a caldera 6–7 km (3.5–4.5 mi) wide and 600–700 m (2,000–2,300 ft) deep. The density of ash that fell in Makassar was 636 kg/m (39.7 lb/cu ft). Before the eruption, Mount Tambora’s peak was about 4,300 m (14,100 ft) high, making it one of the tallest peaks in the Indonesian archipelago. The eruption reduced its height by about one-third, to 2,851 m (9,354 ft).
The 1815 Tambora eruption is the largest observed eruption in recorded history, as shown in the table below. The explosion was heard at least 2,600 km (1,600 mi) away and possibly over 3,350 km (2,060 mi) away. Ash fell at least 1,300 km (810 mi) away.
Aftermath
During my journey to the western part of the island, I traveled through most of Dompo and a large part of Bima. The extreme suffering of the people there was very difficult to see. Along the road, I saw the remains of several bodies and places where others had been buried. The villages were mostly empty, and many homes had collapsed. The few people who remained had left to find food. After the eruption, a serious illness called diarrhea spread in Bima, Dompo, and Sang'ir, killing many people. Local people believed this illness was caused by drinking water mixed with ash. Many horses also died from the same illness.
All plants on the island were destroyed. Trees, mixed with pumice ash, washed into the sea and formed floating rafts as large as five kilometers across. Between October 1st and 3rd, British ships named Fairlie and James Sibbald saw large pumice rafts about 3,600 kilometers west of Tambora. Thick clouds of ash still covered the mountain’s top on April 23rd. Eruptions stopped on July 15th, but smoke was still seen as late as August 23rd. Activity began again in August 1819 with a small eruption that included "flames" and loud shaking, and it was considered part of the 1815 eruption. This event was recorded as a 2 on the VEI scale.
The eruption sent a column of ash more than 43 kilometers high into the stratosphere. Larger ash pieces fell to the ground within one to two weeks after the eruption, but smaller particles stayed in the air for months or years, reaching heights of 10 to 30 kilometers. Global winds carried these fine particles around the world, creating bright, colorful sunsets and twilights. In London, people saw unusually bright and colorful sunsets and twilights frequently between June 28 and July 2, 1815, and again between September 3 and October 7, 1815. The sky often glowed orange or red near the horizon and purple or pink above.
Estimates of deaths vary by source. Zollinger (1855) said about 10,000 people died directly from the eruption, likely due to fast-moving hot gas and ash flows. On Sumbawa, 18,000 people died from starvation or disease. About 10,000 people on Lombok died from disease and hunger. Petroeschevsky (1949) estimated 48,000 deaths on Sumbawa and 44,000 on Lombok. Stothers (1984) and others agreed with Petroeschevsky’s total of 88,000 deaths. However, Tanguy (1998) and others questioned these numbers, saying they were based on unclear sources. Tanguy used Zollinger’s records from Sumbawa and Thomas Raffles’s notes to revise the estimate to 11,000 deaths from the eruption itself and 49,000 from later famine and disease. Clive Oppenheimer estimated at least 71,000 deaths in total. Reid estimated 100,000 people died from the eruption’s direct and indirect effects on Sumbawa, Bali, and other areas.
Disruption of global temperatures
The eruption caused a volcanic winter. During the Northern Hemisphere summer of 1816, global temperatures dropped by 0.53 °C (0.95 °F). This cooling caused about 90,000 deaths directly or indirectly. The eruption of Mount Tambora was the main reason for this climate change. Other eruptions happened in 1815, but Tambora was a VEI-7 eruption, meaning it released a column of volcanic material 45 km (148,000 ft) tall. This was much larger than other eruptions from that time.
The VEI scale measures the amount of material ejected during an eruption. A VEI-7 eruption releases about 100 km (24 cubic miles) of material. Each step below VEI-7 is ten times smaller. The 1815 eruption happened during the Dalton Minimum, a time when the sun produced less energy than usual. Volcanic activity greatly affects climate, both near and far. Scientists did not fully understand this connection until the 1883 eruption of Krakatoa, which changed the sky color.
The size of a volcanic eruption determines how much it affects climate and chemical processes. Even small eruptions can cause changes in local areas. When volcanoes erupt, they release gases like carbon dioxide (CO₂), water, hydrogen, sulfur dioxide (SO₂), hydrogen chloride, hydrogen fluoride, and others. CO₂ and water are greenhouse gases, which make up 0.0415% and 0.4% of Earth’s atmosphere, respectively. Though these gases are small in amount, they trap heat from the sun and send it back to Earth.
The 1815 eruption sent SO₂ into the stratosphere, causing unusual global weather. Scientists used different methods to estimate how much sulfur was released: petrological analysis, light measurements from observations, and sulfate levels in ice cores from Greenland and Antarctica. These estimates ranged from 10 to 120 million tonnes of sulfur.
In the spring and summer of 1815, a thick "dry fog" appeared in the northeastern United States. The fog made sunlight dim and red, allowing sunspots to be seen with the naked eye. Wind and rain could not remove the fog. Later, scientists identified it as a layer of sulfate particles in the stratosphere. In 1816, the Northern Hemisphere faced extreme weather, called the "Year Without a Summer." Global temperatures dropped by about 0.4 to 0.7 °C (0.7 to 1.3 °F), harming agriculture worldwide.
On June 4, 1816, frost was reported in high areas of New Hampshire, Maine (then part of Massachusetts), Vermont, and northern New York. On June 6, snow fell in Albany, New York, and Dennysville, Maine. On June 8, snow in Cabot, Vermont, was still 46 cm (18 in) deep. These conditions lasted at least three months, destroying crops in North America. Canada also had extreme cold that summer, with 30 cm (12 in) of snow near Quebec City from June 6 to June 10.
The year 1816 was the second-coldest in the Northern Hemisphere since about 1400, and the 1810s were the coldest decade on record. This was due to Tambora’s 1815 eruption and possibly another VEI-6 eruption in late 1808. Summer temperatures in 1816, 1817, and 1818 were −0.51 °C (−0.92 °F), −0.44 °C (−0.79 °F), and −0.29 °C (−0.52 °F), respectively. Parts of Europe had stormier winters.
This climate change worsened typhus outbreaks in southeast Europe and the eastern Mediterranean between 1816 and 1819. It disrupted the Indian monsoons, caused three failed harvests and famine, and helped spread a new cholera strain from Bengal in 1816. Many animals died in New England during the winter of 1816–1817. Cool weather and heavy rain ruined crops in the British Isles. Families in Wales traveled far to find food. Famine was widespread in north and southwest Ireland after wheat, oat, and potato harvests failed. The crisis was worst in Germany, where food prices rose sharply, and protests, riots, fires, and looting occurred in many European cities. This was the worst famine of the 19th century.
Effects of volcanism
Volcanic activity changes the atmosphere in two ways: it causes short-term cooling when sunlight is reflected and long-term warming due to more carbon dioxide in the air. Most water vapor and carbon dioxide are trapped in clouds within weeks or months because both are already in the air in large amounts, so their effects are not very big. Some scientists think a volcanic eruption in 1809 might have helped lower global temperatures.
Impact of the eruption
The eruption of Tambora was much larger than the 1991 eruption of Mount Pinatubo. Scientists estimate that Tambora released about 33 gigatons of energy, which is equal to 1.4 × 10^18 joules. The top of the mountain collapsed by about 1,220 meters (4,000 feet), reducing the mountain’s height by one-third. Around 100 cubic kilometers (24 cubic miles) of rock were thrown into the air. Toxic gases, including sulfur, were released into the atmosphere. Sulfur caused lung infections, and volcanic ash covered areas up to 75 kilometers (45 miles) from the eruption with more than 100 centimeters (40 inches) of ash. Within 500 kilometers (300 miles), ash fell about 5 centimeters (2 inches) thick, and ash was found as far as 1,300 kilometers (810 miles) away. The ash destroyed crops, causing food shortages in Indonesia. Gases like hydrogen chloride made rain extremely acidic, killing crops that survived. Food shortages were worsened by the Napoleonic Wars, floods, and cholera.
Volcanic ash in the atmosphere reflected sunlight for months, making summers unusually cold and worsening food shortages. China, Europe, and North America experienced below-normal temperatures, which harmed harvests. Monsoon patterns in China and India changed, causing floods in the Yangtze Valley and forcing thousands of people to leave coastal areas. Gases in the atmosphere reduced global temperatures by 0.4 to 0.7 degrees Celsius (0.7 to 1.3 degrees Fahrenheit) over a decade. An ice dam formed in Switzerland during 1816 and 1817. In 1816, spring and summer temperatures stayed cool or freezing, while 1817 was extremely cold, with temperatures below −34 degrees Celsius (−30 degrees Fahrenheit) in parts of New York. Freezing temperatures lasted into June in Europe and North America, with snow up to 32 centimeters (13 inches) deep in August, killing crops. In 1816, growing seasons in Massachusetts and New Hampshire lasted less than 80 days, leading to failed harvests. Unique sunsets and red fog were seen in Europe and the eastern U.S., and these conditions lasted for about 2.5 years.
Scientists studied ice cores from 1810 to 1819 to learn about atmospheric gases. Sulfur levels in ice from Antarctica and Greenland dropped from 5.0 in January 1816 to 1.1 in August 1818. This suggests that 25–30 megatons of sulfur were released into the atmosphere, mostly from Tambora. Sulfur levels in ice cores changed the most in 5,000 years. Scientists estimate sulfur amounts from 10 to 120 megatons, with an average of 25–30 megatons. High sulfur levels may have warmed the upper atmosphere by about 15 degrees Celsius (27 degrees Fahrenheit) for four years, delaying cooling that lasted nine years.
Climate data show that smaller differences between daily high and low temperatures may have contributed to lower average temperatures. Nights were warmer due to clouds, and days were cooler as clouds cleared. Cloud patterns changed nightly, similar to fog. Before 1810, temperature differences were about 7.9 degrees Celsius (14.2 degrees Fahrenheit). During 1815–1817, differences were only about 2.3 degrees Celsius (4.1 degrees Fahrenheit). This made temperature patterns in 1816 more steady and 1817 colder overall. Europe’s coolest areas were in southeastern England, northern France, and the Netherlands, while North America’s coolest areas were in New York, New Hampshire, Delaware, and Rhode Island. Rainfall in 1816 was 80% higher than normal, with heavy snow in Switzerland, France, Germany, and Poland. In contrast, 1818 had unusually low rainfall, causing droughts in Europe and Asia. Russia had warm, dry summers from 1815 to 1817. Ocean temperatures near the Baltic Sea, North Sea, and Mediterranean Sea dropped, possibly showing changes in ocean currents and wind patterns.
Considering the Dalton Minimum and earlier droughts and famines, the Tambora eruption made extreme climate conditions in 1815 worse. Other eruptions and climate events would have caused about 0.2 degrees Celsius (0.4 degrees Fahrenheit) of global cooling, but Tambora increased this effect significantly.