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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 in recorded human history.

This eruption, with a volcanic explosivity index (VEI) of 7, ejected 37–45 km3 (8.9–10.8 cubic miles) of dense-rock equivalent (DRE) material into the atmosphere, and was the most recent confirmed VEI-7 eruption. Although the Mount Tambora eruption reached a violent climax on 10 April 1815, increased steaming and small phreatic eruptions occurred during the next six months to three years. The ash from the eruption column dispersed around the world and lowered global temperatures in an event sometimes known as the Year Without a Summer in 1816. This brief period of significant climate change triggered extreme weather and harvest failures in many areas around the world. Several climate forcings coincided and interacted in a systematic manner that has not been observed after any other large volcanic eruption since the early Stone Age.

Mount Tambora experienced several centuries of dormancy before 1815, caused by the gradual cooling of hydrous magma in its closed magma chamber. An over-pressurization of the chamber of about 4,000–5,000 bar (400–500 MPa; 58,000–73,000 psi) was generated, with the temperature ranging from 700–850 °C (1,290–1,560 °F). On 5 April 1815, a giant eruption occurred, followed by thunderous detonation sounds heard in 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 the morning of 6 April, volcanic ash began to fall in East Java with faint detonation sounds lasting until 10 April. The 1815 Tambora eruption is the largest observed eruption in recorded history, as shown in the table below.

Activity resumed in August 1819—a small eruption with "flames" and rumbling aftershocks, and was considered to be part of the 1815 eruption. Prolonged and brilliantly colored sunsets and twilights were seen frequently in London between 28 June and 2 July 1815, and 3 September and 7 October 1815. Reid has estimated that 100,000 people on Sumbawa, Bali and other locations died from the direct and indirect effects of the eruption.

The eruption of Mount Tambora was the largest cause of this climate anomaly. While there were other eruptions in 1815, Tambora is classified as a VEI-7 eruption with a column 45 km (148,000 ft) tall, eclipsing all others by at least one order of magnitude. Furthermore, the 1815 eruption occurred during a Dalton Minimum, a period of unusually low solar radiation.

The 1815 eruption released SO2 into the stratosphere, causing a global climate anomaly. That was the consequence of Tambora's 1815 eruption and possibly another VEI-6 eruption in late 1808.

It has been suggested that a volcanic eruption in 1809 may also have contributed to a reduction in global temperatures.

By most calculations, the eruption of Tambora was at least a full order of magnitude (10 times) larger than that of Mount Pinatubo in 1991. Volcanic ash was over 100 cm (40 in) deep within 75 km (45 mi) of the eruption, while areas within a 500 km (300 mi) radius saw a 5 cm (2 in) ash fall, and ash could be found as far away as 1,300 km (810 mi). The ash in the atmosphere for several months after the eruption reflected significant amounts of solar radiation, causing unseasonably cool summers that contributed to food shortages. Tambora caused the largest shift in sulfur concentrations in ice cores for the past 5,000 years. Taking into account the Dalton Minimum and the presence of famine and droughts predating the eruption, the Tambora eruption accelerated or exacerbated the extreme climate conditions of 1815.

Quick Facts

• Although the Mount Tambora eruption reached a violent climax on 10 April 1815, increased steaming and small phreatic eruptions occurred during the next six months to three years.
• Mount Tambora experienced several centuries of dormancy before 1815, caused by the gradual cooling of hydrous magma in its closed magma chamber.
• This eruption, with a volcanic explosivity index (VEI) of 7, ejected 37–45 km3 (8.9–10.8 cubic miles) of dense-rock equivalent (DRE) material into the atmosphere, and was the most recent confirmed VEI-7 eruption.
• The 1815 Tambora eruption is the largest observed eruption in recorded history, as shown in the table below.
• The ash from the eruption column dispersed around the world and lowered global temperatures in an event sometimes known as the Year Without a Summer in 1816.

Source material: Wikipedia - "1815 eruption of Mount Tambora". Adapted and summarized for DiscoverScroll. Original contributors are credited through the linked Wikipedia article. Read original on Wikipedia. CC BY-SA 4.0. Changes were made from the original.