Mount Tambora is an active stratovolcano on the island of Sumbawa, Indonesia. Sumbawa is flanked both to the north and south by oceanic crust, and Tambora was formed by the active subduction zone beneath it. This raised Mount Tambora as high as 4,300 m (14,100 ft), making it, in the 18th century, one of the tallest peaks in the Indonesian archipelago.
After a large magma chamber inside the mountain filled over the course of several decades, volcanic activity reached a historic climax in the eruption of 10 April 1815. This eruption was approximately VEI-7, the only eruption unambiguously confirmed of that size since the Lake Taupo eruption in about 180 CE.
With an estimated ejecta volume of 160 km3, Tambora’s 1815 outburst was the largest volcanic eruption in recorded history. The explosion was heard on Sumatra island more than 2,000 km (1,200 mi) away. Heavy volcanic ash falls were observed as far away as Borneo, Sulawesi, Java and Maluku islands. Most deaths from the eruption were from starvation and disease, as the eruptive fallout ruined agricultural productivity in the local region.
The death toll was at least 71,000 people, of whom 11,000–12,000 were killed directly by the eruption; the often-cited figure of 92,000 people killed is believed to be overestimated.
The eruption caused global climate anomalies that included the phenomenon known as “volcanic winter”: 1816 became known as the “Year Without a Summer” because of the effect on North American and European weather. Crops failed and livestock died in much of the Northern Hemisphere, resulting in the worst famine of the 19th century.