DESCRIPTION:
Tambora Volcano, Indonesia

Tambora is on Sumbawa Island along the east Sunda Arc. It lies some 300 kilometers behind the Sunda Trench, but the subduction zone in that area has a shallow dip and is less than 200 kilometers deep beneath Tambora (Alzwar and others, 1981). Tambora is a large stratovolcano composed dominantly of nepheline-normative, leucite-bearing trachybasalt and trachyandesite (Petroeschevsky, 1949; Foden and Varne, 1980; Alzwar and others, 1981; Barberi and others, 1983; Self and others, 1984; Foden, 1986). Before its eruption in 1815, Tambora might have been in repose for as much as 5,000 years (Barberi and others, 1983).

At least 6 months and probably about 3 years of increased steaming and small phreatic eruptions preceded the 1815 Tambora eruption, the largest in historical time (Stewart, 1820; Zollinger, 1855; Crawfurd, 1856; Stothers, 1984; Sigurdsson and Carey, 1987). A moderately large explosive eruption occurred on 5 April 1815, from which ash fell in east Java and thunderlike sounds were heard up to 1,400 kilometers away. A still larger eruption occurred on 10-11 April, beginning as "three columns of fire rising to a great height" (Zollinger, 1855, p.19) and ultimately ejecting about 50 cubic kilometers of magma (dense rock equivalent) (Self and others, 1984; Sigurdsson and Carey, 1987). the eruption left a deep summit caldera where previously a much higher stratovolcano had stood. Earthquakes were felt as far away as Surabaya (500 kilometers), possibly reflecting the caldera collapse.

A small, postcaldera cone and lava flow, Doro Afi Toi, originated sometime between 1847 and 1913 (Pannekoek van Rheden, 1918; Neumann van Padang, 1951). A strong earthquake on 13 January 1909, with an epicenter near Tambora (8.5degreesS, 117.4degreesE), was "presumably connected with Tambora" (Koninklijk Magnetisch en Meteorologisch Observatorium te Batavia, 1911). Might the earthquake have occurred during formation of Doro Afi Toi?

The June 1991 eruption of Mount Pinatubo was global. Slightly cooler than usual temperatures recorded worldwide and the brilliant sunsets and sunrises have been attributed to this eruption that sent fine ash and gases high into the stratosphere, forming a large volcanic cloud that drifted around the world. The sulfur dioxide (SO2) in this cloud -- about 22 million tons -- combined with water to form droplets of sulfuric acid, blocking some of the sunlight from reaching the Earth and thereby cooling temperatures in some regions by as much as 0.5 degrees °C. An eruption the size of Mount Pinatubo could affect the weather for a few years.

A similar phenomenon occurred in April of 1815 with the cataclysmic eruption of Tambora Volcano in Indonesia, the most powerful eruption in recorded history. Tambora's volcanic cloud lowered global temperatures by as much as 3 degrees °C. Even a year after the eruption, most of the northern hemisphere experienced sharply cooler temperatures during the summer months. In parts of Europe and in North America, 1816 was known as "the year without a summer."

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