Tambora eruption - April 1815, Indonesia

Following several centuries of repose, small ash clouds were observed at Tambora on Sumbawa island in 1812. On 5 April 1815, the first serious eruption began, lasting for 2 hours. A second major explosion on 10 April lasted for approximately 3 hours with a discharge rate estimated at 3 × 108 kg s-1. Collapse of the eruption column generated pyroclastic flows that destroyed the villages of Tambora and Sanggar. Over the next three or four days 50 km³ of magma was expelled in the form of ash fall and pumice-rich Pyroclastic flows, making the eruption probably the largest of the past 1,000 years. Large explosions continued until the 11 April with moderate blasts continuing until the 15 April 1815¹.

The explosions from the volcano could be heard as far away as Mukomuko (200 km) and even in Trumon in Sumatra (2600 km). In the eastern districts of Java the eruptions were violent enough to shake houses. Ash-fall blocked out sunlight for many days across the entire island of Sumbawa. Although south-easterly monsoon winds blew much of the ash west of Tambora, in Baryuwangi in eastern Java ash fall still accumulated to a depth of 23 cm¹.

The cone of Tambora before the eruption was estimated to be as high as 4300 m, which the eruption reduced to 2,850 m, as well as opening a summit caldera 6 km wide and 1 km deep¹.

The VEI (Volcanic Explosivity Index) 7 eruption also produced a devastating tsunami¹,². On the island of Sumbawa, it is estimated that 10,000 people were killed by pyroclastic flows, 32,000 by starvation and another 10,000 due to disease and hunger³. The tsunami also claimed many lives.

The 1815 Tambora eruption was probably the largest eruption in historic time, expelling around 140 gigatonnes of magma and generating an ash cloud that reached a height of up to 43 km. More than 95 percent of the ejected mass was erupted as pyroclastic flows, with 40 percent of this ending up as ash fallout. Floating pumice rafts and charred tree trunks hindered shipping in the area for three years after the eruption¹.

The eruption also produced at least 1011 kg of SO4, leading to a fall in global average temperatures of 0.4 to 0.7ºC⁴ and the so-called ‘Year without a Summer’ in 1816. The effects included extremely cold weather in Europe, the north-eastern USA and the maritime provinces of Canada, leading to crop failures and famine, and the last great subsistence crisis in the western world. Temperatures in western and central Europe were 1-2 º C cooler than the average for the period 1810-1819. Rainfall was also unusually high across much of Europe during the summer of 1815¹.

¹ Oppenheimer, C. 2003. Climatic, environmental and human consequences of the largest known historic eruption: Tambora volcano (Indonesia) 1815. Progress in Physical Geography. Vol. 27, pp 230-259

² Ritchie. D & Gates, A.G. 2001. Encyclopaedia of Earthquakes and Volcanoes. Checkmark Books, New York.

³ Wikipedia. 2007. Mount Tambora
http://en.wikipedia.org/wiki/Mount_Tambora

⁴ Vallelonga, P, Candelone, J.P, Van de Velde, K, Curran, M.A.J, Morgan, V.I & Rosman, K.J.R. 2003. Lead, Ba and Bi in Antarctic Law Dome ice corresponding to the 1815 AD Tambora eruption: an assessment of emission sources using Pb isotopes. Earth and Planetary Science Letters. Vol. 211, pp 329-341