We forwarded this question to a volcano expert: Lee Siebert, director of the Global Volcanism Program at the Smithsonian Institution in Washington, D.C. Mr. Siebert was kind enough to provide the following information.
The 1815 eruption of Mount Tambora in Indonesia is generally considered to have caused the most eruption-related deaths. In the past, many sources listed the estimated number of fatalities as 92,000, but more recently the number has been revised down to about 60,000.
Roughly 11,000 of these fatalities were caused by pyroclastic flowsmasses of hot gas and rock that raced down the slopesand other direct effects of the eruption. The roughly 49,000 other fatalities occurred in the famine that hit the region in the aftermath of the eruption.
This figure is an estimate for famine-related deaths only in Indonesia. But experts believe that many, many more people around the world died as a result of famines linked to the eruption. The event released such a tremendous amount of volcanic ash into the atmosphere that temperatures around the world were lowered for several years. In fact, 1816 is known as “the year without a summer.” Crop failures occurred in Europe, China, and many other parts of the world in that year, leading to famines. Unfortunately, we do not have reliable estimates of the number of deaths that occurred in these famines.
There are other eruptions for which even larger numbers of famine deaths were reported. However, it is very difficult to determine the extent to which eruptions contribute to famines; often there are other factors that play a part.
For example, the Russian famine of 1601-1603, in which perhaps 2 million people died, has been linked to the eruption of Huaynaputina volcano in Peru in 1600. But global famines due to expanding populations and insufficient food production had begun in the 1590s, and the year 1600 falls within the period known as the Little Ice Age, during which parts of the Northern Hemisphere experienced colder-than-average temperatures. Therefore it is hard to say how much the Huaynaputina eruption was responsible for the famine in Russia.
The 1783 eruption of Asama volcano in Japan is associated with the Great Tenmei Famine in which anywhere from tens of thousands to more than a million people died. The famine had begun in the year before the eruption, but the eruption undoubtedly made it much more severe.
Famines are an indirect result of volcanic eruptions. If we look only at fatalities that are direct results of eruptions, then the 1883 eruption of Krakatau volcano in Indonesia ranks at the top of the list. This explosive eruption resulted in 36,417 fatalities, most from tsunamis.
Two other eruptions rank close behind Krakatau in this category. The eruption of Ilopango volcano in present-Ecuador in the 5th century A.D. caused an estimated 30,000 fatalities in the area swept by pyroclastic flows. About 29,500 people died in the 1902 eruption of Monte Pelee in Martinique; almost all of these fatalities were from pyroclastic flows that swept over St. Pierre and neighboring towns.
(Question submitted by a 7th-grade student at Tantasqua Regional Junior High School in Fiskdale, Massachusetts.)