1816 - THE YEAR WITHOUT A SUMMER

An Overview of the Eruption of Mount Tamboraby Simon Wickens

Tambora from the Space Shuttle. Image courtesy NASA.

INTRODUCTION

The period 1812 - 1817 was one of unusually intense volcanic activity. This activity reached its peak in April 1815, when Mount Tambora (sometimes spelt Tamboro) on the island of Sumbawa, Indonesia, erupted in one of the most explosive volcanic events of the last 10,000 years. Although this eruption was much bigger than the 1883 Krakatoa event, it was less well-documented. Estimates of the size of the eruption vary, although Christopherson (p 105) quotes one such estimate that 150 cubic km of material was released. To put this into pespective, this would be 25 times the volume of material released by the 1980 Mount St. Helens eruption.

The volcanic activity of the period 1812 - 1817 is believed to have caused a temporary cooling in global temperatures around this time, and the Tambora eruption is thought to be the key to the 1816 climax of the cooling period, the year without a summer. The adverse weather in 1816 had profound effects on North America, Asia and particularly Europe. This site is dedicated to explaining the Tambora eruption, and examining its effects around the world.

Location of Sumbawa, Indonesia.

Original image courtesy of University of Texas library

WHERE DO VOLCANOES OCCUR?

Most volcanic activity (and earthquake activity) is located along linear belts that correspond to tectonic plate boundaries. The USGS website gives a good explanaton of tectonic plate theory. The map below shows global volcano activity distribution. The USGS website also has a good overview of tectonic plate related volcanism. Some volcanic activity takes place in "hot spots" (such as Hawaii) that are not located at tectonic plate boundaries, and the USGS website has a good explanation of the Hawaiian hot spot. As can be seen from the map below, Tambora is located in an area of intense volcanic activity.

Global Volcanic Activity

Original image courtesy The Global Volcanism Program.

Here the Indian-Australian tectonic plate is being subducted beneath the Eurasian tectonic plate at a convergent plate boundary. This boundary is part of the "ring of fire" (which also sees some intense earthquake activity) as shown below. More than half the world's active volcanoes above sea level are located within the ring of fire. The Indonesian chain of volcanoes stretching east from Java can be seen in this spectacular NASA shot at Indonesiaphoto.com.

The Ring of Fire

THE TAMBORA ERUPTION

Diagram of Composite Volcano. Courtesy University of Conneticut.

There are various types of volcano, each of which has its own appearance, location and eruption characteristics (although the differences are often blurred in real life examples). The main volcano types are shield volcanoes (eg the Hawaiian volcanoes), volcanic domes (eg Novarupta, AK), cinder cones (eg Sunset Crater) and composite volcanoes (eg Mt Fuji). Tambora is an example of a composite volcano (these are sometimes called stratovolcanoes). An excellent explanation of the other volcano types can be found at the USGS web site. Composite volcanoes earn their name because they are composed of alternating layers of differing materials following the eruption of lavas and pyroclastics at different times. This alternating eruption pattern and its subsequent deposition pattern allows composite volcanoes form to steep-sided, conical structures that are much larger than cinder cones or volcanic domes. Composite volcanoes often have relatively stiff, sticky andesitic lava (which, compared to other lavas is relatively high in silica content and relatively low in iron and magnesium) that sometimes flows, and sometimes traps enough gases to generate the potential for massive explosions. As magma rises and cools

in a composite volcano it can form a plug that traps gasses in passageways, fissures, cracks and chambers within the volcano, as well as within the magma itself. Over time, the pressure of the trapped and compressed gasses rises to a level that the volcano is not strong enough to contain. The volcano then erupts explosively. Although composite volcanoes produce less lava than shield volcanoes, they produce much more tephra, which includes volcanic ash and dust, cinders, lapilli, scoria, pumice and pyroclastics (fire fragments). The force of the explosion(s) can be enough to lift the ejected debris very high into the atmosphere.

The Tambora eruption is estimated to have rated 7 (or super-colossal) on the volcanic explosivity index (VEI), which runs from 0 to 8. By comparison, the 1981 Mt St. Helens eruption rated 5, and the Krakatoa eruption rated 6. Montgomery (p 110) quotes an estimate that the Krakatoa explosion was the equivalent of 100 million tons of dynamite. The Tambora eruption did not occur as a single event, but rather as a series of events which climaxed between April 10 and April 15. Most accounts give April 12 as the day the mountain blew its top off. The Tombora eruption was comfortably the largest explosion in reliably recorded history. It also threw more debris into the atmosphere than any other eruption in history. Tambora put 25 times more debris into the atmosphere than the 1980 Mount St. Helens eruption, and about 5 times as much as the 1991 Mount Pinatubo eruption. The eruption column reached a height of 28 miles. It was the debris that caused the climatic effects detailed below. The diagram below shows the relative volumes of ejecta produced by Tanbora compared to some other eruptions.

Comparative Ejecta Volumes For Some Historic Eruptions

Image courtesy NASA Classroom of the Future.

EFFECTS ON THE IMMEDIATE AREA

Before Mount Tambora erupted, it is estimated to have been about 4,000m high. The eruption reduced it to 2851m, and left behind a caldera 7 km across. We must rely on contemporary reporting to chronicle most of the effects of the explosion. A good account of these reports can be found at the Nationmaster Encyclopedia. I have summarized the effects below. The concussions produced by the explosions are said to have been felt for 1,000 miles all around, and the sound was reported to be heard 1,700 miles distant from the volcano. In European settlements 200 and 750 miles away the sounds of the eruption were thought to be cannon fire, and ships and soldiers were despatched to investigate what were assumed o be attacks on nearby outposts. In Java, some 300 miles west the day was darkened by the ash, which fell several inches deep. Closer to ground zero, the rooves of houses 40 miles from the eruption collapsed under the weight of ash. All vegetation on several nearby islands died, significant masses of pumice were reported in the ocean off the western coasts of Sumatra, and the immediate area death toll was around 92,000. 10,000 died from the direct effect of the explosion, lava flows, falling debris and pyroclastic flows, with another 82,000 dying subsequently through starvation and disease. The eruption generated an hour long and extremely destructive "whirlwind", and the sea rose 12 feet above its high tide mark, causing widespread flood damage. It was 5 years before new vegetative growth returned to the area within 250 miles from the eruption. Indonesiaphoto.com has a very cool NASA false color image of the Tambora caldera which is a little too large to handle comfortably on this site.

CLIMATIC EFFECTS OF LARGE VOLCANIC ERUPTIONS

Large, explosive volvanic eruptions can punch huge amounts of gasses and dust high into the atmosphere. The gasses have a long term effect on atmospheric composition (and subsequent climate variations). The NOAA Paleoclimatology Data Project has excellent information on this and other mechanisms that have long term effects on the climate. However, volcanic dust is another story in the short term. Volcanic dust takes months to circulate the globe in the upper atmosphere, and years to settle out. While the dust is in the upper atmosphere it can have a profound effect on the short term global climate. The dust takes some months to circle the globe, and while it is in the upper atmosphere it is postulated that it filters out or blocks a portion of the incoming solar radiation. This in turn lowers the temperatures in the lower atmosphere (including that prevailing at the surface). Meanwhile, a temporary spike in sulfur rich gasses combines with water vapour to form more sulfuric acid droplets in the upper atmosphere. These droplets both absorb solar radiation, and scatter it back to space. Recently, better understanding of these processes, allied to better instrumentation, has meant that some direct correlations have been made between major explosive volcanic events and subsequent short term climatic "blips". To use a recent and well studied example, the 1991 eruption of Mt. Pinatubo is thought to have been responsible for a global temperature lowering of 0.5 deg C the

following year (Tarbuk & Lutgens p 104). The delay in measureable effect is explained by the time it takes for such gasses and dust to spread around the globe. 0.5 deg C might not seem much, but in marginal agricultural environments it is enough to delay the arrival of spring thaws, enough to project killing frosts into the growing season, and enough to shorten the growing window. Below you can see this process unfolding in the (relatively minor) 1994 Rabaul Caldera event. 1991 Pinatubo was a pussy cat compared to 1815 Tambora, so what happened to the climate after Tambora?

Eruption Cloud from the 1994 Rabaul Caldera, Papua New Guinea.

Image taken from the space shuttle, and courtesy USGS.

NORTH AMERICA 1816

North America has immortalised 1816 as the year without a summer. Late cold temperatures devastated crops and created a humanitarian disaster. 1816 May through September in Canada saw a series of cold events that killed crops and led to near famine conditions. More than 2 feet of snow blanketed the ground for 4 days in June in Quebec City, and it snowed in June in Montreal. Sub-zero June temperatures damaged crops, and the already shortened growing season was brought to a premature end by hard frosts in mid-September. Meanwhile, in the US, New England experienced snow in June and damaging frosts in July. On 22 August a hard frost reached from New England all the way south to North Carolina. Droughts further complicated matters, and as in Canada, there were killing frosts in September. The severe weather led to widespread crop failure and starvation. In Connecticut and New York State frosts after April are rare, but in 1816 frosts were recorded in every month of the year. July ushered in a notable lack of warm nights and a drought, which in turn ruined the corn harvest in many parts of New England. Prices for corn, grain and oats shot up, and many farmers were ruined by crop failure.

Exactly how much colder the 1816 summer was than usual is difficult to say, and sources differ. The picture is complicated by (compared to modern standards) patchy record keeping. It is also true that New England and Canada did see some warm, summer-like

weather during the summer of 1816. There was even a heat wave in late June. Furthermore, isolated summer cold spells were already well recorded in New England, and they have been repeated since. However, in 1816 these cold snaps were repetitive rather than isolated, they appear to have been relatively harsh, and they were unfortunately timed. In summary, the growing season started late, finished early, was punctuated by unseasonal frosts, featured reduced precipitation and unseasonal precipitation types (eg June snow), and was generally colder than usual. Given these circumstances and their historical (technological) context, it is hardly surprising that much of Canadian and New England agriculture collapsed in 1816. Many historians credit the 1816 failed harvest with the subsequent pulse of American migration to the south and west, which in turn altered the distribution of American agriculture.

EUROPE 1816

The historical record shows us much more climate-induced devastation in Europe in 1816 than in North America. However, this disparity may reflect better record keeping, superior measurement techniques and practices, and higher population densities. It is certainly true that Europe documented a far more severe set of adverse climatic conditions and consequences than did North America. In Ireland, between May and September it rained on 142 out of 153 days. In England the Central England Temperature Series value for the summer of 1816 is 13.37 deg C, to date the 3rd coldest since records began (in 1659); the 2 colder values (1725 and 1695) are from the predating little ice age period. Near Iceland, sea ice persisted into June. Crops failed in southwestern England, France, Germany and Switzerland. Food riots occured in Britain and France, and civil unrest became so bad in Switzerland that a national emergency was declared, and incoming grain purchases from Russia were intercepted at the border and confiscated by hungry citizens. Throughout Europe the price of both rye and wheat soared. In 1816 a typhus epidemic kicked off in southeast Europe and the Mediterranean that would ultimately kill at least tens of thousands (some put the figure in the hundred thousands). Either way, it is certainly true that Tambora reached out around the globe to create massive casualities far beyond its immediate area.

ASIAN EFFECTS

Tambora's effects on Asia are less well documented than its effects in Europe or North America. However, the Asian summer monsoon of 1816 concentrated unusually heavy rains in the far east and Korea, while the Indian monsoon saw very heavy rains concentrated in south India. 1816 also saw the outbreak of a huge cholera epidemic in south India, and the unusual weather is likely to have been at least a contributory factor in the epidemic. There is also evidence of crop failures in Japan and the Yangtze Valley area in China at the same time.

RELATED LINKS

The following are some of the better sites I stumbled across while researching this site:

The Volcano World.

San Diego State University.

The USGS Cascades Volcano Observatory.

Michigan Technological University.

The USGS.

The USGS Alaska Volcano Observatory.

Volcanoes of the world. Some very cool photography here.

The USGS Hawaiian Volcano Observatory.

REFERENCES

Christopherson, R W. Elemental Geosystems 3rd Edition. Prentice Hall, New Jersey, 2001.

Montgomery, C W. Environmental Geology 6th Edition. McGraw Hill, New York, 2003.

Tarbuck, E J & Lutgens, F K. Earth 5th Edition. Prentice Hall, New Jersey, 1996.

This site was created by Simon Wickens as a project for a GLG 110 (Environmental Geology) class undertaken at Pima Community College in the Spring 2004 semester. It was last updated on 05/14/04.