- Volcanic winter
A volcanic winter is the reduction in temperature caused by
volcanic ash and droplets ofsulfuric acid obscuring thesun and lowering thealbedo (increasing the Earth's reflectivity), during a large particularly explosive type of volcanic eruption. Long term cooling effects are primarily dependent upon injection ofsulfide compounds inaerosol forms into the upper atmosphere—thestratosphere — the highest least active levels of the lower atmosphere where little precipitation occurs requiring a lengthy time to wash the aerosols out of the region.Recent cases of volcanic winter
The scales of recent winters are more modest but their effects can be significant. A paper written by
Benjamin Franklin in 1783 blamed the unusually cool summer of 1783 on volcanic dust coming fromIceland , where the eruption ofLaki volcano had released enormous amounts ofsulfur dioxide , resulting in the death of much of the island'slivestock and a catastrophicfamine which killed a quarter of the population. Temperatures in thenorthern hemisphere dropped by about 1 °C in the year following the Laki eruption.The
extreme weather events of 535-536 are most likely linked to a volcanic eruption.In
1452 or1453 , a cataclysmic eruption of thesubmarine volcano Kuwae caused worldwide disruptions.In
1600 , theHuaynaputina inPeru erupted. Tree ring studies show that 1601 was cold.Russia had its worst famine in 1601 to 1603. From 1600 to 1602,Switzerland ,Latvia andEstonia had exceptionally cold winters. The wine harvest was late in 1601 inFrance , and in Peru andGermany wine production collapsed. Peach trees bloomed late inChina , andLake Suwa inJapan froze early [http://www.sciencedaily.com/releases/2008/04/080423135236.htm University of California - Davis (2008, April 25). Volcanic Eruption Of 1600 Caused Global Disruption. ScienceDaily. Retrieved April 25, 2008] .The 1815 eruption of
Mount Tambora , astratovolcano inIndonesia , occasioned mid-summer frosts inNew York State and June snowfalls inNew England in what came to be known as the "Year Without a Summer " of 1816.In 1883, the
explosion ofKrakatoa (Krakatau) also created volcanic winter-like conditions. The next four years after the explosion were unusually cold, and the winter of 1888 was the first time snow fell in the area. Record snowfalls were recorded worldwide.Most recently, the 1991 explosion of
Mount Pinatubo , another stratovolcano in thePhilippines , cooled global temperatures for about 2–3 years. [ [cite journal|author=Brohan, P., J.J. Kennedy, I. Haris, S.F.B. Tett and P.D. Jones|year=2006|title=Uncertainty estimates in regional and global observed temperature changes: a new dataset from 1850|journal=J. Geophysical Research|volume=111|pages=D12106|doi=10.1029/2005JD006548] ]Ancient case of volcanic winters
One proposed volcanic winter happened around 71,000–73,000 years ago following the supereruption of
Lake Toba onSumatra island inIndonesia . In the following 6 years there was the highest amount of volcanic sulphur deposited in the last 110,000 years, possibly causing significantdeforestation inSoutheast Asia and the cooling of globaltemperature s by 1 °C. [ C. Oppenheimer, 2002, Limited global change due to the largest known Quaternary eruption, Toba ~~ 74 Kyr BP, Quaternary Science Reviews, 21, 1593-1609 ] Some scientists hypothesize the eruption caused an immediate return to a glacial climate regime by accelerating an ongoing continental glaciation, thereby causing massive population reduction among animals and human beings onEarth . Others argue that the climatic effects of the eruption were too weak and brief to impact early human populations to the degree proposed. [ Oppenheimer (2002) ]This, combined with the fact that most human differentiations abruptly occurred at that same period, is a probable case of bottleneck linked to volcanic winters (see
Toba catastrophe theory ). On average, super-eruptions with total eruptive masses of at least 1015 kg (Toba eruptive mass = 6.9 × 1015 kg) occur every 1 million years.Cite Sm| B.G. Mason, D.M. Pyle, and C. Oppenheimer, 2004, The size and frequency of the largest explosive eruptions on Earth, The Bulletin of Volcanology, 66 (8), 735-748. ]Effects on life
The causes of the bottleneck phenomenon, i.e., a sharp decrease in a
species ' population immediately followed by a period of great genetic divergence (differentiation ) among survivors—is attributed to volcanic winters by some researchers. The geologic and genealogical records indicates that the eruption of the super volcano Mt. Toba (nowLake Toba , acaldera ). According to anthropologistStanley Ambrose , such events diminish the population size to "levels low enough for evolutionary changes, which occur much faster in small populations, to produce rapid population differentiation". In the Toba bottleneck, many species show massive effects of narrowing of the gene pool, and it is believed Toba nearly caused mankind to go extinct.References
Further reading
*cite journal | author = MR Rampino, S Self & RB Stothers | year = 1988 | title = Volcanic winters | journal = Annual Review of Earth and Planetary Science | volume = 16 | pages = 73–99 | doi = 10.1146/annurev.ea.16.050188.000445
*C. Oppenheimer, 2002, Limited global change due to the largest known Quaternary eruption, Toba ~~ 74 Kyr BP, Quaternary Science Reviews, 21, 1593-1609.
ee also
*
Nuclear winter
*Climate changes of 535-536
*Year Without a Summer
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