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Environmental Influences Affecting Volcanos / Vulcanism

Mighty_Emperor

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Its been known for a while that major influences on the lithosphere (like loading and unloading of ice at the beginning and end of an Ice Age - pos. leading to the saw tooth pattern we see) but this is a much more minor inlfuence - very interesting stuff (and possibly help in eruption prediction?):

Nice day for an eruption

We know that dust from volcanic explosions can chill our climate. Now, Bill McGuire reports, it's becoming clear that weather and changing sea levels can squeeze out lava

Thursday May 6, 2004
The Guardian

Large volcanic blasts can have a dramatic effect on the global environment, pumping enormous quantities of gas into the atmosphere that block solar radiation and lead to significant cooling at the Earth's surface. But can the opposite happen? Can changes in the environment trigger volcanic eruptions?

Research published last week in the Journal of Geophysical Research is the latest to suggest this can and does happen. Ben Mason, David Pyle and colleagues at Cambridge University examined the timings of more than 3,000 eruptions that occurred across the globe between 1700 and 1999. Their surprising findings reveal that the timing of volcanic activity is not random, but clustered, with more eruptions happening between November and March. Recognition of this seasonal behaviour provides the latest piece in a jigsaw, which is likely to show that changes in the environment, such as weather, climate and sea level, exert at least as great an influence on volcanos as volcanos do on the environment.

Explosive eruptions influence the environment by ejecting large volumes of sulphur dioxide gas into the atmosphere, there combining with water to form a veil of tiny sulphuric acid particles known as aerosols. Draped over the stratosphere, this veil absorbs the sun's rays or reflects them back into space, reducing temperatures at the surface.

The titanic explosion of Tambora, Indonesia, in 1815 - probably the largest eruption of the last millennium - was followed by a global cooling of 0.7C and 12 months of haywire weather in Europe and North America. The 1991 Pinatubo eruption in the Philippines spun off a cloud of gas that enveloped the planet in weeks, bringing down temperatures by about 0.25C. Going much further back in time - some 74,000 years - the most cataclysmic volcanic blast known, which made a crater 100km across at Toba in northern Sumatra, is charged with plunging the planet into a "volcanic winter", which according to some, may have presented our distant ancestors with a battle for survival.

The ways in which the environment may influence the activity of volcanos are less well understood, and there are many candidates. At ice-bound volcanos in high-latitude countries such as Iceland, for example, rapid melting at the end of the last ice age promoted the expulsion of magma that had previously been suppressed by the weight of the overlying ice.

Also, the eruptions of the Pavlof volcano on the Alaskan peninsula seem to be controlled by the weather. Low-pressure storm systems crossing the volcano in winter allow the sea beneath to rise by about 30cm (1ft), the extra weight of the water being sufficient to stress the volcano and squeeze out the magma. Looking back over the past few hundred thousand years, sea level seems to have played a key role in persuading volcanos to explode.

A decade ago, I led a team of European scientists looking for a relationship between the timing of volcanic eruptions in the Mediterranean region and the huge - up to 130m (427ft) - changes in sea level that accompanied the formation and melting of the ice sheets during and after the last ice age. The results of the study were clear, with more explosive blasts occurring when sea level was changing most rapidly - either up or down.

A number of explanations for the relationship were explored, including the promotion of eruptions due to weakening and collapse of the flanks of coastal and island volcanos, due to rapid erosion when sea levels were rising fast or a debuttressing effect when sea levels experienced dramatic falls. The most likely answer, however, is more straightforward. As water was repeatedly locked up and released from the ice sheets, so the resultant falls and rises in ocean volumes and sea level stressed the crust beneath volcanos that occupy the margins of the continents. This was able either to allow fresh magma to enter a volcano from deeper within the Earth, or to promote the release of magma already stored within a volcano that was primed and ready to explode.

Alternatively, shifting such huge masses of water about may have been sufficient to stress the crust of the entire planet, either by incrementally changing its shape or by causing tiny variations in the rate of spin. Either way, the incredibly dynamic relationship between melting and freezing ice sheets and rising and falling sea levels appears to have been a major influence on the timing of volcanic eruptions until just a few thousand years ago.

With sea level pretty much stable for the past couple of millennia, the findings of Ben Mason and his colleagues come as a bit of a surprise, until, that is, one considers that ocean waters are still sloshing around en masse.

Although admittedly on a smaller scale than during an ice age, trillions of tonnes of water are still shifted about every year between the hemispheres and from the ocean basins to the margins of the continents, in accordance with the seasons. These redistributions of mass seem to be sufficient to deform the Earth's crust and stress volcanos in such a way as to encourage eruption.

In central America, along the Alaskan peninsula and in Kamchatka (eastern Russia), the number of eruptions peaks when regional sea-level is falling, while the volcanos of Melanesia in the south-west Pacific show a preference for erupting when the regional sea level is at its highest and atmospheric pressure is falling. Globally, the observed increase in the number of eruptions during the winter months amounts to 18%.

Whether the effect is confined to the continental margins and island chains where 95% of active volcanos reside, or occurs planet-wide, the findings have worrying implications for the coming century - when sea level is expected to rise by up to 88cm (2.9ft). Perhaps we and our descendants will face not just a warmer future but a fiery one.

· Bill McGuire is Benfield professor of geophysical hazards and director of the Benfield Hazard Research Centre at University College London. His book, A Guide to the End of the World: Everything you Never Wanted to Know, is published by Oxford University Press

http://www.guardian.co.uk/life/feature/story/0,13026,1210060,00.html

Emps
 
An eruption of good/bad news.

There are few forces on Earth more powerful than a large volcanic eruption.

At their most potent, volcanoes inject millions of tons of Sun-blocking particles high into the atmosphere that can cool Earth for nearly 5 years, endangering crops and leading to “years without summer.” The most recent, the Philippines’s Mount Pinatubo eruption in 1991, caused a temporary 0.5°C drop in global temperatures.

Yet it’s become increasingly clear that even these monumental forces are being altered by human-driven climate change. Declining ice cover can trigger more frequent eruptions near the poles, in Iceland and elsewhere. And an increasingly layered ocean will allow more volcano-induced cooling to linger at Earth’s surface. Now, a new study suggests increased greenhouse gases will help the plumes from large eruptions reach higher, spread faster, and reflect more sunlight, causing more abrupt and extreme cooling.

Before humanity started in on its planet-altering course, volcanoes were one of the biggest climate players. Over the long term, they belched carbon dioxide from Earth’s interior, causing warming. But in the short term, their sulfur gases often react with water to form highly reflective particles called sulfates, triggering spells of global cooling. Dark smudges of ash littering ice cores—our best evidence of these early eruptions—are a dim reflection of the wild weather left in their wake. ...

https://www.sciencemag.org/news/2021/08/massive-volcanoes-could-cool-earth-more-warming-world
 
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