© ReutersThe legacy of the ash and dust thrown up by the Puyehue-Cordon Caulle volcano in Chile may well live on.
The longer-term effects of all this ash and dust could be of wider environmental concern than, say, a few hundred thousand stranded passengers, as difficult as it is for those people.
Volcanic eruptions are awesome spectacles. In part this is due to millions of tonnes of tiny ash and dust particles, known as volcanic aerosols, being blasted high into the air. We've all marvelled at the photographs.
In volcanic terms, the ash and dust plume created by Puyehue-Cordon Caulle was modest, only reported to have reached a height of around 15 kilometres. Large explosions, such as the 1991 eruption of Mount Pinatubo in the Philippines, can create plumes in excess of 34 kilometres high and 400 kilometres wide, ejecting more than 17 million tons of aerosols.
But even as a modest eruption, the Chilean volcano could have ejected enough ash and dust into the stratosphere to have some long-term climatic effects, which could in turn affect agriculture and impact on human wellbeing and quality of life.
The reason is that large volumes of aerosols can, depending on how high they 'sit' in the air and how long they remain there, have a measurable cooling effect. The higher the dust gets into the atmosphere and the more of it there is, the greater its capacity to reflect heat from the sun, which cools the land below.
This phenomenon has been observed before, and not just from volcanic eruptions. In the late-1990s forest fires in Indonesia caused local crops to fail as smoke and dust from the fires stayed in the atmosphere and filtered out the sun's heat.
Their effect on weather variations and crop failures have been documented on a global scale over hundreds of years. Following the massive eruption of Indonesia's Tambora volcano in 1815, farmers as far away as the northeastern states of the US America reported devastating frosts during spring, the Chinese recorded unusual weather variations, and crops failed across Europe, resulting in famine.
Going back further, there are theories that another Indonesian eruption that occurred around 70,000 years ago, known as the Toba super-eruption, was responsible for wiping out species and plunging virtually the entire planet into a winter lasting several years.
It is possible that the Puyehue-Cordon Caulle eruption, in conjunction with recent eruptions in Iceland and other parts of the world could, to a measurable extent, result in some cooling, which in the short term may be seen to offset the warming effects of climate change in some geographic areas.
One interesting thing to point out, however, is that unlike the organic-based material spread about by dust storms and forest fires, the plumes created by volcanoes have literally been blasted out of the ground and incinerated. We can at least be thankful that this fiery process ensures the resultant aerosols do not contain any bacteria which, if borne on the air to new environments, could have even greater impacts on ecosystems.
Nigel Tapper is Professor of Environmental Science, School of Geography and Environmental Science at Monash University.
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