A major eruption could result in large parts of Iceland being flooded as snow and ice melted; significant poisoning of Icelandic agriculture; destruction of property; and, of course, the grounding of aircraft across Europe.
If enough material is ejected it could even have a cooling effect on the global climate for a few years. A precedent for that would be the 1783-84 eruption from the fissure of Laki, which is part of the same volcanic system, Grimsvotn, that erupted last year. This was a very large eruption of 15 cubic kilometres (3.6 cubic miles), compared to the fraction of a cubic kilometre ejected in 2010, and had a huge impact on the northern hemisphere, reducing temperatures by up to 3 degrees C. This had catastrophic effects far beyond the shores of Iceland (where at least a fifth of the population died), with thousands of recorded deaths in Britain due to poisoning and extreme cold, and record low rainfall in North Africa.
Large eruptions such as this occur only every few hundred years on Iceland, but the potential for danger is significant. Even if deaths from famine are less likely today, a recent study of the potential effects of the air pollution caused by such an eruption estimates that it could lead to between 52,000 and 228,000 fatalities throughout Europe.
Meanwhile, nearby Hekla has erupted about once every 10 years in recent times, with the last being in 2000. Similarly, volcanoes beneath the largest ice cap, Vatnajokull, are entering a period of increased volcanic activity – the peak of a 140-year cycle.
This trend is being exacerbated by climate change. Vatnajokull has lost an estimated 400-billion tonnes of ice since the end of the 19th century. This has reduced the pressure on the hot mantle material beneath the crust, leading to increased magma generation. At the end of the last ice age, this same effect led to eruption rates some 30 times higher than at present. The current rate of ice loss is much lower than then, but we can still expect the formation of extra magma equivalent to that which erupted from Eyjafjallajokull in 2010 every 10 years or so.
Nevado del Ruiz volcano (Colombia): Red Alert declared
The Colombian authorities have declared a red alert for the area around the volcano Nevado del Ruiz and warn the population against the feared mud flows (lahars) that are to be expected in an eruption of the volcano. The status of the volcano itself is described as eruption likely in the coming days or weeks.
The reason is a steady increase in seismic activity and gas emissions from the summit crater. In recent days, more and more, usually small earthquakes have been occurring at shallow depths under the volcano, some of them felt. A steam nd gas plume is rising from the crater to 1.5 km and sulfur smell can be noticed in nearby villages and towns.
430 000 inhabitants from the valleys of the Río Chinchina, Manizales and four other rivers have been warned of mud flows and possible floods, which could be triggered especially during heavy rains, even when there is no eruption.
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