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It may seem that there has been an unusual amount of volcanic activity lately, with major eruptions occurring in Iceland, Guatemala and Ecuador. But is it really unusual, and are the eruptions connected?

The short answer to both questions is no.

Guatemala's Pacaya volcano and Ecuador’s Tungurahua vociferously erupted on Thursday, wreaking havoc on villages and cities nearby.

When an Icelandic volcano with a nearly unpronounceable name erupted after 200 years of quiet in March, it was little more than a curiosity. But when it erupted again in April — this time spewing huge clouds of ash as high as 11 kilometers into the stratosphere, quickly choking airways across Europe and costing airlines billions of dollars — it captured the world’s attention. As the ashfall decreased and airlines resumed normal routes this week, the headlines began to fade.

You never quite know when a given volcano is going to erupt — but you can bet on it. Ireland’s biggest bookmaker, Paddy Power, jetted to fame among geologists in early January, when it announced its latest novelty bet: which of a handful of famous volcanoes around the world would be the next to powerfully erupt.

Blogging on EARTH: Iceland links and Volcanoes 301

There's a lot of great info out there about the Iceland eruption's geology, if you know where to link.

When Iceland’s Eyjafjallajokull volcano began erupting March 20, few people expected it to wind up wreaking havoc on the world’s travel. Yet that’s what it has done, as the eruption has ramped up in the last few days and is now spewing steam and ash several kilometers into the air. The winds over the North Atlantic have blown the ash cloud over Northern Europe, grounding tens of thousands of flights for myriad reasons, not the least of which is that ash can clog jet engines, causing them to fail.

For more than 9,000 years, Chaitén volcano quietly towered 1,122 meters over southern Chile. The volcano seemed almost asleep: Its wide crater, shaped by layers of ash and pumice from an ancient eruption, held two lakes and a giant dome of obsidian — the same glossy black rock that was used in prehistoric times to shape artifacts found at archaeological sites as far as 400 kilometers away. Almost at the foot of the volcano, just 10 kilometers to the southwest, a small village grew into the town of Chaitén, population 4,200.