Before 1980, experts considered Mount St. Helens in Washington a dormant volcano, since its last period of volcanic activity was in the mid-1800s. Then, on a fateful day in May, the volcano erupted and left fifty-seven people and billions of dollars in damage in its wake. A similar situation occurred in southern Chile after the Chaitén erupted in 2008, following a nine-thousand-year period of dormancy. And in 2010, Iceland’s Eyjafjallajökull volcano, one of the biggest in the country, erupted for the first time in two hundred years.
Clearly, the line between dormant and active can change at any moment. The definitions of these terms vary, even among volcanologists: some say “active” means eruption within the past ten thousand years, while others define it as activity within historic time. At its most basic, a dormant volcano is one that hasn’t erupted in a considerable amount of time, but is expected to at some point. Numerous volcanoes all over the world fit into this category, though, judging by the previous examples, that classification is clearly subject to change.
Photo source: Spencer Critchley (cc)
Hawaiian for “White Mountain,” it’s the tallest of the five volcanoes located on the Big Island of Hawaii. Mauna Kea last erupted around 2460 BC, but that doesn’t mean it won’t happen again in the future, especially if multiple earthquakes happen in the area.
Photo source: Rei-artur (Wikimedia Commons)
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