In short, knowing if a volcano is active, dormant, or extinct is complicated and all comes down to timing. As such, some volcanologists refer to extinct volcanoes as inactive, and some volcanoes once thought to be extinct are now referred to as dormant. Edinburgh Castle, located just outside the capitol of Edinburgh, Scotland, is famously located atop an extinct volcano.īut of course, determining if a volcano is truly extinct is often difficult, since some volcanoes can have eruptive lifespans that measure into the millions of years. There are many examples of extinct volcanoes around the world, many of which are found in the Hawaiian-Emperor Seamount Chain in the Pacific Ocean, or stand individually in some areas.įor example, the Shiprock volcano, which stands in Navajo Nation territory in New Mexico, is an example of a solitary extinct volcano. Geologists also employ the category of extinct volcano to refer to volcanoes that have become cut off from their magma supply. Compare that to Mount Grímsvötn in south-east Iceland, which erupted three times in the past 12 years (in 2011, 20, respectively).Īnd so a dormant volcano is actually part of the active volcano classification, it's just that it's not currently erupting.Īleutian island #volcano letting off a little steam after the new year on Jan 2, 2016. Prior to this, the volcano was thought to be extinct since it had not erupted for over 10,000 years. The same is true of the Fourpeaked Mountain eruption in Alaska in 2006. For instance, the volcanoes of Yellowstone, Toba, and Vesuvius were all thought to be extinct before their historic and devastating eruptions. Nevertheless, volcanoes may remain dormant for a long period of time. Volcanoes are often considered to be extinct if there are no written records of its activity. Here too, definitions become complicated since it is difficult to distinguish between a volcano that is simply not active at present, and one that will remain inactive. Meanwhile, a dormant volcano is used to refer to those that are capable of erupting, and will probably erupt again in the future, but hasn't had an eruption for a very long time. Another means for determining if a volcano is active comes from the International Association of Volcanology, who use historical time as a reference (i.e. The Smithsonian Global Volcanism Program defines a volcano as active only if it has erupted in the last 10,000 years. unusual earthquake activity or significant new gas emissions) that mean it is about to erupt. Hence why scientists often consider a volcano to be active only if it is showing signs of unrest (i.e. In the past few thousand years, many of Earth's volcanoes have erupted many times over, but currently show no signs of impending eruption.Īs such, the term "active" can mean only active in terms of human lifespans, which are entirely different from the lifespans of volcanoes. Volcanoes – like all geological features – can have very long lifespans, varying between months to even millions of years. But in the end, knowing the difference all comes down to timing!Ĭurrently, there is no consensus among volcanologists about what constitutes "active". Those that erupt regularly are called active, while those that have erupted in historical times but are now quiet are called dormant (or inactive). Put simply, the most popular way for classifying volcanoes comes down to the frequency of their eruption. But what exactly is the differences between the two, and how do geologists tell? This is actually a complicated question, because there's no way to know for sure if a volcano is all done erupting, or if it's going to become active again. Such is the nature of volcanoes, and is the reason why we distinguish between those that are "active" and those that are "dormant".
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