Sunday, October 26, 2014

How Many Volcanoes?

How many of X are there in the world? This is a common question that often provides a surprising answer. You might be surprised at how many drill rigs exist or once existed in the Gulf of Mexico, for instance (over 4,200!).

Q: how many volcanoes are there in the world?
- Josh S

A: The Global Volcanism Program of the Smithsonian Institution lists 1559 volcanoes with eruptions happening during the Holocene period (the last 10,000 years). This means they are listing active or potentially active volcanoes. There are MANY more volcanoes in the world than that, of course. Some of them are just older and long inactive, like parts of Craters of the Moon national monument in Idaho (however some features there are as recent as 2,000 years ago), or volcanoes that erupted in Venezuela over a billion years ago. Some volcanic features that are not on the Smithsonian volcano database are just too small to easily list. While serving as the chief scientist for volcano hazards in the US Geological Survey, I assigned one of my senior scientists to do a full assessment and summary of the Cascades volcanoes of Washington, Oregon, and California. I thought there might be 15 volcanoes there. He ended up with a list of over 3,500 - because he counted every focal point of volcanic activity including small scoria cones and maars.