Lyn Topinka/USGS
Of these, 18 are "Very High Threats"- volcanoes that, were they to erupt, could disrupt air travel and threaten people's lives.
A caveat: this is not a ranking of the volcanoes by their danger level.
As Wendy Stovall, a geologist with USGS, told Business Insider in an e-mail:
There are many volcanoes that are threatening due to factors such as tectonic setting, population density, eruption frequency, and potential to erupt again. The variations in these factors make each of the ... 'high threat' volcanoes uniquely dangerous.
Since they pose such substantial threats, we figured we should get to know them a little better. So, here are the 18 most dangerous volcanoes in the US.