We humans have long been wary of volcanoes, and with good reason. We can’t hear about Vesuvius’ victims in the ancient Roman city of Pompeii or hear about the wide-ranging aftereffects of Indonesia’s Mount Tambora eruption in 1815 — one of the most monstrous volcanic eruptions in recorded history — without feeling a little nervous.

So, we humans keep a list of worrisome volcanoes to keep tabs on and study — they’re called the Decade Volcanoes, but not because they erupt every decade.

“The so-called Decade Volcanoes project was an initiative that began in the 1990s as part of the United Nations International Decade for Natural Disaster Reduction,” says Jon Major, lead scientist at the Cascades Volcano Observatory in Vancouver, Washington. “As part of that proposed initiative, the international volcano community, through an organization called International Association of Volcanology and Chemistry of the Earth’s Interior (IAVCEI), identified 16 volcanoes worldwide as being worth more intensive study, owing to their history of destructive eruptions, the hazards they posed and their proximity to densely populated areas.”

Volcanologists use a variety of tools to assess the state of a volcano. They watch for earthquakes using seismometers, monitor for changes in ground surface elevation using GPS and satellite radar technology, and keep an eye on the release of volcanic gases that may indicate the movement of magma toward the surface.

“This instrumentation network allows us to detect the earliest possible signs of potential volcanic activity so that we can inform emergency management authorities and the public,” says Major.

Here, in alphabetical order (and not order of destructive potential), are the 16 Decade Volcanoes: