13 American Volcanoes Closely Monitored for Sudden Eruptions

The United States is not only cities and wide-open spaces—beneath many iconic landscapes lie active volcanic systems. While catastrophic events are rare, several U.S. volcanoes remain capable of erupting with little warning. Scientists closely monitor these sites to protect communities, aviation and infrastructure.

Why monitoring matters

Volcanic hazards range from slow-moving lava flows to sudden explosive eruptions that produce ash, lahars (volcanic mudflows), and regional disruption. Continuous observation by agencies such as the U.S. Geological Survey (USGS), the Alaska Volcano Observatory (AVO) and the Hawaiian Volcano Observatory (HVO) helps detect precursors—seismicity, ground deformation, gas emissions and hydrothermal changes—that signal unrest.

Volcanoes to watch

Yellowstone Caldera (Wyoming)

Yellowstone sits atop one of the planet’s largest volcanic systems. A supereruption is considered unlikely in our lifetimes, but the region produces frequent seismic and hydrothermal activity. Scientists focus on monitoring ground deformation, earthquakes and gas emissions to detect changing conditions.

Mount St. Helens (Washington)

Famous for its 1980 catastrophic eruption, Mount St. Helens remains active. Its history transformed volcanic monitoring and emergency planning, and it continues to produce seismic swarms, steam emissions and occasional ash events that are closely observed.

Mauna Loa (Hawaii)

The world’s largest active volcano, Mauna Loa produces large effusive eruptions and extensive lava flows. HVO monitors it with satellites, GPS, gas sensors and seismographs to give early warning and help protect communities on the island.

Mount Rainier (Washington)

A snow- and ice-covered stratovolcano, Rainier poses significant lahar and ash hazards to nearby towns. Its potential for explosive behavior and destructive mudflows makes it a priority for monitoring and community preparedness.

Mount Shasta (California)

Part of the Cascade Range, Mount Shasta has produced explosive eruptions in the past. Its elevation and proximity to populated areas require careful observation for seismic and volcanic unrest.

Mount Hood (Oregon)

Mount Hood has been relatively quiet for centuries but still shows minor seismicity. Glaciers on the volcano increase the risk of lahars during eruptive or collapse events, so regional monitoring and preparedness are important.

Kīlauea (Hawaii)

Kīlauea is among Earth’s most active volcanoes and regularly reshapes Hawaii’s landscape with effusive lava flows. Although typically non‑explosive, its eruptions can destroy property and alter coastlines; gas emissions and lava advance are tracked continuously.

Lassen Peak (California)

Within Lassen Volcanic National Park, Lassen Peak erupted in the early 20th century and the area still shows geothermal activity like boiling springs and fumaroles. Ongoing study helps park managers and visitors understand potential hazards.

Mount Baker (Washington)

Steam emissions and hot springs attest to Mount Baker’s vigor. The volcano has experienced both explosive and effusive episodes in the past, so USGS and partners maintain surveillance using seismic and remote sensing tools.

Mount Katmai / Novarupta region (Alaska)

Katmai is tied to the 1912 Novarupta eruption—the largest of the 20th century—which created the Valley of Ten Thousand Smokes. While Katmai itself has been quieter since, the region’s history underscores the potential for large, landscape‑altering eruptions.

Long Valley Caldera (California)

Formed by a massive eruption about 700,000 years ago, Long Valley remains geothermally active with hot springs and unrest episodes. Seismic swarms and ground deformation there are closely monitored because of nearby communities and infrastructure.

Mount Redoubt (Alaska)

Redoubt has produced notable eruptions in recent decades (for example, 1989 and 2009) that injected ash into flight paths and reduced air quality. AVO watches Redoubt with dense monitoring networks to provide timely warnings.

Mount Cleveland (Aleutian Islands, Alaska)

One of the Aleutians’ most frequently erupting volcanoes, Cleveland often erupts with little warning. Its remoteness necessitates reliance on satellite imagery and seismic telemetry; ash clouds from Cleveland can threaten trans‑Pacific aviation.

What you should know

Large, catastrophic eruptions are rare, but smaller or moderate eruptions can still cause serious local disruption and hazards to aviation. Monitoring, public education, and emergency planning remain the best defenses. If you live near or visit volcanic areas, follow guidance from local authorities and official observatories.