An aerial view of the Crater Lake Caldera in Oregon. Marli Miller/UCG/Universal Images Group via Getty ImagesShareThough immensely powerful, volcanoes are not always spewing hot lava around. Many are considered dormant or even extinct and have not shown their strength for hundreds of thousands of years in some cases. However, a team of scientists recently found magma chambers lurking beneath six volcanoes in the Cascade Range. The findings published January 23 in the journal Nature Geoscience are challenging the idea of what separates an active volcano from a dormant one. Get the Popular Science newsletter Breakthroughs, discoveries, and DIY tips sent every weekday. By signing up you agree to our Terms of Service and Privacy Policy.Active vs. dormant volcanoesObviously, visible lava spewing from a volcanos caldera, like Hawaiis Mount Klauea or Grimsvtn in Iceland, indicates that a volcano is active. However, not all active volcanoes are erupting. They have the potential to erupt in the future with young and fresh magma chambers.According to the U.S. Geological Survey (USGS), a dormant volcano is one that is not erupting now. However, they could still erupt in the future. Some volcanologists will use the qualifier long-dormant system to refer to a volcano that has not erupted in thousands of years. A recently active system might have erupted a few years or decades or centuries ago. What makes it dormant versus potentially active is that its large magma bodies have typically been expelled during eruptions and have dissipated over time. Mount Kilimanjaro in Tanzaniawhich last erupted about 360,000 years ago and Japans Mount Fuji317 years agoare both currently considered to be dormant volcanoes.However, new research is challenging these definitions.The magma beneathIn the new study, a team from Cornell University and the USGS studied six volcanoes of various size and dormancy status within the Cascade Range in the northwestern United StatesLassen Peak, Crater Lake, the Newberry Volcano, Mount Hood, Mount St. Helens, and Mount Rainier. Seismic waves identified persistent and large magma chambers in all of the volcanoeseven the dormant ones. According to the team, these results were surprising since some of the volcanoesincluding the Crater Lake volcano in Oregonhave not been active for thousands of years.Regardless of eruption frequency, we see large magma bodies beneath many volcanoes, Guanning Pang, a study co-author and Cornell University postdoctoral researcher, said in a statement. It appears that these magma bodies exist beneath volcanoes over their whole lifetime, not just during an active state.Observing that more volcanoes have sustained magma bodies is an important factor for researchers that monitor and predict future volcanic activity. As part of the National Volcano Early Warning System, the USGS has spent time expanding and upgrading volcanic monitoring networks within the Cascade Range and elsewhere. The goal is to detect the signs and signals of an impending eruption as early as possible to give people ample warning.[ Related: Extinct volcanoes could hold rare earth elements. ]We used to think that if we found a large amount of magma, that meant increased likelihood of eruption, Pang said, but now we are shifting perception that this is the baseline situation.These results suggest eruptions do not always completely drain a magma chamber. Instead, it will release some of the excess volume and pressure. The magma chamber can then be slowly expanded and refilled over time as the crust melts gradually.If we had a better general understanding of where magma was, we could do a much better job of targeting and optimizing monitoring, study co-author and Cornell geophysicist Wiliam Abers said in a statement. Abers also noted that there are a, great many volcanoes that are sparsely monitored or have not been subject to intensive study.A portable methodAdditionally, the team found that they could use fewer tools to recover this important data. They used a very small network of seismometers situated around each volcano in the study and leveraged some of the recent upgrades made to seismic broadband stations near Cascade Range volcanoes. They then applied a technique that uses scattered wavefields from distant earthquakes, to create detailed subsurface images.Previously, imaging methods required deploying tens to hundreds of seismometers around a volcano, making for a challenging undertaking, Abers said.Plans to expand the magma monitoring system to see if the same discovery in the Cascades can be applied elsewhere are already in the works. One of those locations is Alaska, home to over 130 volcanoes, 90 of which have been active within the last 10,000 years.Our method is very portable and can be used at many if not most other volcanoes around the world, with just a small number of modern seismographic stations, Abers said. We think it can help systemize volcano studies, and provide a key piece of global frameworks for volcanic hazard assessment.