Scientists Issue HIGH ALERT for These 10 American Volcanoes - This Is What You Need to Know!

Something is moving beneath America's volcanoes. At Mount Rainier, USGS recorded the largest earthquake swarm ever detected there. Beneath Mount St. Helens, hundreds of earthquakes have been linked to pressure changes in its magma system. And in Hawaii, scientists are watching the ground repeatedly inflate as magma rebuilds underground. Today on Discover Tube, we're investigating 10 American volcanoes where scientists have detected something fascinating beneath the surface. And number one is behaving unlike anything else on this list. Number 10. Newberry Volcano, Oregon. Central Oregon looks peaceful. But beneath the forest south of Bend sits one of America's largest volcanoes, Newberry Volcano. It's roughly 20 miles across, with a summit caldera containing Paulina Lake and East Lake. And beneath that landscape is still a remarkable amount of heat. Newberry's last known eruption occurred only about 1,300 years ago, producing the big obsidian flow. But the bigger clue is underground. Newberry contains an active geothermal system. Hot groundwater circulates through fractured volcanic rock, and drilling has encountered extremely high temperatures several kilometers beneath the surface. That doesn't mean magma is about to erupt. It means heat from Newberry's volcanic system remains underground. Think of it like heating a pot from underneath. The surface can look completely calm while energy is still moving through the system below. USGS, Cascades Volcano Observatory, monitors Newberry using seismic instruments, GPS, and other techniques designed to detect changes in earthquakes and ground deformation. And that's critical, because volcanic unrest often begins underground long before anything appears at the surface. Newberry is currently quiet. But its heat reminds scientists that the volcano isn't geologically dead. And farther south, California has an even larger volcanic system where earthquakes continue beneath a landscape most people don't even realize is volcanic. Number 9. Lassen Volcanic Center, California. Northern California contains one of America's youngest volcanic landscapes, Lassen Volcanic Center. Lassen Peak famously erupted between 1914 and 1917. Its largest explosion occurred in 1915, producing an eruption column and devastating nearby areas. More than a century later, the region is quiet. But underground, the volcanic system hasn't disappeared. USGS still detects earthquakes around Lassen. In its June 23, 2026 Weekly Update, the California Volcano Observatory reported four earthquakes greater than magnitude 1 near the Lassen Volcanic Center in just one week. The largest reached magnitude 2.4. That isn't unusual enough to indicate an eruption. In fact, USGS classified Lassen as normal-slash-green. But Lassen contains another clue, hydrothermal activity. Fumaroles release steam. Hot springs circulate heated water. Boiling mud pots reveal enormous amounts of thermal energy beneath the landscape. That heat ultimately comes from Lassen's volcanic environment. Water enters fractures. It moves underground. It becomes heated. Then it rises again. The result is a constantly changing underground plumbing system. Earthquakes can fracture rock and change fluid pathways. Minerals can seal old fractures. New pathways can open. And pressure can migrate. But Lassen's underground system is relatively quiet compared with what scientists have documented farther north. Because Number 8 has shown evidence of something much more specific. Magma recharge. Number 8. Mount St. Helens, Washington. Mount St. Helens doesn't need an introduction. On May 18, 1980, a magnitude 5.1 earthquake triggered the largest landslide in recorded history at the time. The volcano's north flank collapsed. Pressure dropped. A devastating lateral blast exploded outward. 57 people died. But Mount St. Helens didn't stop evolving after 1980. Its most recent eruptive period continued from 2004 until 2008. And years later, USGS instruments started detecting another interesting signal underground. Earthquakes. From February 1 through June 17, 2024, scientists located approximately 350 earthquakes beneath Mount St. Helens. Most were tiny. The largest reached only magnitude 2.0. But their location mattered. The median depth was about 3.5 miles below sea level, or roughly 4.6 miles beneath the crater floor. USGS scientists believe these small earthquakes can be associated with pressurization of the volcano's magma transport system. One possible cause is magma recharge. Here's what that means. Magma forms deep beneath the Cascades. At Mount St. Helens, USGS says magma can originate near the base of the crust at roughly 16 miles, or 25 kilometers, depth. It then rises and can accumulate in a shallower reservoir roughly 2.5 to 6 miles below sea level. When new magma enters that reservoir, pressure changes. Rock responds. Small fractures can slip. Earthquakes appear. It's like slowly injecting fluid into a pressurized underground container. Eventually, the surrounding rock feels the stress. But this is extremely important. Magma recharge does not automatically mean an eruption is coming. Mount St. Helens has experienced similar periods before without erupting. Scientists found no significant accompanying changes in ground deformation, volcanic gases, or thermal emissions during the 2024 sequence. So the volcano remained at normal background status. Still, what scientists were detecting was fascinating. Something was changing kilometers underground. And at number 7, the ground itself has provided an even clearer signal. Number 7. Three Sisters, Oregon. Three snow-covered volcanic peaks dominate the skyline of central Oregon. North Sister, Middle Sister, South Sister. But the most interesting feature isn't any of the summits. It's the ground west of them. Around 2001, scientists announced the discovery of something unexpected. Satellite radar measurements showed that an area roughly 10 to 12 miles across was rising. The center of the uplift was located west of South Sister. The discovery attracted immediate scientific attention because volcanoes don't normally inflate without a reason. One interpretation was that magma had accumulated several kilometers underground. Imagine pushing upward against a giant rubber sheet. The pressure is concentrated below one location, but the deformation spreads across a much larger area above it. That's our first comparison. Except here, the sheet is Earth's crust. Scientists used InSAR, Interferometric Synthetic Aperture Radar, to detect tiny changes in the distance between satellites and the ground. GPS stations later improved measurements. Over time, the uplift rate changed. It slowed. But the deformation didn't simply erase itself. Researchers have continued studying the region to understand whether magma, volcanic fluids, or both are responsible. This is exactly why satellite monitoring changed volcanology. Scientists no longer need to wait for smoke. They can sometimes see a volcano breathing from space. If you're enjoying these hidden geological stories, subscribe to DiscoverTube. And here's a question. If the ground beneath a volcano started rising near your city, would you want scientists monitoring every millimeter? Because Number 6 sits much closer to major population centers, and its underground activity recently broke a monitoring record. Number 6. Mount Rainier, Washington. At 14,410 feet, Mount Rainier towers above western Washington. Seattle lies roughly 60 miles away. Tacoma is even closer. Glaciers cover the volcano. Deep valleys extend outward from its slopes. And in July 2025, something unusual started happening beneath its summit. At 1.29 a.m. on July 8th, instruments detected an earthquake swarm. Then more earthquakes followed. And more. By the time the sequence returned to normal, USGS reported more than 1,350 located earthquakes. Thousands of additional earthquakes were too small to locate accurately. It became the largest earthquake swarm ever recorded at Mount Rainier. The average depth was approximately 2.8 miles, or 4.5 kilometers, beneath the summit. The largest event? Only magnitude 2.42. So why did scientists pay attention? Because earthquake swarms can reveal changes underground. Unlike a normal earthquake sequence, where one large event is followed by smaller aftershocks, volcanic swarms can contain many small earthquakes clustered in time and space. At Rainier, however, the evidence didn't point toward rising magma. USGS concluded the 2025 swarm was associated with the volcano's hydrothermal system. That's an important distinction. Rainier contains hot water and volcanic gases underground. Fluids move through cracks. Pressure changes. Fractures respond. Earthquakes occur. Imagine thousands of tiny pressure adjustments inside an underground plumbing network. That's comparison number two. And despite the record-breaking number of earthquakes, USGS kept Rainier at normal-slash-green throughout the swarm. By August 25, 2025, earthquake activity had returned to typical rates. That's what makes volcanic monitoring so important. A dramatic signal doesn't always mean an eruption. Scientists have to determine what caused it. Magma? Water? Gas? Tectonic stress? Sometimes the answer completely changes the threat. And nowhere is that distinction more important than at number five. Number five. Long Valley Caldera, California. Drive through eastern California near Mammoth Lakes and you're traveling across the remains of one of the largest eruptions in North American geological history. Long Valley Caldera. The caldera is roughly 20 miles long and 11 miles wide. It formed about 760,000 years ago during the enormous Bishop Tuff eruption. Hundreds of cubic kilometers of material were erupted. The roof above the magma reservoir collapsed. A giant depression formed. But Long Valley isn't simply an ancient scar. Beginning around 1980, scientists detected renewed unrest. Earthquakes increased. Parts of the caldera began rising. Over subsequent decades, USGS recorded repeated episodes of seismic activity and deformation. That generated an obvious question. Was magma returning? Research increasingly showed the answer was more complicated. A major study published in Science Advances in 2023 used seismic imaging to investigate Long Valley's underground structure. Researchers concluded that recent unrest was more consistent with fluids and gases being released as the magma body cools and crystallizes, rather than evidence that the supervolcano is preparing for a giant eruption. That's fascinating because the surface signal can look alarming. Earthquakes, uplift, gas, hot springs. But those signals don't always mean fresh magma is rapidly rising. A cooling magma body can release fluids. Those fluids increase pressure. Pressure can fracture surrounding rock. Earthquakes follow. Long Valley therefore demonstrates one of volcanology's biggest challenges. Scientists don't simply ask, is the ground moving? They ask, why is it moving? As of June 2026, USGS reported normal background earthquake activity and deformation across California's monitored volcanoes, including Long Valley. But the decades of unrest have given scientists a remarkable window into what happens as a huge volcanic system cools underground. And number four takes that hidden plumbing problem to another level. Number four, Yellowstone. Yellowstone looks like a landscape designed by another planet. Geysers, boiling springs, mud pots, steam vents. And beneath them sits one of the largest hydrothermal systems on Earth. But something happened there again in June 2026. At approximately 5.09 a.m. on June 13th, a hydrothermal explosion occurred in Biscuit Basin. USGS reported that the event happened roughly 100 to 200 feet north of Black Diamond Pool. Rocks were thrown tens of feet into the air. Large amounts of sediment-rich hot water entered the Firehole River. The water became discolored for miles downstream. And yet, Yellowstone was not erupting. There was no evidence of magma suddenly racing toward the surface. Instead, this was a steam-driven explosion. Here's how it works. Water circulates underground through fractured volcanic rock. The deeper it travels, the hotter it becomes. But underground pressure can prevent that water from boiling even above temperatures where it normally would at the surface. Now suddenly reduce the pressure. The superheated water can flash into steam. Steam occupies dramatically more volume than liquid water. Pressure increases explosively. Rock breaks. Material is thrown outward. This is closer to opening an enormously pressurized geological pressure cooker than to a traditional lava eruption. That's comparison number three. Yellowstone demonstrated the danger dramatically in July 2024 when another hydrothermal explosion occurred at Biscuit Basin near Black Diamond Pool. Then another smaller event occurred in June 2026. But here's what the broader monitoring data showed. In June 2026, Yellowstone Volcano Observatory located 118 earthquakes. The largest was magnitude 2.4. USGS also reported no significant uplift or subsidence of Yellowstone Caldera or the North Caldera Rim since January 2026. Alert level, normal. Aviation code, green. That's the strange reality of Yellowstone. The volcano itself can remain at background levels while its hydrothermal system produces sudden local explosions. Most of Yellowstone's spectacular surface features exist because heat is still moving through the crust and the plumbing constantly evolves. Earthquakes open fractures. Minerals seal others. Water changes direction. Steam accumulates. Pressure changes. So Yellowstone's underground world is never completely static. But number three isn't driven primarily by steam. It's a massive Hawaiian volcano where scientists watch magma move through an enormous underground network. Number three, Mauna Loa, Hawaii. Mauna Loa is so large that standing on it can make you forget you're standing on a volcano. It covers more than half of Hawaii Island. From its base on the seafloor to its summit, the entire volcanic structure rises roughly nine kilometers. And beneath it is an active magma system. Mauna Loa erupted in 2022 for the first time since 1984. Before that eruption, USGS scientists detected warning signals. Earthquake rates increased. Ground deformation changed. Magma was pressurizing the summit reservoir. Then, late on November 27, 2022, the eruption began. Lava initially erupted within the summit caldera before migrating into the northeast rift zone. This showed scientists something important. Hawaiian volcanoes aren't simply giant tanks filled with lava. They're networks. Magma moves through reservoirs, cracks, and rift zones. Pressure can shift from one area to another. GPS stations can detect the ground moving by tiny amounts. Tilt meters detect changes in slope. Seismometers detect rock breaking underground. Gas instruments measure emissions. Together, these systems allow the USGS Hawaiian Volcano Observatory to reconstruct what is happening where humans can't see. Mauna Loa has returned to much quieter conditions since 2022. But its enormous size and relatively frequent geological history mean scientists continue watching it constantly. And just southeast of Mauna Loa sits another volcano. One where underground pressure is changing so quickly that scientists have learned to forecast some eruptive episodes from the way the ground reinflates. Number 2. Kilauea, Hawaii Kilauea isn't simply showing signs of underground magma. Scientists are watching the volcano repeatedly fill, erupt, drain, and refill. The current summit eruption began in December 2024. By May 2026, Kilauea had already reached 47 episodes of lava fountaining. By June 27, it reached episode 50. That episode lasted 7 hours. USGS estimated that approximately 4.9 million cubic meters of lava erupted. At peak intensity, lava was being released at roughly 330 cubic meters per second. Then it abruptly stopped. What happened next is the fascinating part. The summit started inflating again. During episode 50, the Uekahuna tiltmeter recorded about 15.3 microradians of deflation. After the eruption ended, inflation resumed. Why? Because magma was once again accumulating underground. This creates a repeating cycle. Magma enters the shallow system. Pressure rises. The summit inflates. Lava fountains begin. Pressure drops. The ground deflates. The fountains stop. Then magma starts rebuilding pressure again. Scientists have become so familiar with this cycle that USGS has been able to estimate windows for when the next lava fountaining episode may begin, based partly on the rate of summit inflation. That's extraordinary. Volcanologists aren't predicting some hypothetical eruption decades away. They're measuring a volcano's underground pressure system almost in real time. During pauses, USGS has also recorded low-frequency seismic pulses associated with processes inside the summit system. Sulfur dioxide continues escaping. Vents continue glowing. Then pressure rebuilds. Kilauea essentially provides scientists with a natural laboratory where magma movement can be watched almost continuously. About three-quarters through our list, here's a question for DiscoverTube. Which signal would concern you most? Hundreds of earthquakes? Rising ground? Or rapidly increasing volcanic gas? Because number one combines underground magma, earthquakes, and one of America's most closely watched volcanic threat. Number one. Mount Spur, Alaska. About 80 miles west of Anchorage stands Mount Spur, and unlike several volcanoes on this list, recent changes here pushed scientists to raise the alert level. The Mount Spur volcanic complex includes a summit vent and a younger vent called Crater Peak. Crater Peak produced explosive eruptions in 1953 and again in 1992. The 1992 eruption sent ash high into the atmosphere and disrupted aviation around Anchorage. Then, decades later, scientists began detecting renewed unrest. Earthquakes increased beneath the volcano. The ground began deforming. Volcanic gases changed. Heat appeared in the summit crater lake. These signals indicated that something had changed underground. The Alaska Volcano Observatory, operated by USGS, the University of Alaska Fairbanks Geophysical Institute, and the Alaska Division of Geological and Geophysical Surveys began tracking the unrest closely. Why are these signals so important together? Because one volcanic signal can have multiple explanations. Earthquakes alone might represent shifting fluids. Ground deformation alone can have different causes. Gas changes alone don't guarantee an eruption. But when several independent monitoring systems begin changing together, scientists pay much closer attention. Seismic instruments can reveal rock breaking. GPS can show the volcano swelling. Gas measurements can reveal material escaping from magma. Satellite instruments can identify thermal changes. Put those together and scientists can begin reconstructing what's happening kilometers below the surface. This is essentially volcanic detective work. And Alaska makes that work especially important. The state contains more active volcanoes than any other part of the United States. Many sit directly beneath major North Pacific aviation routes. An eruption doesn't need to bury anchorage in lava to create a major problem. Volcanic ash can enter the atmosphere. Jet engines ingesting ash can be damaged or even lose power. Flights may have to reroute across enormous distances. That's why Alaska Volcano Observatory doesn't only monitor lava. It monitors ash clouds, earthquakes, gas, ground deformation, satellite temperatures, and infrasound. Mount Spur reminds us why volcanic unrest has to be interpreted carefully. A volcano can become restless and then calm down without erupting. Or underground signals can continue evolving until magma finally reaches the surface. Scientists cannot simply look inside the volcano. They have to reconstruct the hidden system from the signals escaping it. And that's what connects every volcano on this list. Conclusion. Newberry has enormous underground heat. Lassen has an active hydrothermal system. Mount St. Helens has shown earthquakes associated with pressurization and possible magma recharge. Three Sisters has experienced measurable uplift. Mount Rainier produced more than 1,350 located earthquakes during its record 2025 swarm. Long Valley has spent decades deforming and releasing fluids above a cooling magma system. Yellowstone produced another hydrothermal explosion in June 2026. Mount Aloha showed how underground pressure can precede eruption. Kilauea is repeatedly inflating and deflating as magma enters and leaves its summit system. And Mount Spur has shown how scientists combine earthquakes, deformation, gas and heat to understand volcanic unrest. But none of these signals should automatically be translated into one sentence. An eruption is coming. That's not how volcanology works. Earthquakes can come from magma, water, gas or tectonic stress. Uplift can indicate magma or pressurized fluids. Hydrothermal explosions can occur without a new magmatic eruption. And magma itself can accumulate underground for years without reaching the surface. That's why organizations like the USGS Cascades Volcano Observatory, Yellowstone Volcano Observatory, California Volcano Observatory, Alaska Volcano Observatory and Hawaiian Volcano Observatory use entire networks of instruments. A single seismometer gives scientists one clue. A network gives them a three-dimensional pattern. A GPS station shows movement. Satellite radar shows how far that movement extends. Gas instruments reveal what's escaping from below. Thermal cameras reveal heat. And when those signals are combined, scientists can sometimes determine whether magma is rising, pressure is changing or underground water is simply finding a new route. The volcano we see above ground is only the surface. Most of the real story happens kilometers below our feet. So which American volcano should DiscoverTube investigate in a full documentary next? Mount Rainier? Yellowstone? Mount St. Helens? Kilauea? Or one we didn't include? Leave your choice in the comments. Subscribe to DiscoverTube for more science, geology and volcano documentaries. And we'll see you in the next one.