Mount Spurr, Alaska’s snow-covered stratovolcano just 77 miles from Anchorage, has been rumbling with small earthquakes since April 2024, raising concerns among scientists at the Alaska Volcano Observatory (AVO). These tremors could signal that magma is on the move beneath the surface, potentially setting the stage for an explosive eruption. But what does this mean for Alaska—and could this icy giant really wake up?
What’s a Stratovolcano, Anyway?
Stratovolcanoes, like Mount Spurr, are the rock stars of the volcanic world. Known for their steep, cone-shaped profiles, they’re built over thousands of years by layers of lava, ash, and volcanic rock. Unlike the gentler, lava-oozing shield volcanoes of Hawaii, stratovolcanoes are notorious for their explosive eruptions. Their thick, gas-rich magma can clog volcanic vents, building pressure until—boom—it erupts, sending towering ash columns and deadly pyroclastic flows racing down the slopes.
Think Mount Fuji or Mount St. Helens. Mount Spurr is in the same league, making it a potential threat if its current seismic activity leads to an eruption.
Mount #Spurr update: On Dec 18, an AVO crew conducted a gas and observation flight to measure volcanic gases (H2O, SO2, CO2, H2S) and do a photo survey of the summit and Crater Peak. Enjoy this video taken during the flight! (1/2) pic.twitter.com/8GmfSY8U2l
— Alaska AVO (@alaska_avo) December 26, 2024
Earthquakes and Magma: A Dangerous Combo
According to Matt Haney, a scientist at the AVO, Mount Spurr has been experiencing more earthquakes than usual for months, but things have gotten even more intense recently. The quakes have shifted from the volcano’s summit to an area about 2 miles downhill, near a side vent called Crater Peak. This spot has erupted twice before—in 1953 and 1992—sending ash columns 65,000 feet into the sky and blanketing Anchorage in a fine layer of volcanic dust.
Is an Eruption Imminent?
Not necessarily. Scientists say there are three possible scenarios:
- Crater Peak Eruption (50% chance): This could unleash ash clouds, pyroclastic flows (superheated gas and rock moving at 200+ mph), and lahars (volcanic mudflows) from melting snow and ice.
- No Eruption: The magma might stop moving, and the shaking could calm down, as it did in 2004 and 2005.
- Summit Eruption (unlikely): The main crater hasn’t erupted in 5,000 years, so this is the least probable outcome.
What’s at Stake?
The good news? No communities are in the direct path of potential pyroclastic flows or lahars. The real concern is ashfall. During the 1992 eruption, Anchorage’s airport shut down, and the city was dusted with 3 millimeters of ash, disrupting air travel and daily life. Today, Anchorage’s airport handles even more flights, including key routes between North America and Asia, so the impact of a similar eruption could be even worse.
When Could It Happen?
Before the 1992 eruption, Mount Spurr gave a clear warning: three weeks of constant seismic tremors, known as volcanic tremor, signaled that magma was rising to the surface.
“If we detect sustained tremor in our seismic data, it would be a clearer sign that an eruption is more likely,” Haney explained.
What’s Next for Mount Spurr?
For now, scientists are keeping a close eye on the restless giant. Mount Spurr could erupt tomorrow, next year, or not at all. But its history and current activity remind us that nature always has the final say.
This article was originally written in Spanish by Natalia Rodríguez in Ecoosfera.