Increased likelihood of eruption at Mount Spurr, Alaska
The likelihood of an eruption at Mount Spurr has increased with gas emissions recorded on March 7 and 11, confirming ongoing volcanic unrest. The volcano is located about 120 km (75 miles) west of Anchorage (population 286 000), Alaska.
Mount Spurr from the southeast during overflight on March 11, 2025. Crater Peak (lower left) and the summit (middle right) are both visible with a gas plume emanating from the summit. Image credit: AVO
The likelihood of a Mount Spurr eruption has risen, with gas emissions detected on March 7 and 11 confirming ongoing unrest. Increased seismic activity, ground deformation, and elevated sulfur dioxide (SO2) and carbon dioxide (CO2) levels suggest a possible eruption in the coming weeks or months.
The Alaska Volcano Observatory (AVO) has maintained an Advisory Alert Level, with an Aviation Color Code of Yellow, signaling heightened unrest but no immediate eruption.
AVO conducted an overflight to measure gas emissions and surface conditions on March 11. The results confirmed a substantial increase in SO2 and CO2 emissions, with SO2 levels reaching 450 metric tons per day, a sharp rise from less than 50 metric tons per day recorded in December 2024. The Crater Peak vent, historically the source of all known eruptions, exhibited high CO2 concentrations.
More than 100 earthquakes per week have been recorded beneath the volcano over the past month. The quakes are shallow, occurring at depths of less than 4 km (2.5 miles) below sea level, with the largest event reaching M2.7. Over 3 400 earthquakes have been detected beneath Mount Spurr since April 2024.
Ground deformation continues, with the GNSS (GPS) station nearest to the volcano measuring a total outward movement of 6.5 cm (2.6 inches) to date. This suggests a magma intrusion at depths of 3–5 km (2–3 miles) below sea level, approximately 3 to 4 km (2 miles) west of the summit.
According to AVO, multiple scenarios remain possible. The most probable is an explosive eruption similar to those in 1953 and 1992, which lasted several hours and sent ash clouds hundreds of kilometers (miles) downwind, depositing up to 6 mm (0.25 inches) of ash over south-central Alaska. Such an event would likely produce pyroclastic flows, ballistic projectiles, and lahars (mudflows) in surrounding drainages.
A less violent eruption scenario could involve lava flows, lava domes, or small explosive events with limited ash dispersal. Another possibility is that the magma remains trapped underground, as occurred during the 2004–2006 unrest period, leading to a gradual decline in activity.
While less likely, a large explosive eruption exceeding the size of past events is not ruled out. However, historical data and geological records suggest such eruptions are rare.
AVO continues to monitor the volcano using seismic stations, infrasound sensors, GNSS stations, web cameras, satellite imagery, and lightning detection networks. While changes in seismic activity, gas emissions, and ground deformation are expected before an eruption, there is also a possibility that an eruption could occur with minimal warning.
Elevated CO2 and SO2 emissions pose an immediate hazard to anyone near the summit or in low-lying areas downwind of the gas vents. CO2 is colorless and odorless, making it difficult to detect without specialized instruments.
Mount Spurr is part of the Alaska Peninsula Volcanic Arc and features multiple vents, including the Crater Peak vent, which was responsible for the confirmed eruptions of 1953 and 1992. The 1992 eruption produced an ash cloud that rose to 20 km (65 000 feet) a.s.l., affecting air traffic and depositing ash over Anchorage.
Although the summit vent has not erupted in thousands of years, it showed signs of unrest between 2004 and 2006, when increased seismicity and ground uplift melted part of the summit ice cover and triggered debris flows, though no eruption occurred.
References:
1 Mount Spurr – AVO/USGS – March 12, 2025
2 Mount Spurr – GVP – Accessed on March 13, 2025
Rishika holds a Master’s in International Studies from Stella Maris College, Chennai, India, where she earned a gold medal, and an MCA from the University of Mysore, Karnataka, India. Previously, she served as a Research Assistant at the National Institute of Advanced Studies, Indian Institute of Science, Bengaluru, India. During her tenure, she contributed as a Junior Writer for Europe Monitor on the Global Politics website and as an Assistant Editor for The World This Week. Her work has also been published in The Hindu newspaper, showing her expertise in global affairs. Rishika is also a recipient of the Women Empowerment Award at the district level in Haryana, India, in 2022.
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