Gas emissions, earthquakes, and ground deformations. These are all signs that a volcano is about to erupt, and they are also all signs that have appeared at Mount Spurr, an active volcano in southcentral Alaska, around 80 miles west of Anchorage.
According to the team at the Alaska Volcano Observatory, “significantly elevated” emissions of volcanic gas have been detected at the volcano the tallest in the Aleutian Arc this month, along with elevated earthquake activity and ground deformations, or shifts in the surface of the volcano. According to the team’s statement from March 12, 2025, these signs indicate that an eruption is looming likely to occur within a few weeks or months.
What Is Mount Spurr?
Mount Spurr is a stratovolcano located about 80 miles (130 kilometers) west of Anchorage, Alaska. Standing at 11,070 feet, it is the highest volcano in the Aleutian volcanic arc. Its proximity to major population centers and air traffic routes makes it one of the most hazardous volcanoes in North America.
A History of Powerful Eruptions
- 1953: Mount Spurr’s last confirmed major eruption sent ash plumes into the sky, disrupting air travel.
- 1992: The smaller Crater Peak vent, located just south of the summit, erupted, releasing massive ash clouds that drifted over Anchorage.
- Present: Increased seismic events and gas activity suggest that Mount Spurr may be preparing for another cycle of volcanic activity.
An Explosive Volcano Eruption?
According to the Alaska Volcano Observatory team, the increasing volcanic activity at Mount Spur is likely an indicator of an imminent explosive eruption, about as explosive as the eruptions that occurred at the volcano in 1953 and 1992. Including one or more explosive events, this sort of eruption would create ash clouds and cause ashfall over southcentral Alaska, the latter likely around a fourth-of-an-inch thick. It would also inundate the sides of Mount Spurr with a flow and shower of volcanic rock and ash.
Though it is also possible that the volcano would erupt more or less explosively than it did in 1953 and 1992 or not erupt at all, these scenarios are less likely. The team says that a larger explosive eruption would result in larger ash clouds and thicker ashfall, while a smaller explosive eruption would result in smaller ash clouds and thinner ashfall, with fewer overall impacts. If the volcano doesn’t erupt at all, gas emissions, earthquakes, and ground deformations would slowly decline, disappearing over a few weeks or months without ever escalating into an explosion.
Since the eruptions of 1953 and 1992 have been the only eruptions of Mount Spurr in recent recorded history, it is unlikely that a future eruption would be more explosive. A less explosive burst, or no eruption at all, are thus the most likely of these less-likely scenarios, the team says. As for timing, the signs suggest that the eruption would be sometime soon, with additional elevations in gas emissions, earthquakes, and ground deformations occurring in the lead-up to the blast.
Mount Spurr Reawakens
The volcanic activity at Mount Spurr has been ramping up for months, revealing the intrusions of magma beneath the volcano. Between December and March, these intrusions increased the daily release of sulfur dioxide from the volcano’s summit vent by about 400 metric tons, from around 50 to 450 metric tons a day. The concentrations of carbon dioxide have also increased at Mount Spurr, at the summit vent, and the Crater Peak vent, around 2 miles south of the top of the volcano.
In addition to these elevated gas emissions, the volcanologists at the Alaska Volcano Observatory have also recorded escalations in earthquakes and ground deformations, with over 100 earthquakes having occurred at Mount Spurr each week for at least the last month. Gas vents, also known as fumaroles, are also activating around the volcano’s summit and Crater Peak vents, the latter being the location where the 1953 and the 1992 eruptions occurred.
Though the impending eruption, if it occurs, is likely to look like the eruptions in 1953 and 1992, additional monitoring of the volcano by the Alaska Volcano Observatory team will mitigate the risk of a sudden or surprise blast for the inhabitants of the area around the volcano, which happens to be Alaska’s most populated region.
“We expect additional changes to monitoring data prior to an eruption,” the team reported in their March 12, 2025 statement. “At the current level of unrest, we plan to conduct routine overflights to measure gas emissions, evaluate surface changes, and measure ground surface temperatures.
Recent Signs of Volcanic Activity at Mount Spurr
Scientists at the Alaska Volcano Observatory (AVO) have reported several concerning signs that indicate Mount Spurr may be approaching an eruptive phase.
Seismic Tremors
Over the past few weeks, instruments have detected a significant increase in earthquake swarms beneath the volcano. These tremors suggest magma movement underground, often a precursor to eruption.
Gas Emissions
Sulfur dioxide and carbon dioxide levels have been rising around the volcano. Such gases typically escape when magma nears the surface, signaling that molten rock is pushing upward.
Thermal Hotspots
Satellite imagery has revealed new heat signatures on Mount Spurr’s surface. These thermal anomalies are consistent with magma intrusion beneath the volcano.
Ground Deformation
GPS sensors have detected slight swelling of the volcano, which often occurs when magma accumulates in underground chambers.
How Scientists Monitor Mount Spurr
Monitoring volcanoes like Mount Spurr requires advanced technology and constant vigilance.
Seismic Monitoring
Networks of seismometers record even the smallest earthquakes. A sudden spike in tremors usually indicates magma rising.
Satellite Observations
Satellites track thermal anomalies, ash plumes, and gas emissions in near real-time.
Ground-Based Measurements
Instruments around the volcano measure ground deformation, temperature, and gas composition to provide early warnings.
Public Alerts
The Alaska Volcano Observatory issues color-coded alerts to keep the public and aviation authorities informed. The current status of Mount Spurr has been raised to reflect heightened unrest.
Frequently Asked Questions
Where is Mount Spurr located?
Mount Spurr is located about 80 miles (130 kilometers) west of Anchorage, Alaska. It is the highest volcano in the Aleutian volcanic arc.
When did Mount Spurr last erupt?
The last significant eruption occurred in 1992 at the Crater Peak vent, releasing massive ash plumes that drifted over Anchorage. Before that, the main summit erupted in 1953.
What signs suggest that Mount Spurr may erupt soon?
Scientists have reported increased earthquake swarms, rising gas emissions, ground deformation, and thermal hotspots, all of which indicate magma movement beneath the volcano.
How dangerous could a Mount Spurr eruption be?
An eruption could release large ash plumes, disrupting air travel across the Pacific and covering Anchorage with ash. In a worst-case scenario, it could even affect global climate.
How is Mount Spurr being monitored?
The Alaska Volcano Observatory uses seismometers, satellites, GPS sensors, and gas measurement tools to track activity at Mount Spurr in real time.
Conclusion
The increasing seismic tremors, rising gas emissions, and ground deformation at Alaska’s Mount Spurr highlight the very real possibility of an upcoming eruption. While the scale and timing remain uncertain, the evidence suggests that the volcano is entering a phase of heightened unrest. For residents of Anchorage, nearby communities, and the aviation industry, staying prepared and informed is essential.
As history has shown, even moderate eruptions at Mount Spurr can disrupt air travel, damage infrastructure, and impact public health. On a broader scale, a powerful eruption could have implications that stretch far beyond Alaska, affecting international flight routes and even global climate patterns.
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