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.
So, what, exactly, should be expected from the volcano if it does, indeed, erupt?
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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.
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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.”
Read More: What Causes Volcanic Eruptions: Can We Predict Them?
Article Sources
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Sam Walters is a journalist covering archaeology, paleontology, ecology, and evolution for Discover, along with an assortment of other topics. Before joining the Discover team as an assistant editor in 2022, Sam studied journalism at Northwestern University in Evanston, Illinois.
