Mount Spurr (18 December 2024) (Aleutian Arc, Alaska, USA)

(video taken by Hannah Dietterich & provided by the Alaska Volcano Observatory / United States Geological Survey)
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Several Aleutian Arc volcanoes periodically threaten cities and towns in the Anchorage area of southern Alaska, USA. The Aleutian Volcanic Arc consists of dozens of volcanoes, all formed by subduction of the Pacific Plate beneath the North American Plate (the area is sometimes referred to as the "Bering Plate"). Mt. Spurr, in the northeastern Aleutian Volcanic Arc, is a 10-20,000 year old andesitic, subduction zone stratovolcano that formed after the collapse of a Late Pleistocene volcano (“ancestral Spurr Volcano”). Spurr Volcano had explosive ash eruptions in 1953 and 1992.
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Caption from the Alaska Volcano Observatory (AVO):

Video collected during an overflight of the summit of Mount Spurr on December 18, 2024. The lake formed within the ice covered summit crater in late spring 2024. Its green color and floating yellow debris are due to the presence of sulfur.

On October 16, 2024, AVO raised the color code and alert level to YELLOW/ADVISORY, stating: "AVO has observed a gradual increase in volcanic unrest over a period of several months at Mount Spurr, located about 120 km (75 miles) west of Anchorage. GNSS receivers have detected sustained upward and outward ground deformation since March 2024. An increase in seismic activity has also been noted since April (avo.alaska.edu/image/view/196122). Other indications of elevated activity include the development of a small lake in the summit crater in early summer of 2024.

The largest magnitude earthquake detected in this current period of unrest is a M2.3 earthquake on October 6th. This increase in activity was described in detail in an Information Statement (avo.alaska.edu/news/hans/DOI-USGS-AVO-2024-10-09T19:43:26...) that AVO released on October 9th. Analysis of seismic data indicates a subtle increase in the rate and size of earthquakes over the past few weeks. Because this is a notable departure from the normal background seismicity of the volcano, AVO is raising the Aviation Color Code to YELLOW and the Volcano Alert Level to ADVISORY. However, there are no indications that an eruption is imminent. Often this type of seismicity and ground deformation will decline without producing an eruption.

AVO continues to closely monitor activity at Mount Spurr for signals that would indicate that the volcano is moving closer to an eruption. Based on previous eruptions, changes from current activity in the earthquakes, ground deformation, summit lake, and fumaroles would be expected if magma began to move closer to the surface. Therefore, it is very likely that if an eruption were to occur it would be preceded by additional signals that would allow advance warning.

Over the following two weeks, there more than 180 small earthquakes at Mount Spurr. Over the week of November 1st, there were also a few episodes of possible volcanic tremor, which might indicate deep fluid movement. No unusual activity or surface changes were observed in satellite data or webcam views. AVO staff visited on October 24th to conduct pre-winter maintenance on Spurr’s monitoring network and noted that the fumaroles (steam/gas vents) in Spurr summit’s crater were steaming.
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Publications on previous Spurr eruptions:
Wilcox (1953) - Preliminary Report of the Eruption of Mount Spurr Volcano, Alaska, July 9, 1953, and the Ashfall in the Anchorage Area. 25 pp.

Keith (1995) - The 1992 eruptions of Crater Peak Vent, Mount Spurr Volcano, Alaska. U.S. Geological Survey Bulletin 2139. 223 pp.

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Taken on: December 26, 2024

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Sets appears in: • Alaska Rocks, Minerals, Fossils, Geology • Mt. Spurr (Aleutian Volcanic Arc, southern Alaska, USA)

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