USGS Volcano Notice for Aviation - DOI-USGS-AVO-2025-08-19T21:03:20+00:00

(1) VOLCANO OBSERVATORY NOTICE FOR AVIATION (VONA)
(2) Issued:	(20250820/1807Z)
(3) Volcano:	Spurr (VNUM #313040)
(4) Current Color Code:	GREEN
(5) Previous Color Code:	YELLOW
(6) Source:	Alaska Volcano Observatory
(7) Notice Number:	2025/A510
(8) Volcano Location:	N 61 deg 17 min W 152 deg 15 min
(9) Area:	Cook Inlet-South Central
(10) Summit Elevation:	11070 ft (3374 m)
(11) Volcanic Activity Summary:	Over the past several months, signs of volcanic unrest at Mount Spurr—including small earthquakes, gas emissions, melting ice, and surface changes—have been gradually decreasing. No ground deformation has been detected since March 2025. Taken together, this means that the movement of magma toward the surface, which began in early 2024, has stopped. As a result, the chances of an eruption in the near-term are now considered extremely low. Because of this, the Alaska Volcano Observatory (AVO) is lowering the Aviation Color Code to GREEN and the Volcano Alert Level to NORMAL, indicating that the volcano is currently quiet. Small earthquakes are still occurring more frequently than before the unrest began in February 2024, and volcanic gases are still being released from the summit crater and the Crater Peak vent on the south flank of the volcano. This is normal for volcanoes where magma has moved upward but has not erupted. Minor gas emissions and a slightly higher number of small earthquakes could persist for many months to several years. Although the potential for an eruption occurring in the near-term has passed, the volcano poses hazards for recreators on Mount Spurr. High levels of carbon dioxide gas detected on the rim of Crater Peak suggest that hazardous amounts of this odorless and colorless gas may be present within the crater, but not in local communities.
(12) Volcanic cloud height:	n/a
(13) Other volcanic cloud information:	n/a
(14) Remarks:	Mount Spurr volcano is an ice- and snow-covered stratovolcano located on the west side of Cook Inlet approximately 120 km (75 mi) west of Anchorage. The only known historical eruptions occurred in 1953 and 1992 from the Crater Peak flank vent located 3.5 km (2 mi) south of the summit of Mount Spurr. These eruptions were brief, explosive, and produced columns of ash that rose up to 20 km (65,000 ft) above sea level and deposited several mm of ash in south-central Alaska, including approximately 6 mm (1/4 in) of ash on Anchorage in 1953. The last known eruption from the summit of Mount Spurr was more than 5,000 years ago. Primary hazards during future eruptions include far-traveled ash clouds, ash fall, pyroclastic flows, and lahars or mudflows that could inundate drainages all sides of the volcano, but primarily on the south and east flanks.
(15) Contacts:	Michelle Coombs, Acting Scientist-in-Charge, USGS mcoombs@usgs.gov (907) 786-7497 David Fee, Coordinating Scientist, UAFGI dfee1@alaska.edu (907) 378-5460
(16) Next Notice: