On November 29, an airplane pilot reported the start of an eruption on Mount Westdahl on Unimak Island in the Aleutian Islands (54.52°N, 164.65°W), according to the Smithsonian Institution's Global Volcanism Network. The pilot sighted an ash plume rising to more than 7 km altitude at 1705 local time ( = UT-11 hours). The main portion of the plume, at about 5 km altitude, extended 80–95 km east-northeast by 0930 the next morning.

About noon, U.S. Coast Guard pilots observed a NE-SW fissure vent 5–8 km long, with at least one active lava flow traveling down the east flank. The area surrounding the vent was ash-covered, and increased runoff and possible mudflows were observed. Vigorous steam and ash emission was visible throughout the day from False Pass (90 km NE), which experienced a very fine dusting of ash. A strong sulfur odor at False Pass lasted into the night, and similar odors were reported by pilots up to several hundred kilometers inland. No ashfall has been reported in Cold Bay (145 km NE).