The pair, both working for the U.S. Fish and Wildlife Service, had been expected to be airlifted off Kasatochi by helicopter late Wednesday, the Anchorage Daily News reported.
The 2-square-mile island about 50 miles west of Adak is uninhabited. Kasatochi is the summit of an underwater volcano that rises to 1,000 feet above sea level. The crater contains a lake.
The Alaska Volcano Observatory issued a yellow alert for planes flying in the area because of the seismic activity.