An Associated Press story carried by both the LA Times and the New York times reported that a huge rockslide on Mt. Sanford on April 11, 1981, had been previously mistaken for a volcanic eruption. The text of the story (Associated Press, 1981) is as follows: "A huge landslide on Mount Sanford was mistaken for a volcanic eruption by nearby residents and airline pilots passing overhead yesterday, a University of Alaska scientist says. The slide on the mountain's sheer south face exposed layers of old, loose ash that strong updrafts pushed into a huge plume-shaped cloud, Carl Benson, a member of the university's Geophysical Institute, said after flying over the 16,237-foot peak yesterday. The landslide occurred in a sparsely populated area, and there were no reports of injury or damage."

From Neal and others (1996): "Ground observers in Glennallen reported unusual white cloud formations over Mount Sanford on April 5 and 6, 1993. Another report on April 8, 1993, indicated that the mountain 'was steaming' from low on the east or south side (there were conflicting reports) and the resultant cloud was boiling up the flank to an estimated 5,000 ft (1,524 m) over the top of the peak. This level of apparent activity was more than this observer had noted in 21 years of viewing the volcano. Given the history of rock and ice falls from the shear south flank of the mountain and the fact that the phenomenon was short lived, AVO concluded that the observations were probably related to a large avalanche(s) or to unusual orographically induced weather clouds. No mention of the event was made in the AVO weekly update."

From Neal and others (1995): "On September 30, [1994], the National Weather Service (NWS) contacted AVO with a pilot report of a steam plume over Mount Sanford. AVO contacted the local flight service station in Gulkana and discussed the observation. Given the clear weather conditions at the time, the transience of the plume, and the history of large gravity slides at Mount Sanford, it was concluded that the observation was probably related to a large avalanche. No mention of this event was made in the AVO weekly update on volcanic activity in Alaska."

From McGimsey and Wallace (1999): "A Copper Center resident reported a large steam cloud rising from the southwest face of Mt. Sanford on September 30, 1997. The cloud persisted throughout the afternoon before dissipating. Based on previous similar activity, AVO staff concluded that the cloud resulted from avalanching or debris fall from the southwest face."

From Neal and others (2014): "On March 23, a consulting geologist working in the area reported seeing a 'good size plume' from Sanford on 2 night. A number of Copper River Valley residents shared photographs of Sanford from March 15 when a dramatic looking plume emated from the southern flank and summit of the volcano.
"A similar cloud was reported on October 20 by Pete Dalton, District Ranger for the National Park Service, stationed at the Gulkana Airport. According to Pete Dalton, the plume rose about 2000 to 3000 ft above the summit. AVO received multiple calls regarding the October 20 plume, which appeared to originate from several points on the near-vertical, rocky southern face of the volcano. A towering vapor cloud emanating from the steep rocky face of this volcano has been reported before (McGimsey and others, 1999) and may be related to rock and ice-fall activity, solar warming of the rock and ice face, or a combination of processes. No features related to volcanic heat sources have been documented on Mount Sanford; however, no comprehensive thermal survey has been done."