That photo (click for large image) is from Wikipedia Commons, and is of said mountain during an actual eruption, in 1990.
Ascending eruption cloud from Redoubt Volcano as viewed to the west from the en:Kenai Peninsula. The mushroom-shaped plume rose from avalanches of hot debris (en:pyroclastic flows) that cascaded down the north flank of the volcano. A smaller, white steam plume rises from the summit crater.
Photograph by R. Clucas, April 21, 1990.
Update: February 2, still ticking:
Overnight "a high-intensity burst of volcanic tremor" occurred for six minutes, reports the Alaska Volcano Observatory. The observatory asserts "there was no eruption associated with this tremor."
Increasingly, though, it's appearing that the volcano will indeed erupt, which is an ominous prospect for those those living in communities directly across the Cook Inlet on the Kenai Peninsula.
Update: Wednesday, from the Alaska Dispatch.