“Film was born of an explosive,” reads an intertitle early in Bill Morrison’s latest and longest film to date, Dawson City: Frozen Time. He is literally referring to the roots of nitrate film stock — gun cotton — but the sentiment lingers on in the notion that film is home amidst the blast wave of human destruction.

The story of the eponymous Northern Canada town is also one of ripple effects; the documentary begins and ends with an incredible tale: in 1978, hundreds of nitrate film reels wer...