Aerial footage of the extreme chase between an avalanche and a train

Ultra-wide aerial begins miles above snowy peaks, then plunges into a fast dive toward a train entering a mountain pass. An avalanche breaks loose and pours down behind the train, filling the valley with a moving white wall. Camera skims along the ridgeline parallel to the tracks, then swings into a wide arc that keeps both the train and avalanche visible as the train races toward a tunnel. End with a rapid climb revealing the avalanche swallowing the pass behind the tunnel mouth.