A documentary on the 1980 Mount St. Helens eruption in Washington state, that is the origin of the "nuclear winter theory", based on how the eruption pushed large amounts of ash into the upper atmosphere that resulted in a colling of the earth and sever winters throughout most of the 1980's after the eruption. The theory is that nuclear explosions would push so much ash into the upper atmosphere that it would darken the earth and kill all plant life, or at least enough to starve most or all of the world's population. Even a limited exchange between smaller nuclear powers like India and Pakistan could create this effect and kill off the world's population.
On the plus side, this video is filled with beautiful mountain and forest landscapes, presumably filmed mostly from a helicopter. This is the most beautiful disaster area I've ever seen! And has recovered at a remarkable pace. Similar "super-volcano" explosions millions of years ago have released enough toxic chemicals in the air to kill off all animal life on the continent, and others similarly elsewhere in the world. On a smaller scale, Pompei in Italy during Roman times. But this video makes me want to visit there, rather than fear it.
