We seem to have an insatiable appetite for disaster movies, an appetite whetted by the prospect of the disaster in question being something that could affect us directly. There have been several made-for-TV drama documentaries tapping into this - in my opinion this one is the best of them.
Supervolcanoes are occasional but massive phenomena with dramatic implications for the human race: it's not so much a matter of "if" we will encounter one (the last took place 75,000) years ago) but "when". As regards the "where", Yellowstone Park in the USA is a likely candidate, it is now known that the park itself sits in the caldera (volcanic crater) of previous huge eruptions, and another one is due... sometime.
That, then, is the basis for this film. The run-up to the eruption is well-done, and the tension expertly built as the scientific team move from scoffing at the very idea to a fearful realisation of what is happening. The acting is uniformly good, and the team-leader conveys very well the picture of a naturally cautious man so afraid of sparking a panic (and subjected to political pressure) that he is virtually in denial of what is happening.
Minimal liberties have been taken with the science, and while there are the inevitable coincidences and fortunate events that move the plot along, the general air is one of great realism (strengthened by the way the film is shot). It is a tribute to how far the technology has come that a TV programme can now boast special effects that a big-screen movie would have struggled for even a few years ago, and that effects technology is very well used here.
All in all an excellent piece of work, impressive and gripping.