In a few centuries, the ten thousand or so humans left on the planet will look back at newspapers and laugh at the great lengths we went to to protect ourselves from terrorism. I say this because we are 40,000 or so years overdue for a supervolcano eruption, which is will be an event of cataclysmic proportions, and we should be hoarding food right now.

According to this article and the experts it cites, Yellowstone sits atop one of these supervolcanoes.

"The impact of a Yellowstone eruption is terrifying to comprehend." says Professor McGuire. "Magma would be flung 50 kilometres into the atmosphere. Within a thousand kilometres virtually all life would be killed by falling ash, lava flows and the sheer explosive force of the eruption. One thousand cubic kilometres of lava would pour out of the volcano, enough to coat the whole of the USA with a layer 5 inches thick. The explosion would be the loudest noise heard by man for 75,000 years."

The long-term effects would be even more devastating. The thousands of cubic kilometres of ash that would shoot into the atmosphere would block out light from the sun, making global temperatures collapse. This is called a nuclear winter. A large percentage of the world's plant life would be killed by the ash and the drop in temperature. The resulting change in the world's climate would devastate the planet, and scientists know that another eruption is due - they just don't know when.

Michael Rampino, a geologist at New York University, quoted in a BBC Horizon documentary on Supervolcanoes [7] three years ago explained: "It's difficult to conceive of an eruption this big. It's really not a question of if it'll go off, it's a question of when, because sooner or later one of these large super eruptions will happen."