The eruption of a super volcano "sooner or later" will chill the planet and threaten human civilization, British scientists warned Tuesday.

And now the bad news: There's not much anyone can do about it.

Several volcanoes around the world are capable of gigantic eruptions unlike anything witnessed in recorded history, based on geologic evidence of past events, the scientists said. Such eruptions would dwarf those of Mount St. Helens, Krakatoa, Pinatubo and anything else going back dozens of millennia.

The warning is not new. Geologists in the United States detailed a similar scenario in 2001, when they found evidence suggesting volcanic activity in Yellowstone National Park will eventually lead to a colossal eruption. Half the United States will be covered in ash up to 3 feet (1 meter) deep, according to a study published in the journal Earth and Planetary Science Letters.

Explosions of this magnitude "happen about every 600,000 years at Yellowstone," says Chuck Wicks of the U.S. Geological Survey, who has studied the possibilities in separate work. "And it's been about 620,000 years since the last super explosive eruption there."

Past volcanic catastrophes at Yellowstone and elsewhere remain evident as giant collapsed basins called calderas.

A super eruption is a scaled up version of a typical volcanic outburst, Sparks explained. Each is caused by a rising and growing chamber of hot molten rock known as magma.

"In super eruptions the magma chamber is huge," Sparks said. The eruption is rapid, occurring in a matter of days. "When the magma erupts the overlying rocks collapse into the chamber, which has reduced its pressure due to the eruption. The collapse forms the huge crater."

The eruption pumps dust and chemicals into the atmosphere for years, screening the Sun and cooling the planet. Earth is plunged into a perpetual winter, some models predict, causing plant and animal species disappear forever.

"The whole of a continent might be covered by ash, which might take many years -- possibly decades -- to erode away and for vegetation to recover," Sparks said.

Yellowstone may be winding down geologically, experts say. But they believe it harbors at least one final punch. Globally, there are still plenty of possibilities for super volcano eruptions, even as Earth quiets down over the long haul of its 4.5-billion-year existence.

"The Earth is of course losing energy, but at a very slow rate, and the effects are only really noticeable over billions rather than millions of years," Sparks said.

The drama Supervolcano is broadcast in two parts, on BBC One on Sunday 13 March and Monday 14 March. Both transmissions are at 2100 GMT. Two science documentaries called Supervolcano: The Truth About Yellowstone are broadcast after the drama, on BBC Two. Again, these air on Sunday and Monday but at the later time of 2200 GMT

Could an enormous volcanic eruption have had such influence on the world as a whole, and could the same thing happen tomorrow? Catastrophe makes no predictions, but leaves the reader with a new sense of history, nature, and destiny.