By MICHAEL HANLON

Last updated at 10:01 07 May 2008

Few sights in nature can compare to the sheer magnificence of a volcano erupting in full flow.

But while scenes of molten lava are relatively commonplace, this otherworldly picture of Chaiten Volcano in southern Chile shows a truly spectacular, and devastating, volcanic phenomenon.

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This astonishing picture shows the Chaiten volcano erupting during storms in the middle of the night

As clouds of toxic ash and dust tower into the sky, they ionise the air, generating an explosive electrical storm. Colossal forks of lightning spark around the noxious plume as it spews from the volcano's crater, creating an image of raw, terrifying energy - as if the air itself were ablaze.

Now, the worst-case scenario is the collapse of the volcano accompanied by a "pyroclastic flow" - a devastating super-eruption of scorching dense gas and molten rock that would roll down the mountainside at 100mph or faster, incinerating and flattening all in its wake.

Thankfully, experts think this is unlikely at this stage.

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The Chaiten volcano has triggered earth tremors and spewed ash two miles into the air

Seen from space, Chaiten's ash plume streams across Argentina towards the Atlantic

Locals wear masks to protect themselves from the all-pervasive ash near Futaleuf

The gigantic plume of smoke from the volcano dominates the skyline

Pyroclastic flows are also called nuees ardentes - or "burning clouds" - and are probably the single most destructive weapon in nature's armoury, capable of flattening cities in seconds.

It was such a catastrophe that destroyed the Roman town of Pompeii in AD79.

The 3,300 ft Chaiten Volcano, 800 miles south of the Chilean capital Santiago, is erupting for the first time in thousands of years, sending a plume of ash into the sky that stretches as far as Argentina.

It is also spewing out chunks of lava and hot rock. Authorities have already evacuated around 4,200 people from the town of Chaiten, six miles from the volcano, but 300 civilians and troops remain and are being evacuated now. Rescue is complicated by the fact that southern Chile is fragmented by fjords and access is often difficult.

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The village of Chaiten, next to the volcano, was virtually emptied in a massive evacuation

Winds carried the ash to other towns in the region and across the Andes to Argentina

A local resident cycles through the ash as it settles across the town

The authorities are also evacuating a second town, Futaleufu. Some of Futaleufu's 1,000 or so residents had already crossed into neighbouring Argentina, where some areas have been showered with ash and where authorities last week closed schools and treated some for breathing problems.

The ash is more than six inches (15 cm) thick in places, and has contaminated water supplies.

Chile, which sits right on the Pacific's volcanic "ring of fire", has the world's second most active string of volcanoes behind Indonesia.