THE world’s glaciers have been forced into retreat by global warming, but the Moreno Glacier is still on the march and has now, against all predictions, started to prepare for a rare and spectacular explosion of ice and water.

Its relentless forward creep means that Moreno is now acting as a dam across Lake Argentino in Patagonia, into which it empties after its journey down from the Andes.

In recent weeks the glacier’s advance, an estimated 500 metres in the past year, has seen it span the water of the lake and reach the Magallanes Peninsula and so cut off the Rico and Sur inlets from the main body of Lake Argentino.

Experts say that next the water level in the Rico and Sur inlets, fed by mountain streams, will rise by as much as 26 metres (86ft) until the weight of the water will eventually become too much for the glacier to hold back.

When that point is reached, one of Nature’s most breathtaking displays will start. According to Guillermo Chinni, author of a new book on Patagonia’s icefields and a lifetime observer of the Moreno Glacier, there will be an explosion of ice as the water breaches the ice dam.

“It is a tremendous, powerful moment,” he says. “The ice wall bursts from the pressure of water, which, having forced a breach in the glacier, will then cascade down towards Lake Argentino.”

The event, which experts predict will occur in March or April, is all the more exciting because it had been unexpected. The damming and breaching of the lake occurred 15 times between 1917 and 1988, but as the world’s glaciers started to retreat scientists had believed that Moreno, although one of the very few still advancing, would never again manage to dam Lake Argentino. “Nature has once again returned to surprise us, ” Señor Chinni said.

Moving east down from the Andes, the Moreno Glacier is already one of Argentina’s most popular tourist attractions. It is 25km (15½ miles) in length, more than 4km wide at its head and rises 60 metres above Lake Argentino. The entire city of Buenos Aires could fit on to its surface.

Each day the glacier calves several multistorey icebergs into the lake with a huge ripping noise that echoes off the surrounding mountains, to the thrill of tourists. Local scientists hope that public interest in the glacier’s damming of the lake will help to restart public funding for research on the Moreno, which was cut after Argentina’s economic crisis in 2002.

The local tourist industry is also hoping to benefit from the glacier’s most recent advance. Hoteliers and tour operators hope that visitors coming to try to catch the breaching of the glacier will provide a late fillip at the end of what has already been one of their best ever years.

However, Señor Chinni said that anyone determined to witness the breaching of the glacier will have to be patient.

“Previous occurrences tell us that the breaching will probably occur in March or April,” he said.

“But then again it could take as long as several months. After all, we are dealing with an act of Nature.”

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