SANTIAGO (REUTERS) - Chilean volcano Calbuco, which erupted without warning on Wednesday, is still puffing out ash and smoke, leading airlines to cancel flights from Argentine capital Buenos Aires, some 1,400km east.
Calbuco, considered one of the most dangerous along Chile's chain of around 500 active volcanoes, erupted twice in 24 hours on Wednesday and Thursday, sending up a spectacular 17km-high cloud and coating nearby towns in a thick layer of grey ash.
Authorities have set up a 20km cordon around Calbuco, which is located in the scenic Los Lagos region, around 1,000km south of capital Santiago. Some houses and schools located close to the volcano had collapsed under the weight of the ash, local radio reported.
The ash also presents a threat to air traffic, as particles in the atmosphere can cause problems for planes.
With winds blowing the ash cloud north-east into neighbouring Argentina, Argentine air traffic was the worst affected by Friday.
Delta Air Lines, Air France and American Airlines suspended flights to the main international airport at Ezeiza, near capital city Buenos Aires.
"They were cancelled as a preventive measure, for fear that after landing they might not be able to take off later," said a spokesman for Argentina's National Civil Aeronautic Administration.
"We do not discount the possibility that other airlines might take the same decision."
In the southern Argentine tourist city of Bariloche, flights were cancelled for a second straight day, some roads were closed and children were kept home from school.
In Chile, the ash cloud had reached as far as port city Valparaiso, near Santiago. Delta and American Airlines cancelled flights to the capital, although Chilean flag-carrier LAN said Thursday it has resumed domestic flights to the south.
However, the ash cloud was unlikely to spread much further under current conditions, said David Rothery, professor of planetary geosciences at Britain's Open University.
"Even a lengthy sustained ash eruption would be very unlikely to produce enough ash to spread across the tropical zone," he said.
It was not in line to be as disruptive as the eruption of Puyehue in 2011, which led to flights being cancelled as far away as Australia, he added.
Most of the mines in top copper exporter Chile are located in the north of the country, far from the volcano. Fears over contamination of salmon farms in the south, however, hit the shares of local producers on Friday.
A relatively small amount of ash was still issuing from the volcano, said national geology service director Rodrigo Alvarez on Friday morning.
"It's not a major situation, but we can't rule out a new eruption in the coming hours," he said.