A large rockslide crashed to the ground in the northern Italian Dolomite mountains early on Friday but no one was hurt.
A "huge mass" of rocks and earth came down from the side of the Cima Una mountain and spread a "massive" cloud of dust through the underlying valley, eye witnesses said.
The 2,600-metre Cima Una is one of the many famous peaks in the area, which is a favourite vacation spot for German Chancellor Angela Merkel.
"It was like something out of the Twin Towers disaster," two German tourists told ANSA in the dust-swathed valley.
Cars coming down the slopes "looked like they'd just been through a snowstorm," witnesses said.
"The great quantity of powder is caused by the high calcium content of Dolomite rock," fire chief Hans Hellweger told ANSA.
Rockslides are fairly common in the Dolomites but this was one of the biggest for years, civil defence sources said.
Bolzano Geological Office Chief Ludwig Noessing said "the slide in Val Fiscalina is exceptionally large compared to similar events that take place quite often in the Dolomites".
The 60,000-cubic-metre slide occurred when a 100-metre tall slab of rock, 30 metres across at the base, came free because of fissures caused by freezing and thawing water.
"We have to carry out a number of tests to establish the exact cause of the event, but we know that Dolomite rock is extremely beautiful but also terribly fragile because it is so porous," Noessing said.
Heavy snow hit the Cima Una last weekend but warmer weather melted it "before another blast of cold hit us this week, turning the water in the cracks to ice".
National Geological Council chief Pietro Antonio di Paola told ANSA events like landslides and rockfalls were becoming more frequent because of climate change.
"It's quite clear there's a direct link between landslips and climate changes. All these natural phenomena are accelerating because of more extreme conditions such as long droughts followed by torrential rain," he said.
"We geologists are working hard to assess and predict these effects".
Local mayor Fritz Egarter said the part of the mountainside "had been threatening to come off for some time".
"Rocks have been falling for months," he said.
No one was caught in the slide but it left a dozen hikers cut off higher up the mountain, rescue services said.
Guides will take them down on the other side of the peak, they said.
