'Massive' Mt Cook rockfall
Climbers in Mt Cook National Park were "extremely lucky" to avoid a massive rockslide on the mountain today.
The rockslide is believed to be the largest in the area since 1991.
A Department of Conservation spokeswoman from the Mt Cook office said the rockslide happened just after 2.30pm today.
"It's quite massive and I think it has left a scar on the mountain. I haven't heard of one this big before; not since the one in December 1991."
Rocks fell more than 600 metres down the mountain, she said.
She said 13 people were staying at the nearby Plateau Hut, but nobody was injured.
"They were at the hut when the slide happened and they were extremely lucky. It came very close to them."
She said DOC workers were surveying the damage.
The climbers had been evacuated, she said.
Rob Randell from scenic flight operator Helicopter Line saw the ''football field-sized'' landslide from the air and ''couldn't believe the scale of it''.
''It's like a huge avalanche but it's a dirty, rocky, icy avalanche. I would say roughly that rocks fell from about 10,000 feet to 8,000 feet.
''It really is massive.''
Randell said the slide happened on the Hochstetter glacier, above the Tasman glacier valley.
''I had just jumped on the flight because there was a spare seat and I think it must have happened a couple of minutes before we got over there but we could still see all the grey dust and debris.''
He said tourists on the chopper did not seem to understand what they were seeing.
''For us, we know how big this is and we're all pretty in awe of it but for these people, they might only be seeing snow and mountains for the first time.''
It was a "blessing" that no one was injured.
"That area is popular with climbers and mountaineers but I would say, by that time in the afternoon, most climbers would have finished for the day."
Helicopter Line often flies climbers into the Plateau Hut and said the slide was "scarily close" to the 33-bunk alpine hut.