By Juliet Speedy
Another massive chunk of ice has fallen off the Tasman Glacier in Aoraki Mt Cook.
Glacier watchers estimate it would have weighed about 50 million tonnes before it broke off and crashed into the lake sometime over the weekend.
Before and after photos (which can be seen in the video) show which part of the glacier face has broken off. The calved iceberg is enormous - only 10 percent of it is visible above water.
"The calving that's occurred is way bigger than we ever imagined," says Dennis Callasen, Mt Cook Tourism manager. "It's about 30 to 50 million tonnes."
The iceberg has since broken up. There are at least 20 smaller bergs floating in the Tasman Glacier terminal lake, all at least 50m long, "the largest of which is 300m by 200m by 40m high" according to Mr Callasen.
There were warnings of some spectacular glacial action earlier this month after the ice began slowly rising out of the water, right across its 600m wide terminal face.
Just last year another giant iceberg dubbed 'the taniwha' fell off and crashed into the lake in front of a boat load of startled tourists.
But no one witnessed this most recent convulsion - it could have happened at night and daytime tourist boat rides on the lake have been suspended for the winter.
Glacier guides are now expecting booming business this season for those curious to see the results of this natural wonder.
3 News