It has only now become the talk of the town, as puzzled holidaymakers and residents questioned its appearance.
Dr Chinn explained yesterday Fog Peak is an "index glacier" and one of some 50 Southern Alps glaciers he and the National Institute of Water and Atmospheric Research (Niwa) monitor annually for snowpack changes.
"[The] rock avalanche fell from the summit ridge of Fog Peak just before September 27 . . . The rock material crossed the small Fog Peak glacier, picking up winter snow on the way.
"It was a dangerous winter for avalanches, with some serious incidents throughout the high country. The combined rock and snow avalanche rode the full distance down to the valley floor.
"Spring snow soon covered the avalanche track and it is only now reappearing as summer melt removes the covering snow layers," Dr Chinn said.
He has been monitoring glaciers and studying climate change for more than 30 years.
In more recent years, he amalgamated his data with information collected byNiwa and he continues to work on contract for the institute.
Dr Chinn said he did not have much else to report on southern glaciers at present.
The glacial data was "a bit vague", but it appeared the glaciers had passed the point of continued growth and were due to start receding, he said.
