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Tuesday, 22 July 2014

Mount Cook Rockfall

Hooker Valley rockfall. - Simon Cox / GNS Science
On the evening of Monday 14th July there was a large rockfall from the western slopes of Mount Cook into the Hooker Valley.   Staff from the Department of Conservation and GNS Scientist Simon Cox flew over the area  to make assessments of the  impact. The first photo shows the view towards Mount Cook with the dark shadow of the rockfall splaying out onto the Hooker Glacier on the left.




photo J Spencer / DoC
Approaching the area, the scale of the rockfall starts to become apparent. As well as the debris fan there is a wide expanse of dust that settled on the opposite wall of the valley.











Photo Simon Cox / GNS Science
The devastated area of mountainside that was swept by the avalanche is well over a kilometre across.





Photo Simon Cox / GNS Science


Because of a prominent ridge in the path of the rockfall, the debris divided into two separate lobes as it poured down the mountain. This photo shows the smaller, upper branch and the white ridge (known as Pudding Rock) that obstructed the torrent of rock and ice debris. In the foreground is the dust covered icefall.





Photo Simon Cox / GNS Science


This is a view of the area from higher up, looking down the valley. Simon estimated that roughly 900 000 cubic metres of rock debris are scattered on the valley floor, having travelled  up to 3.9 kilometres and fallen a vertical distance of 1600 metres. On its journey down the mountain, the avalanche scooped up possibly three times as much snow and ice which mixed with the rock material.









Photo Simon Cox / GNS Science
A view upwards towards the low peak of Mount Cook, showing the source area and path of the rock avalanche












Photo: DoC / J Spencer 
Amazingly, the Gardiner Hut just avoided obliteration due to its favourable location on the tip of Pudding Rock. However it was badly damaged.







 



Photo: DoC / J Spencer
The toilet block was crushed and the hut pushed off its foundations. Luckily no-one was inside.












Photo DoC / D Dittmer
Clinging to the mountain amongst a sea of debris. The Gardiner Hut was in the best possible position to (almost) avoid destruction in this rockfall event.






Photo DoC / D Dittmer

Finally here is a view of the headscarp with the 300 metre high x 100 - 150 metre wide grey rockfall scar on the cliff face, the source of all the devastation.




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