The magnitude 6.3 earthquake that hit the last February 22 New Zealand not only caused havoc in city of Christchurch but also affected the Tasman Glacier, nearly 200 kilometres to the west of Christchurch.
Ice with the overall mass of 30 million tons broke off from the glacier tongue, a fragment nearly 1.200 meters long and 75 meters broad. Eyewitnesses report that the break-off caused a three meter high wave.
The glacier tongue was already instable and closed for tourists due to heavy rain in the last months. The water from above, in combination with the water of the lake, melted large quantities of ice and destabilized the glacier.
Like many glaciers worldwide also the Tasman Glacier is retreating since 1976, in the free space between the actual glacier and the moraines a ice-contact lake developed. The contact between ice and water accelerates melting and iceberg calving from the glacier.
Ice with the overall mass of 30 million tons broke off from the glacier tongue, a fragment nearly 1.200 meters long and 75 meters broad. Eyewitnesses report that the break-off caused a three meter high wave.
The glacier tongue was already instable and closed for tourists due to heavy rain in the last months. The water from above, in combination with the water of the lake, melted large quantities of ice and destabilized the glacier.
Like many glaciers worldwide also the Tasman Glacier is retreating since 1976, in the free space between the actual glacier and the moraines a ice-contact lake developed. The contact between ice and water accelerates melting and iceberg calving from the glacier.
Fig.1. Tasman Glacier with the Tasman Lake, the icebergs at the southern border of the lake are the remains of the collapse caused by the earthquake February 22 (ASTER-image by NASA, 02 March 2011). The comparison with older images show that mostly a part on the western lakeshore disappeared.
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