The moraine walls show how much the glacier surface has lowered in the last century. Before about 1912 the glacier surface was higher than the lateral moraine. New Zealand's other large valley glaciers have all been suffering a similar loss of ice.
|Tasman Moraine Wall. Julian Thomson GNS Science|
For more information about fascinating processes of glaciation check out this GNS Science web page.
the height survey of Mount Cook recently, it was interesting to see the state of the terminal lake of the Tasman Glacier. This has been expanding rapidly in recent years. Once the lake became well established, the water could undermine and erode the ice much more quickly.
This video that we made several years ago gives a dramatic illustration of this process seen from a boat at close quarters: