Possibly the most viewed glaciers in New Zealand are those on Mt Ruapehu. Everybody who drives, flies or takes a train past this largest of the North Island volcanoes cannot help but have their eye drawn to its ice clad summits. Its quite likely that many of us are unaware that what we are seeing are the last remnants of great ice bodies that have persisted for 50 thousand years.
To help explain the special case of Mt Ruapehu glaciers, Shaun Eaves and Martin Brook have published a comprehensive review of glaciers and glaciation of the North Island in the New Zealand Journal of Geology and Geophysics.
Fourteen glaciers grace the slopes of Mt Ruapehu and represent the last of the North Islands glaciation. In the past glaciers provided extensive cover over Mts Ruapehu and Tongariro, were probably on the slopes of Taranaki and some remote basins in the Tararua Ranges and perhaps on the tops of the Kaimanawa Ranges and a niche or two in the Ruahine Ranges.
The review highlights the unique volcanic location of the Ruapehu glaciers. The glacier’s inter-twining, sometimes literally, with the area’s volcanism provides valuable age markers to assist with glacier extent aging. No other glacierised region of New Zealand has this feature.
For all the great glacier-volcanic interaction, the review has come too late for the Whakapapa Glacier. The review describes how in the 1950s the glacier flowed 1.5 km from the edge of the mountain’s summit plateau down to the slopes of New Zealand’s largest ski field. Since then it has retreated, split into two and is now nothing but a snow patch that, in some summers, leaves nothing to see.
The demise of the Whakapapa glacier appears to be the first of many as the theme of retreat and thinning is common to nearly all the mountain’s glaciers. The review suggests that next few decades are predicted to be the last for most of the remaining 14 North Island glaciers.
It might be wise to take an extra look at the white capped mountain this summer when you next drive/fly/train past. It just may be your last chance before the end of the glacial life of the North Island.