Tasman Glacier

At 27 kilometres in length, the Tasman Glacier is New Zealand's longest glacier. It is as much as 4 kilometres wide and 600 metres deep, and lies entirely within the borders of Aoraki/Mount Cook National Park. The glacier covers an area of 101 square kilometres and starts at a height of 3000 metres above sea level. Snowfall during the winter and spring seasons accumulates to 50 metres. After the summer melt, 7 metres remains.

The Tasman flows south from the southern slopes of the Minarets peak, along the eastern flank of Aoraki/Mount Cook, the peak of which is only five km from the glacier. Although its upper reaches are snow-covered, rocks carried by the glacier are exposed by ablation along its course, and the lower glacier is entirely rock-covered. It is almost met near its end by the meltwater of the Murchison Glacier, which approaches from the northeast before turning to flow beside the Tasman Glacier outside the moraine wall.

The waters from both these glaciers pool at the end of the glacier in Lake Tasman, before flowing south to join the outflow from the nearby Hooker and Mueller Glaciers in the wide valley of the Tasman River, whose braided streams flow south into Lake Pukaki. They eventually flow into the Waitaki River and to the Pacific Ocean north of Oamaru.

Left to right, the Mueller, Hooker and Tasman Glaciers in the Southern Alps, showing major retreat in the ~10 years circa 1990 to 2000. Notice the larger terminal lakes, the retreat of the white ice (ice free of moraine cover, high up on the glaciers), and (more subtly) the increase in height of the moraine walls due to ice thinning.

Recent retreat

The glacier has retreated about 180 metres a year on average since the 1990s and the glacier is now in a period of faster retreat where the rate of retreat is calculated to be between 477m and 822m each year. It is estimated that the Tasman Glacier will eventually disappear and the terminal Tasman Lake will reach a maximum size in 10 to 19 years time. In 1973 Tasman Glacier had no terminal lake and by 2008 Tasman Lake was 7 km long, 2 km wide and 245m deep.

Logging requirements

To claim a find on this earthcache you will need to perform the tasks described below and email me with the answers and wait for confirmation prior to logging online. Please don’t post the answers online.

Near the posted coordinates you will find an information panel with the answers to all questions.

1.    What is the main title of this information panel?

2.    What is the area of the glacier?

3.    What is the expected lenght by 2027?

4.    Near the posted coordinates take a photo of the Glacier and Lake Tasman showing your GPS unit. This photo should be uploaded with your online log.