Welcome to Aoraki/Mt Cook National Park. Admission is free and the information panels used in this EarthCache are available from 8:30 am to 6:00 pm daily. Many information panels are available; this EarthCache focuses on glaciers and their influence.
Glaciers are formed from snowfall that accumulates over the permanent snowline. About a quarter of the Mount Cook region is above 2000 meters, the average altitude of the permanent snowline at this latitude. Westerly winds must rise up to 4000 meters to cross the Southern Alps here, so that much of the precipitation the winds bring is in the form of snow.
Today, the Tasman Glacier is the largest and longest in New Zealand. Covering approximately 100 square kilometers (including the lake), the Tasman glacier descends from peaks up to 3000 meters high down 28 kilometers to the terminal moraines at 750 meters above sea level. There are about 180 seperate glaciers, large and small in Aoraki/Mt Cook National Park. The glaciers formed during the ice age about 2 million years ago and continously change size. The furthest extent of the Tasman glacier almost reached modern Twizel. It was 85 kilometers long, up to 13 kms across and a 1000 meters deep.
Shaping the Landscape
All of Aoraki/Mount Cook has been shaped by the work of the glaciers over many millenia. Locate the title information panels and answer the following questions:
(1)What happens to the shape of the river valley before, during and after glaciation?
(2)What happens to the ridges and peaks during glaciation?
The Glaciers and Global Warming
As can be expected, an increase in temperature would affect the glaciers. Over the past 100 years there as been an increase in 0.6 degrees celcius in New Zealand resulting in down-wasting of the glaciers. The effects can be seen in the pictures of the Ball glacier over time.
(3) Please provide the two annual elements that result in the advance or recession of the glacier.
Excavation and Cartage
As the glacier moves, it plucks and scrapes gravel and boulders from bedrock. It constantly excavates, shapes and polishes the floor and side of the valley. On its surface the glacier carries the debris of rockfall from the mountainsides, as well as dirt and dust blown in the wind, even dust from storms and fires in Australia. The glacier carries all this till like a conveyor belt and tips it off as moraine.
(4)Name three types of moraine shown on the panel.
As the glaciers flows lower down the valley, melting increases. Meltwater streams run along the surface and tumble down crevasses or sinkholes and into an underground network of drainage channels and caves. They eventually emerge in the terminal region of the glacier as tributaries to the main fast-flowing river which runs grey.
(5) Why is the water this color?
If you haven't done so already, please make sure to notice this color during your travels to lake Pukaki, lake Tekapo or along the Hooker Valley trail.
To log this EarthCache, please send the answers to the five questions to the email in the profile. Optional: Please also post a picture of yourself and/or your GPSr with the glaciers in the background.