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.
Wasting Away
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.