Posts tagged “mountains

Does Franz Josef Glacier retreat or advance?

As with all the rest of the glaciated world, New Zealand is also losing ice mass at a rapid rate, with 61% lost since 1850 (Hoelzle et al. 2007), and 11% in the last 30 years (T. Chinn, pers. comm.).

Most of this loss is from the large glaciers calving into pro-glacial lakes, such as the Tasman Glacier. This lake formation is the result of glacier thinning in response to climatic warming in the 20th century. As well as these large dynamic changes in glacier volume, there are smaller annual changes in volume due to changes in the amount of snow accumulation and snow and ice melt. An idea of how much mass is lost or gained each year throughout the Southern Alps is given by measurements of the end-of-summer snowlines since 1977. These measurement indicate that there have been positive mass balances at times during this period balance (Chinn et al. 2008) and the very sensitive and responsive Franz Josef and Fox Glaciers have advanced as a result.

The advance of Ka Roimata o Hine Hukatere Franz Josef Glacier since 1984 has been extraordinary given the global pattern of receeding glaciers during this period. Recent work (more…)

Ice Flow

The ice flow of a glacier is divided into two types, internal deformation and basal sliding. Internal deformation is movement of parts of the glacier relative to itself. Throughout the descent of the glacier, the ice at the sides and bottom side of the glacier are subject to more friction from the valley floor and walls, and therefore forced to move at a slower rate than the ice in the centre of the glacier. As a result (more…)

Glacial Erosion

One of the most striking forms of evidence of glacial erosion is the colour of rivers like the Waiho River in Franz Josef. The melt water of the river gains a characteristic greyish colour, sometimes known as glacier milk. This is the result of the suspension of very fine grains of rock <0.002mm in size. These particles are called glacial flour and are the result of a type of glacial erosion known as abrasion. The abrasion occurs where the glacier slides over bedrock and works much like sandpaper, as rock fragments meet at the boundary of rock and ice they grind and smooth the surface below. If a large rock is trapped, large grooves or glacial striations are engraved into valley walls and bedrock.

Another major type of erosion is known as plucking. When the ice slides over the downstream side of the bedrock, it can freeze loosened rocks from the bottom into itself and rips the rocks out from the valley floor and walls, changing its shape forever.

Magic Glaciers of the New Zealand’s West Coast

The unique environment of Westland National Park is responsible for the formation of the local glaciers. These powerful remnants of an ice age manage to survive warming temperatures due to the very special weather conditions on the West Coast of the South Island. Up to 16 metres of precipitation falls on the tops of the Southern Alps every year, most of it falling as snow. This massive amount of snow (more…)