Franz Josef Glacier

The Franz Josef Glacier and its neighbour Fox Glacier are unique in the world. This is because of their particular topographical and climatic setting. They are both fed from a very large neve field (snowfield) at around 3000m altitude that receives up to 12 metres water equivalent of snowfall a year - an incredible quantity. This vast amount of snow, accumulating over a wide area and turning to ice, is then funnelled into and down steep and narrow valleys as a glacier trunk that moves at around 2m per day. It takes about 40 years for snow from the neve to become ice and travel to the terminus or snout of the Franz Josef Glacier (and about 50 years for the Fox). Because of the lower elevation, the temperatures are much warmer here, and melt rates are about 20 metres of ice thickness per year – the highest known rates for any glaciers on earth.
These dynamics make the Franz Josef a highly sensitive glacier, meaning that it responds rapidly to a change in average temperature or in snow accumulation. For example, it takes about 5 or 6 years for an increase in snow accumulation to cause the terminus to advance. The Franz and Fox have the fastest known valley glacier reaction times in the world.
A period of glacial advance began in about 1983 and lasted until 2008. This phase of advance was at odds with most of the world's glaciers which retreated significantly over the same time. It is explained by the fact that in the New Zealand region, there were periods of cooler temperatures over those years, in spite of the broader global warming trend.

As you walk towards the glacier, notice the exposed, vegetation free walls of the valley. They show where the ice was in 2008, and give you an idea of the scale of the glacier’s recent retreat.
Look out for concentric terminal moraines (ridges of boulders that piled up at the end of the glacier during its retreat), erratic boulders, ice-smoothed bedrock, very coarse (conglomeratic) river sediments, and views of the glacier up the valley. The size of some of the boulders is impressive. Why do you think some of the rocks are rounded and smooth whereas others are very sharply jagged? Beyond the final barrier there is an area of ‘dead ice’ that has been left behind by the retreating glacier. It is being shielded from the sun by a layer of surface moraine and is likely to take many years to fully melt away.