What that explanation doesn't suggest, when you first see a glacier, is it's size. We are talking millions and millions of tonnes of ice, filling a valley:
As the ice moves down the valley, it gouges rock and stone from the sides like a cheese-grater. And, when the ice reaches the warmer lower slopes, the rock is dumped when the ice melts. Hills of rocks are formed as the glacier expands and contracts as the climate slowly changes. Glaciers are one 'badass' weapon in Mother Nature's arsenal of erosion forces.
What makes the Franz Josef glacier special is that it descends down a steep valley to almost sea level; there is a short approach road from the main coast road, a ten minute walk and you come to the massive river bed and a view of the glacier. Half an hour scrambling over the riverbed boulders and you are close to the end of the glacier: 
The other special thing about the Franz Josef Glacier is that it is very fast moving (for a glacier). Wait a while and you can hear and see a chunk of ice falling off the glacier into the river below.
