The névé or snowfield at the head of Franz Josef Glacier is over above sea level and in area. This wide névé, which is over deep, feeds large amounts of compacted snow into a steep and narrow valley which drops quickly to very low altitudes: the glacier descends to above sea level in just . This combination of factors leads to Franz Josef persisting where most temperate-zone glaciers would have already melted, and allows it to share a valley with temperate rain forest.