At its centre, the ice can be as much as three kilometres thick, constituting 10 per cent of the world's total fresh-water reserves. The oldest rocks ever dated, 3,700-million years old, were found in Greenland. No commercial mineral deposits have been located. Because of its harsh climate and limited areas of vegetation and topsoil, there is very little agricultural activity. In a few southern areas, there is a scattering of small sheep farms and limited crops of carrots, beets and potatoes.
Wildlife includes polar bear, Arctic wolf, Arctic fox, ermine, lemming, musk ox and caribou.
The principal species of fish, crustacea and mammals in the waters surrounding Greenland are shrimp, whales, seals, halibut, salmon and cod. Shrimp and seal make up 85 per cent of Greenland's exports. Atlantic salmon used to be a significant export commodity, but in recent years the catch is consumed locally. Visitors to Greenland come to understand quickly that the livelihood and the culture of Greenlanders has been dependent on fishing and hunting since time immemorial. The harsh climate and absence of traditional transportation infrastructure suggest that this is unlikely to change, even though there are ongoing attempts to develop mining and tourism industries.