Antarctica, which accounts for a tenth of the world's land surface, is thought to contain immense mineral wealth. A coalfield under the Transantarctic mountains may be the largest on Earth, and iron ore deposits in the continent could meet present world needs for two centuries. Rich oilfields are thought to lie offshore. In all there may be more than 900 major mineral deposits in the continent, and it is thought to be particularly rich in lead, copper and uranium. Extracting minerals would be difficult, expensive -- and uniquely hazardous to the environment of the continent, which has the most fragile ecology in the world. There are 39 Antarctic Treaty nations. From 1981 to 1988, the Antarctic Treaty nations negotiated a convention to regulated mineral prospecting and exploitation. This assumed that mining could be carried out without necessarily doing serious damage to the environment. In 1990, they agreed on an initial ban on mining, perhaps lasting 50 years. Some want to make Antarctica a world park, whilst others say this is outside the realm of practical politics.