The call for an environmental protocol to the Antarctic Treaty came after scientists discovered large deposits of natural resources such as Coal, Natural Gas and offshore Oil reserves in the early 1980s. Antarctica is considered to be part of the theoretical super-continent known as Gondwanaland, which separated near the end of the Paleozoic era and consisted of South America, Africa and Australia. And, because it once was completely covered in vegetation, many scientists believe it may hold one of the last supergiant oil fields yet to be discovered. The continental shelf of Antarctica is considered to hold the regions greatest potential for oil exploration projects, and although estimates vary as to the abundance of oil in Antarctica, the Weddell and Ross Sea areas alone are expected to possess 50 billion barrels of oil - an amount roughly equivalent to that of Alaskas estimated reserves. However, Antarcticas extreme conditions make oil field accessibility in many areas economically problematic.