Exploration of the southernmost part of the globe had been an off-and-on area of interest for centuries prior to the Heroic Age, yet the sheer isolation of the region as well as its inhospitable climate and treacherous seas presented enormous practical difficulties for early maritime technology. Curtailing what is commonly known as the Age of Exploration, British explorer James Cook became one of the first explorers known to have traveled to the region. The discoveries of his second voyage (1772–1775) changed the world map forever. Prior to this expedition it was believed that a large continent known as "Terra Australis" occupied the majority of the Southern Hemisphere. Cook discovered that no such landmass existed, though massive ice floes prevented his reaching Antarctica proper. In the process his expedition became the first recorded voyage to cross the Antarctic Circle. He did hypothesize that, based upon the amount of ice, there must be a landmass from which the ice originated, but was convinced that if it existed this land was too far south to be either habitable or of any economic value. Subsequently, exploration of the southern regions of the world came to a halt.