Because of thawing of ice cover Antarctica had decreased in size a little � the sea gulfs covered earlier under ice shelf have appeared, and some parts of land had been separated from the continent by sea passages. Marie Byrd land represents the large island separated by shallow sea passage from Transantarctic mountains, located on very long land area stretching from Antarctic peninsula up to Ross island. The mainland of Antarctica represents some plateau sites with separate mountain tops towering on them (for example, at Queen Maud land). Plateaus are surrounded with lowland areas in which some sea gulfs penetrate.