The two polar regions, the Arctic and the Antarctic, are vast, icy expanses located at the Earth’s poles. Despite their visual similarities, Antarctica is classified as a continent, while the Arctic is not. This distinction is rooted entirely in geology: whether the region is a massive, continuous landmass composed of continental rock or a deep ocean basin covered by floating ice.
Antarctica: A Landmass Defined by Geology
Antarctica is the Earth’s fifth-largest continent, covering over 14 million square kilometers. It is defined by a massive, continuous landmass of continental crust, largely concealed beneath the Antarctic Ice Sheet. This solid foundation, or bedrock, is composed of less dense, granitic rock, a characteristic feature of continental landmasses worldwide.
The continent rests almost entirely upon the Antarctic Plate, one of the world’s largest tectonic plates. The sheer weight of the ice sheet, which averages at least 1.6 kilometers in thickness, has depressed the underlying bedrock significantly in some areas, pushing it more than 2.5 kilometers below sea level.
Antarctica is considered the highest continent on Earth due to the thickness of its ice, giving it an average surface elevation of around 2,000 meters above sea level. The presence of this enormous, unified continental crust is the definitive factor in its classification.
The Arctic: An Ocean Defined by Ice
The Arctic is fundamentally an ocean covered by ice, centered on the Arctic Ocean, the smallest and shallowest of the world’s five major oceans. The extensive ice cover that characterizes the region is predominantly sea ice, which is frozen saltwater floating on the surface of the deep ocean water.
The Arctic Ocean basin is surrounded by the continental landmasses of North America, Europe, and Asia. There is no central, unified landmass or massive continental crust structure at the North Pole itself. The ocean floor is composed of oceanic crust, which is thinner and denser than continental crust.
The deep ocean basin is divided into the Eurasian and Amerasian Basins by the underwater Lomonosov Ridge. This ridge and the surrounding continental shelves are not large or continuous enough to form a separate continent. The ice is typically only two to three meters thick, contrasting sharply with the miles-thick ice resting on Antarctic land.
Geographical and Tectonic Requirements for Continental Status
The classification of a continent is based on specific geological and geographical criteria. Geologically, a continent must be a vast area composed primarily of continental crust, which is characterized by its lower density and higher silica content compared to the denser oceanic crust. This less dense material causes the continent to “float” higher on the Earth’s mantle, resulting in a high elevation relative to the deep ocean floor.
Furthermore, a continent is a major landmass with defined boundaries and is often associated with its own large tectonic plate. Antarctica meets all these requirements, possessing a massive, unified block of continental crust that forms a high-standing landmass, and it rests on the distinct Antarctic Plate.
The Arctic fails to meet the fundamental requirement of being a massive, continuous land structure. It is defined as an ocean basin surrounded by the northern edges of other established continents. The Arctic Ocean’s central location is not a landmass but a deep body of water covered by floating sea ice. The land around the Arctic Circle is already accounted for as parts of other continents, underscoring the Arctic’s status as a geographical region centered on an ocean, not a distinct continent.