Antarctica is a unique continent, defined by the massive, permanent ice sheet that covers nearly its entire surface. This vast covering makes defining the continent’s physical dimensions ambiguous. Its size depends on whether the measurement includes the ice, the floating ice shelves, or only the solid rock beneath. Understanding the true extent of the landmass requires distinguishing between the continent’s icy surface area and the solid bedrock that forms the planet’s southernmost land.
The Total Area of the Continent
The figure most commonly cited for Antarctica’s size is approximately 14.2 million square kilometers. This measurement includes the permanent ice cover and the fringing ice shelves that float on the ocean. This immense area makes it the fifth-largest continent, significantly larger than Europe and nearly double the size of Australia. The ice sheet covers about 98% of the landmass, giving Antarctica the highest average elevation of any continent, reaching an average of 2,200 meters.
The Extent of the Bedrock Landmass
The solid landmass of the Antarctic continent is significantly smaller than its ice-covered counterpart. The actual bedrock landmass, excluding the floating ice shelves and islands, measures approximately 12.3 million square kilometers. This figure represents the true geological size of the continent, comparable in size to China and India combined. The difference between the surface area and the bedrock area is accounted for by the sheer volume of the overlying ice. The Antarctic Ice Sheet holds about 27 million cubic kilometers of ice, which, if melted, would raise global sea levels by about 58 meters.
Subglacial Topography of East and West Antarctica
The bedrock beneath the ice is far from a uniform, flat surface, presenting a complex topography that influences the ice sheet’s stability and flow. The Transantarctic Mountains divide the continent into two distinct geological provinces: the larger East Antarctica and the smaller West Antarctica. East Antarctica is an ancient, stable craton where the bedrock is primarily above sea level. This gives it a higher foundation for its massive ice sheet, which is the thickest and most voluminous in the region.
In contrast, West Antarctica is a collection of smaller land features and islands separated by deep marine basins. Much of the bedrock here lies hundreds or even thousands of meters below sea level. This unique geography means that if the ice were removed, West Antarctica would largely become an archipelago. This sub-sea-level grounding makes the West Antarctic Ice Sheet vulnerable to warming ocean currents, as the ice is directly in contact with seawater. The immense weight of the ice sheet has also caused isostatic depression, pushing the continental crust down significantly below sea level.
How Scientists Map the Land Beneath the Ice
Revealing the hidden subglacial landscape requires specialized scientific techniques, since direct observation of the bedrock is impossible across most of the continent. The primary method used to map the bedrock is ice-penetrating radar, also known as radio-echo sounding. Instruments mounted on aircraft transmit radar pulses that travel through the ice and reflect off the solid rock boundary below. This allows scientists to calculate the precise thickness of the ice and the elevation of the bedrock, creating detailed digital elevation models of the subglacial terrain.
These radar surveys are supplemented by gravimetry, which measures minute variations in the Earth’s gravitational pull across the continent. Denser rock exerts a stronger pull than less dense ice, allowing scientists to infer the mass and shape of the land beneath the ice, particularly where radar data is sparse. Major international projects, such as Bedmap and BedMachine, compile decades of data from various sources, including satellite imagery and seismic surveys. These detailed maps are fundamental tools for modeling how the ice sheet will behave in the future and its potential contribution to global sea level rise.