antarctica

Ask most people to name the world's largest desert and they'll say the Sahara. They're wrong — and the reason why reveals what a desert actually is. A desert is defined by how little water falls from the sky, not by sand or heat. By that definition the single largest desert on Earth is Antarctica: a 14-million-square-kilometre sheet of ice that receives less precipitation than parts of the Sahara. The biggest deserts on Earth are frozen.

Mount Everest's summit reaches 8,848.86 meters above sea level, measured in a joint 2020 China-Nepal survey using GPS and gravity data — 86 centimeters higher than the figure used for most of the 20th century. The floor of Challenger Deep in the Mariana Trench sits 10,935 meters below sea level. The total measured vertical range of Earth's surface is therefore approximately 19,784 meters — about 19.8 kilometers from the lowest ocean floor to the highest mountain peak. Buried under 2.7 kilometers of Antarctic ice, the Denman Glacier trough reaches 3,500 meters below sea level: the deepest point on continental land, and the place where the next large ice loss could have catastrophic consequences.

Antarctica holds about 26.5 million cubic kilometres of ice — enough to raise global sea levels by roughly 58 metres if it all melted. Coastlines would be redrawn, hundreds of cities flooded, and global climate fundamentally restructured.