Earth’s surface is overwhelmingly dominated by water. The total surface area of our globe is approximately 510 million square kilometers, and the terrestrial surface accounts for less than one-third of that space. This land-to-water relationship defines Earth as an ocean-centric world, with the vast seas shaping global climate and geography.
The Planetary Land-Water Ratio
The surface of Earth is covered by water to an extent of about 71%, leaving the remaining 29% as land area. This ratio translates to roughly 361 million square kilometers of ocean and 149 million square kilometers of land. The oceans contain about 96.5% of all the water on Earth.
The three-to-seven ratio of land to water is a fundamental measurement in planetary geography. The remaining land area supports global ecosystems, and its distribution has profound effects on human civilization.
Defining the Global Landmass
The 29% figure representing the global landmass includes all continents and the thousands of islands scattered across the oceans. Landmasses are defined as the continuous continental crust that extends above the average sea level. This total area is primarily composed of the seven continents.
For cartographic and geological calculations, inland bodies of water such as major lakes and rivers are generally included within a country or continent’s total area. However, they are often subtracted when calculating the dry land area for global ratios to accurately reflect the solid terrestrial surface. The land area also includes the continental shelves before the steep drop-off to the deep ocean floor.
The Imbalance of Land Distribution
The landmass is not spread evenly across the planet, but is clustered almost entirely in one half of the globe. The Northern Hemisphere is frequently called the “land hemisphere” because it contains the vast majority of the world’s land area. Approximately 68% of the planet’s total land is located north of the Equator.
This leaves the Southern Hemisphere, often referred to as the “water hemisphere,” with only about 32% of the global landmass. The Northern Hemisphere includes all of North America and Europe, most of Asia and Africa, and a small part of South America. The Southern Hemisphere is dominated by the Pacific, Atlantic, and Indian Oceans, with land concentrated in Antarctica, Australia, and the larger portion of South America. This geographical asymmetry is a result of the long-term movement and collision of tectonic plates.