Officially, Earth has seven continents.
The term continent is used to differentiate between the various large areas of the earth into which all the land surface of Earth is divided. This also means the shape and borders of the continents are ultimately defined not by conventions, but in the first place by the level of the surrounding water.
More than two-thirds of the Earth’s surface is covered by water. Two-thirds of the continental landmass is located in the Northern Hemisphere (the upper half of the globe, north of the equator). Islands are frequently grouped with a neighbouring continent to divide all the world’s land into geopolitical regions. Under this scheme, most of the island countries and territories in the Pacific Ocean are grouped together with the continent of Australia to form a geopolitical region called Oceania. For the purposes of this website, we have added Oceania as a separate continent.
There is great variation in the sizes of continents; Asia is more than five times as large as Australia. The largest island in the world, Greenland, is only about one-fourth the size of Australia. The continents differ sharply in their degree of compactness. Africa has the most regular coastline and, consequently, the lowest ratio of coastline to total area. Europe is the most irregular and indented and has by far the highest ratio of coastline to total area.
More than two-thirds of the Earth’s land surface lies north of the Equator, and all the continents except Antarctica are wedge-shaped, wider in the north than they are in the south.
Geological and seismological evidence accumulated in the 20th century indicates that the continental platforms do “float” on a crust of heavier material that forms a layer completely enveloping the Earth. Each continent has one of the so-called shield areas that formed 2 billion to 4 billion years ago and is the core of the continent to which the remainder (most of the continent) has been added. Even the rocks of the extremely old shield areas are older in the centre and younger toward the margins, indicating that this process of accumulation started early.