What is a continent?

Continents

A continent is one of Earth’s seven main divisions of land. The continents are, from largest to smallest: Asia, Africa, North America, South America, Antarctica, Europe, and Australia.

When geographers identify a continent, they usually include all the islands associated with it. Japan, for instance, is part of the continent of Asia. Greenland and all the islands in the Caribbean Sea are usually considered part of North America.

Together, the continents add up to about 148 million square kilometers (57 million square miles) of land. Continents make up most—but not all—of the Earth’s land surface. A very small portion of the total land area is made up of islands that are not considered physical parts of continents. New Zealand, French Polynesia, and the Hawaiian Islands are examples of land areas that are considered micro continents. These areas are usually grouped with culturally similar continents, but are geologically distinct.

The ocean, divided into four major bodies of water, covers almost three-fourths of the Earth. The area of the ocean is more than double the area of all the continents combined. All continents border at least two oceans. Asia, the largest continent, has the longest series of coastlines.

Coastlines, however, do not indicate the actual boundaries of the continents. Continents are defined by their continental shelves. A continental shelf is a gently sloping area that extends outward from the beach far into the ocean. A continental shelf is part of the ocean, but also part of the continent. If continental shelves were included in the total land area, continents would make up more than one-third of the Earth’s surface.

“Continent” has more than just a physical definition. To human geographers, the term is about culture. The continents of Europe and Asia, for example, are actually part of a single, enormous piece of land called Eurasia. But linguistically and ethnically, the areas of Asia and Europe are distinct. The various cultural groups of Europe have more in common with one another than they do with cultural groups in Asia. Because of this, geographers divide Eurasia into Europe and Asia. An imaginary line, running from the northern Ural Mountains in Russia south to the Caspian and Black Seas, separates Europe, to the west, from Asia, to the east.

(taken from: http://education.nationalgeographic.com/encyclopedia/continent/?ar_a=1)