Continents and Oceans

There is an old saying that “the Earth has six continents and seven seas.” In fact, that generalization is not too far off the mark. Earth has six continental landmasses:
Africa, South America, North America, Eurasia (Europe and Asia occupy a single large landmass), Australia,
and Antarctica. As for the seven seas, there are five great oceanic bodies of water and several smaller seas.

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What Makes a Continent a Continent?

According to a 2017 paper published in the Geological Society of America’s journal, GSA Today, “The ‘Glossary of Geology’ defines a continent as ‘one of the Earth’s major landmasses, including both dry land and continental shelves.’ It is generally agreed that continents have all the following attributes: (1) high elevation relative to regions floored by oceanic crust; (2) a broad range of siliceous igneous, metamorphic and sedimentary rocks; (3) thicker crust and lower seismic velocity structure than oceanic crustal regions; and (4) well-defined limits around a large enough area to be considered a continent rather than a microcontinent or continental fragment… To our knowledge, the last point — how ‘major’ a piece of continental crust has to be to be called a continent — is almost never discussed.”

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