What's the difference between an island and a continent?
Photo: killthebird
The answer depends on who you talk to.
A geographer – someone who studies Earth’s surface, climate, countries, peoples, and so on – might say that continents are big and islands are small. For example, Greenland, the largest island, is only about a third as big as Australia.
On the other hand, a geologist – someone who studies the physics of Earth as a planet – might say that density accounts for the difference between continents and islands. Continents are made up of low-density rock, so they float high on Earth’s molten mantle like big rafts. Ocean crust is denser, so it floats low on the mantle. Most islands are really extensions of the ocean floor – undersea volcanoes pump out dense lava that cools into ocean floor crust and sometimes piles up to poke above sea level. Greenland is ancient continental crust, but it isn’t big enough to fit the geographer’s definition of a continent. So geologists compromise by calling it a microcontinent.
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