What makes an island a continent?

An island is classified a continent for two main reasons:

1. it is too large to be considered an island.

2. It sits on its own tectonic plate.

Examples are Australia, the world's smallest content, and Greenland, the world's largest island. Geographically, Australia is a continent, not an island. As a landform, it could be considered an island as it is entirely surrounded by water and not joined onto any other land mass. For this reason, it is often referred to as an island continent. However, it is too big to be formally classified as an island.

Another reason why Australia is also considered a continent is because it sits on its own tectonic plate. This is different from Greenland, which uses the same land mass as North America. That is why the geological appearances are much different in Australia from anywhere else. A place like Greenland shares the same geologic attributes as North America.