How Many Continents Are There?
Aren't there just seven?
In the United States and other English-speaking countries, it is usually taught that there are seven continents on Earth: Asia, Europe, Africa, Antarctica, North America, South America, and Australia (or Oceania, which includes the Pacific Islands). But the world map isn't so simple. The exact number of continents is actually something of a controversy. The definition of the continents is as much a political issue as it is a geological one, leading to multiple continent models.
Doesn't science have an answer?
Geologists and geographers would say a continent is a large landmass surrounded by water. This includes land area and the continental shelf extending beyond it. A continent is usually distinguished from a large island by plate tectonics, as most continents exist on a single large continental plate. Japan, for example, is not a continent despite how large it is. But, since the majority of it is on Asia's plate, it's considered part of Asia instead of being grouped with the oceanic countries on the same plate as the Philippines or the Pacific. Likewise with Greenland. This seems like a reasonable standard for what defines a continent. But, there are two problems with that approach.
The first is that there are subcontinents, large landmasses on their own tectonic plates that are attached to larger continents. India is a subcontinent, as are the Arabian peninsula and the Isthmus of Panama (and other parts of Central America). The movement of these subcontinents is responsible for a lot of mountain ranges and other geographical features. For example, the movement of India toward China is was creates the Himalayas.
The second is that as lot of people don't actually want to use that model. By that standard, Europe doesn't exist. There is zero geological basis for the existence of Europe, and many specialists consider it part of Eurasia. and yet most people on Earth insist that the Ural Mountains demarcate Europe and Asia into separate continents.
This gets even more strange when the matter of Russia comes up. Russia as a single country is always in two continents. Per tradition, there is European Russia and there is Asian Russia. If we went by tectonic plates, there would be Eurasian Russia and North American Russia; the North American plate crosses the Pacific Ocean at the Bering Strait.
In much of Latin America, conversely, it is common to group the Americas together despite being on different plates, due to a perceived continuity across the New World.
What other continent models are there?
Perhaps the most radical model is the Four Continents model. According to this idea, any large connected landmass is the same continent. That would just leave North and South America as a single continent, Africa and Eurasia as a single continent, Australia, and Antarctica.
There is the Five Continents model which still groups the Americas and Caribbean into a single American continent, while still recognizing Eurasia, Africa, Australia and Antarctica.
?There are two competing Six Continents models, which group the Americas but split Europe and Asia, or vice versa.
There is the Eight Continents model, which includes the recently minted Zealandia around New Zealand on top of the traditional Seven Continents.
Then there is the alternate version of the Seven Continents model, which clumps Eurasia but recognizes Zealandia.
Will we ever decide?
This is all likely to change and develop over time. In fact, continents change all the time, in a physical sense and in an abstract sense. The continents used to be all combined into a supercontinent called Pangaea. Over time, Earth's surface could be unrecognizable. On a geological time scale, the largest continent today could simply no longer exist, or the smallest continents could crash together.