Renaming the continents

Which configuration makes the most sense?

Europe and Asia arguing about their identity as Eurasia

How many continents are there? Someone who grew up in North America will say 7.

  1. North America
  2. South America
  3. Europe
  4. Asia
  5. Africa
  6. Australia
  7. Antarctica

Ask a geologist, or someone who grew up elsewhere, and they might say something different.

Which is the best answer to the number of continents? Is it 7? Can it really be lowered to 4? Or are there actually more?

Disclaimer

I’m not a geologist. I’m not actually suggesting people to combine Europe and Asia into one, or to combine the Americas. This article is just me having a little fun.

Defining a continent

The term “continent” is very loosely defined. Most of us, including me, think of a continent as a really big piece of land surrounded by ocean. This perfectly describes some landmasses like Australia and Antarctica.

But then there is Europe, Asia, and Africa. All are identified as distinct continents, but they’re physically connected. Europe and Asia in particular are the biggest offenders, at least Africa is only connected by a narrow bit of land. That’s why some geologists refer to Europe and Asia as Eurasia, and then add Africa to make Afro-Eurasia. North and South America are also like this. Both are physically connected, but North and South America are distinguished. The combined name for these two is just America.

To start, we can try defining a continent like this:

Continent
A big piece of land that is surrounded by oceans, isolated from other large landmasses

By this definition, there are 4 continents on Earth.

  1. Afro-Eurasia
  2. America
  3. Australia
  4. Antarctica

For simplicity, let’s say that Australia is the cutoff size for a continent. With that in mind, this list makes some sense. All landmasses above are isolated from each other by oceans. We can call North/South America subcontinents of America, and Europe/Asia/Africa are subcontinents of Afro-Eurasia. What about an alternative definition?

Defining by plate boundaries

Major plate boundaries on Earth

This is a map of all major plate boundaries on Earth.

Plate tectonics 101 Earth's crust is not one solid layer of rock, it is split into many different plates, or giant chunks. These plates sit on top of a viscous but liquid mantle, which flows as it convects heat. Consequently, the plates on top move with the mantle. That's how the continents move around.

There are two types of plates/crust: continental and oceanic. Fairly self-explanatory. Continental plates are thicker and less dense. Oceanic is the opposite.

We can set a new definition for “continent” based on this map. We’ll still set Australia as the lower bound for required area.

Continent
A landmass that makes up a significant portion of a large plate

Now the number of continents increases.

  1. Africa
  2. North America
  3. South America
  4. Australia
  5. Eurasia
  6. Antarctica

What about the Arabian Peninsula and India? Strictly speaking, they make up a big portion of their respective plates. But they are much smaller than Australia and are part of Eurasia. But then again, India was technically an isolated continent millions of years ago. Then there’s the bit of Eurasia that actually belongs to the North America plate. The plate boundary definition gave worse results than the ocean one.

It’s all arbitrary anyways

From the two definitions above, we can at least say this:

  1. Eurasia should be a thing
  2. Calling America one continent or North/South is ok
  3. Africa seems to be more separate than joined
  4. Australia and Antarctica are easily definable

If Europe and Asia being counted as Eurasia is the only change, then there are 6 continents. If the Americas are joined, then 5. I think these numbers make the most sense personally. I’ll consider Africa a separate continent for now, I think it still needs some time until it properly joins Eurasia.

Defining continents in the future

Beringia land bridge

About 20 000 years ago, Eurasia and America were connected by a land bridge. That land is how people crossed into the Americas thousands of years ago, when a glacial period lowered sea levels.

Picture this world:

This would mean that the only isolated landmass is Antarctica. In other words, 90% of Earth’s land is part of one continent. I think that’s big enough to count as a supercontinent. This hypothetical world might seem imaginary, but it could be real in the future. All you need is two things to happen:

  1. Wait about 30 million years (yes, this isn’t happening)
  2. Wait for an ice age (yes, this also isn’t happening)

The Australian plate is currently moving north. Within 30 million years, it should have collided with Indonesia. Then if an ice age causes glacier growth, it’ll lower sea levels. There is submerged land that can connect Eurasia to Indonesia and Australia, this submerged land was above sea level a few million years ago.

Submerged continent Sunda
Image source, CC BY-SA 4.0

You can imagine if Australia moves north, Sahul will collide with Sunda. If sea levels are low enough, Australia will be connected to Eurasia. In 30 million years, Africa will have moved north as well and collide head-on with Eurasia. At that point, there will be two landmasses on Earth: Antarctica, and not Antarctica. Finally, the definition of a continent will be clear.