Recent earth science developments suggest that how we count our planet’s largest land masses is less clear than we learned in school.
By Matt Kaplan
Oct. 30, 2024
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The world is split up into continents, there are seven in all.
And if you get the gist, we’re going to make a list,
From biggest to small …
Your kids may have come home from school singing this infectious ditty, or another like it. But are there really seven continents?
Anyone with a map can see that Asia and Europe are connected. They are often called Eurasia for that reason. The divide is pretty arbitrary, more culturally than scientifically defined. So, is it fair to say that there are actually only six continents?
That is just the first slippery step on a well-oiled slope. What about North America and Asia?
They are connected by the Bering Sea Shelf, once dry land crossed by humans and flooded only in the geologically recent past. Technically speaking, that makes Asia, North America and Europe all one continent. Does that mean there are only five?
Other experts contend that five, six and seven are wrong and argue in favor of eight continents. There are even those who go as far as to say there are only two.
Hiding within the simplicity of the song, there is an illusion of general agreement about the number of continents.
The dispute arises in part because there are really two types of continents: Those recognized by cultures around the world, and those recognized by geologists. Cultures can define a continent any way they want, while geologists have to use a definition. And geological research in recent years has made defining continental boundaries less simple than it might have once seemed as researchers find evidence of unexpected continental material.
“This triggers a lot of interest because there are significant implications for our understanding of the mechanisms of continent separation, ocean formation and plate tectonics,” said Valentin Rime, a geologist at the University of Fribourg in Switzerland. He added, “But after the excitement comes rigorous checking and debate to make sure the evidence is solid.”
Geologically speaking, to be a continent, a bit of the planet needs to have four things:
- A high elevation relative to the ocean floor.
- A wide range of igneous, metamorphic and sedimentary rocks rich in silica.
- A crust thicker than the surrounding oceanic crust.
- Well-defined limits around a large enough area.
The first three requirements are found in just about every geology textbook. But not so with the fourth. What is “large enough,” or how “well-defined” the limits of a potential continent need to be, are matters that are less often discussed, unless a geologist is studying bits of the planet that are on the cusp of being continental.
“Anything big enough to change the map of the world is important,” said Nick Mortimer, a geologist with the New Zealand government-owned GNS Science research institute. “Labeling and identifying part of the Earth as a continent, even a small, thin and submerged one, is more informative than just leaving a map blank.”
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Forwarded by Shoeb Amin
