How many continents are there?

[parallaxicality]

I would have liked to make this a poll, but there are too many possible answers.

7 (the standard model, you know, with Europe and everything)

6 (heck with you Eurocentrics. You're Eurasians. Deal with it)

5 (Panama Canal? What Panama Canal? We're all Americans, darn it)

4 (and while you're at it, you can take the Suez Canal too! All hail Afro-Eurasia!)

3: (Antarctica? Take the ice off and it's just a bunch of islands)

2: (Australia? An island with delusions of grandeur)

1: They're all just one continental shelf anyway

Dozens: (Hey, check our geology: it says "continental crust". You wanna put us in with Hawaii? Heck with that)

[Hornblower]

I would have liked to make this a poll, but there are too many possible answers.

7 (the standard model, you know, with Europe and everything)

6 (heck with you Eurocentrics. You're Eurasians. Deal with it)

5 (Panama Canal? What Panama Canal? We're all Americans, darn it)

4 (and while you're at it, you can take the Suez Canal too! All hail Afro-Eurasia!)

3: (Antarctica? Take the ice off and it's just a bunch of islands)

2: (Australia? An island with delusions of grandeur)

1: There all just one continental shelf anyway

Dozens: (Hey, check our geology: it says "continental crust". You wanna put us in with Hawaii? Heck with that)

This depends on how we define a continent, and it makes a pretty good analogy to defining and classifying planets.

Suppose we start on the basis of crustal rock structure, where we have thick plates that have a sharply defined shelf that stops about the 100-fathom curve at see, with much thinner plates under the high seas. In that case I would consolidate the traditional continents into three: Africa/Eurasia/Americas, Australia/New Guinea/Tasmania, and most of Antarctica. Greenland is cleanly separated from the American land mass and traditionally is excluded on the basis of size, as are smaller free-standing islands such as New Zealand. New Guinea is structurally part of Australia, while Sumatra, Java and Borneo are structurally part of southeastern Asia.

When we include the present day ocean in our criteria, the Americas are separated from Eurasia, thus increasing my count to four. The isthmus of Panama has a lot of wilderness which could create cultural justification for considering North and South America as separate continents. The Sinai isthmus is less clear, as people in ancient times could travel between Egypt and Israel with no major physical obstacles. The Panama and Suez Canals are superficial cuts easily spanned by bridges.

As I see it, the Ural range between Europe and Asia is the functional equivalent of the Appalachian range in eastern North America, while the Caucasus range corresponds to Continental Divide in the west. I don't see them as meaningful continental boundaries. The southern borders of Afghanistan, Tajikistan and China are much more formidable, and it would make more sense to consider the Indian subcontinent as a continent in its own right, rather than Europe.

[Scriitor]

3: (Antarctica? Take the ice off and it's just a bunch of islands)

No, it's a large landmass. The ice sheets sit on top of it. And without the weight of all that ice, it would sit considerably higher (something like half a kilometer to 1km higher).

[Ara Pacis]

This depends on how we define a continent, and it makes a pretty good analogy to defining and classifying planets.

Does the landmass move around the center of the planet as a unit? Has it solidified into a solid shape or are there parts that are not firmly attached? Is it itself firmly attached to another, larger landmass? Has it cleared its neighborhood of liquid water? Um, we might try to base a definition solely on the ability for a separate landmass to raise sea water in its periphery to a point above the geoid but that might be too accurate.

If we look at those questions semi-seriously, then NZ is a submerged continent and would not count because a submerged continent is not a continent, of course. The Planet definition doesn't discriminate against ice, so maybe a continental definition should include grounded ice as part of its landmass. India is part of the Eurasian system. The Americas would be Double-Continents, but we don't have a definition of Double-Continents, so I guess neither of them can be a continent then. Now, if only we can get a small minority of people to agree with this definition, we'll be golden.

[Gillianren]

When the continents were defined, the distinction was as much cultural as geographical even then. That's why the ancients knew of three continents even though the three they knew are physically attached to one another to the point that there is the greatest debate about two of them.

[Perikles]

heck with you Eurocentrics. You're Eurasians. Deal with it

It depends on whether you regard continent as a cultural concept or not. You could argue that geologically this is all one land mass, but you can't call a person a Eurasian because this automatically involves cultural dimensions which make no sense. Not to me, anyway.

[Celestial Mechanic]

I prefer to think of the continents being four in number:

1. Old World (Africa, Asia, Europe),
2. New World (North and South America),
3. Australia,
4. Antartica.

[Jens]

Some other interesting questions:

How many seas are there?
How many societies are there?
How many languages are there?
How many words are there in the English language?

[Trebuchet]

How many seas are there? Just one, the world ocean. A number of other bodies called "sea", such as the Caspian, are large lakes.

I'd vote for four continents.

[pzkpfw]

... If we look at those questions semi-seriously, then NZ is a submerged continent ...

Oh! I thought we were on the edge of two plates, and the result of some smooshing, not on a piece of continental plate of our own.

[korjik]

Oh! I thought we were on the edge of two plates, and the result of some smooshing, not on a piece of continental plate of our own.

Not according to this. Besides a continent can be on more than one plate. The eastern end of Siberia is on the North American plate.

[Gillianren]

Which ends in Iceland.

[Ivan Viehoff]

And while you are counting Zealandia as a continent, we might as well add Madagascar and Kerguelen, as two further substantial terraine not part of any other continent. Several more candidates listed here. http://en.wikipedia.org/wiki/Microcontinent

It always amuses me that the westernmost point of Iceland is often described as the westernmost point of Europe, when one is plainly already in America at that point. The concept of continent does not admit a very clean counting.

[grapes]

In alphabetical order: Africa, America (N), America (S), Antarctica, Asia, Australia

[parallaxicality]

Judging from this map, I think there are 12 continents: Greenlandiamericafriceurasia, Sahul, Zealandia, Antarctica, Madagascar, Cuba, Hispaniola, Jamaica, the Mascarene Plateau, Jan Mayen Microcontinent, Rockall Plateau, and Kerguelen Plateau. This is all really interesting.

[whimsyfree]

Judging from this map,

Without a definition of continent I cannot judge how many there are from that map. Your definition of continent seems to be a body of land (not necessarily contiguous) separated from all other land by deep ocean waters and not so divided itself. That definition would probably promote dozens of small Pacific archipelagos to continents.

As others have pointed out the concept is largely cultural. You could as well ask how many countries there are, how many races there are, or how many languages there are.

[parallaxicality]

I would specify continental crust as opposed to oceanic crust.

[Ara Pacis]

I would specify continental crust as opposed to oceanic crust.

Circular argument is circular.

[HenrikOlsen]

Circular argument is circular.

... because it's circular.

[parallaxicality]

Iceland and Hawaii are oceanic crust, so they wouldn't count.

[Jens]

Iceland and Hawaii are oceanic crust, so they wouldn't count.

I'm sort of curious why you spend so much energy on a question like this.

[parallaxicality]

Really? Members of a science board would ask that?

[Jens]

In the same way that I find it completely natural to expend energy thinking about why Titan has an atmosphere like it has, for example, but don't understand the effort astronomers put into defining what a "planet" is. It seems to me that the question you asked is very much a semantic issue.

[parallaxicality]

Because definitions have scientific value. We have to draw lines somewhere. Delineating what in the universe goes were is a powerful philosophical tool, because it allows people to conceive the universe in simple terms. So we have to determine which definitions best reflect the universe as it is presented to us.

[grapes]

Iceland and Hawaii are oceanic crust, so they wouldn't count.

It seems like your approach is geology based, then, and is the distinction between the sial (continental) crust and the sima (oceanic) crust?

Because definitions have scientific value. We have to draw lines somewhere. Delineating what in the universe goes were is a powerful philosophical tool, because it allows people to conceive the universe in simple terms. So we have to determine which definitions best reflect the universe as it is presented to us.

And the categories "continental" and "oceanic" may have been superseded, once you take a geochemistry approach. Silica-aluminum and silica-magnesium are just end-members of a continuum.

The sima (basalt) crust sinks as it cools, the sial crust floats. That produces the highs and lows that we know as continents and oceans. Does it make sense to ask how many oceans there are? Right now we tend to agree that there are four, but the boundaries are vague and arbitrary. Similarly for continents.

The question, how many continents, may be interesting, and bring up scientific issues, but the answer has to be arbitrary.

[crosscountry]

Judging from this map, I think there are 12 continents: Greenlandiamericafriceurasia, Sahul, Zealandia, Antarctica, Madagascar, Cuba, Hispaniola, Jamaica, the Mascarene Plateau, Jan Mayen Microcontinent, Rockall Plateau, and Kerguelen Plateau. This is all really interesting.

I prefer this map

I base my continents on plate tectonics. Individual plates that have large landmasses constitute a continent. The Pacific plate, for example, is not a continent, but Africa is.

[Grashtel]

I prefer this map

I base my continents on plate tectonics. Individual plates that have large landmasses constitute a continent. The Pacific plate, for example, is not a continent, but Africa is.

Which has its own set of odd results such as Siberia being part of North America and Arabia and India being continents in their own right. I think defining continents is like defining species, we can all agree that there are divisions somewhere but deciding exactly where and how many is much harder and more subjective than you would at first think.

[HenrikOlsen]

Really? Members of a science board would ask that?

People on a science board are the first to know that knowing the name of something doesn't mean knowing anything about the thing itself.

Artificial distinctions and classifications are not knowledge.

Whether the world is separated in 1,3 7, 9 or 12545783 continents it's the same world and the number will tell you absolutely nothing about the world, though it will tell you something about the person who picked the definition that led to that number.

[HenrikOlsen]

We have to draw lines somewhere.

No. Just plain no.

Drawing lines is the purview of politicians, not scientists.

Drawing lines is a debating tactic for people with an agenda, not a way to gain knowledge.

[Gillianren]

Which has its own set of odd results such as Siberia being part of North America and Arabia and India being continents in their own right. I think defining continents is like defining species, we can all agree that there are divisions somewhere but deciding exactly where and how many is much harder and more subjective than you would at first think.

I don't think that's a bad assessment of the situation. I would add that it's taking a cultural term and trying to force it to be scientific.