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parallaxicality
2012-Jun-25, 09:56 AM
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
2012-Jun-25, 01:49 PM
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
2012-Jun-25, 02:42 PM
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
2012-Jun-25, 06:16 PM
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 (http://en.wikipedia.org/wiki/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
2012-Jun-25, 06:24 PM
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
2012-Jun-25, 06:28 PM
heck with you Eurocentrics. You're Eurasians. Deal with itIt 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
2012-Jun-26, 01:57 AM
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
2012-Jun-26, 02:24 AM
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
2012-Jun-26, 04:09 AM
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
2012-Jun-26, 04:58 AM
... 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
2012-Jun-26, 06:14 AM
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 ('http://en.wikipedia.org/wiki/Zealandia_%28continent%29'). Besides a continent can be on more than one plate. The eastern end of Siberia is on the North American plate.

Gillianren
2012-Jun-26, 08:16 AM
Which ends in Iceland.

Ivan Viehoff
2012-Jun-26, 08:23 AM
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
2012-Jun-26, 08:29 PM
In alphabetical order: Africa, America (N), America (S), Antarctica, Asia, Australia

parallaxicality
2012-Jun-26, 08:51 PM
Judging from this map (http://upload.wikimedia.org/wikipedia/commons/9/93/Elevation.jpg), 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
2012-Jun-27, 02:09 AM

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
2012-Jun-27, 07:27 AM
I would specify continental crust as opposed to oceanic crust.

Ara Pacis
2012-Jun-27, 07:36 AM
I would specify continental crust as opposed to oceanic crust.Circular argument is circular.

HenrikOlsen
2012-Jun-27, 07:55 AM
Circular argument is circular.
... because it's circular.

parallaxicality
2012-Jun-27, 08:12 AM
Iceland and Hawaii are oceanic crust, so they wouldn't count.

Jens
2012-Jun-27, 08:17 AM
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
2012-Jun-27, 08:26 AM
Really? Members of a science board would ask that?

Jens
2012-Jun-27, 08:33 AM
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
2012-Jun-27, 09:13 AM
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
2012-Jun-27, 12:49 PM
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
2012-Jun-27, 02:54 PM
Judging from this map (http://upload.wikimedia.org/wikipedia/commons/9/93/Elevation.jpg), 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 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
2012-Jun-27, 03:40 PM

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
2012-Jun-27, 06:14 PM
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
2012-Jun-27, 06:16 PM
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
2012-Jun-27, 06:38 PM
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.

Ara Pacis
2012-Jun-27, 08:27 PM
I think we should define it in military terms. If an army can march across and easily invade, it's not a continent, if an army can be stopped at the bottleneck by a relatively inferior force or require boats or a temporary floating bridge, then it's a continent. Obviously, Thermopylae is a continental divide. :)

parallaxicality
2012-Jun-28, 06:30 AM
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.

So astronomers shouldn't use pi to calculate light magnitudes, because there's no such thing as a perfect circle?

And anyway, do you not think that dividing stars into "red dwarfs", "blue giants" and "red giants" aids in understanding stellar evolution?

Jens
2012-Jun-28, 07:11 AM
And anyway, do you not think that dividing stars into "red dwarfs", "blue giants" and "red giants" aids in understanding stellar evolution?

I think it's valuable, as you say, for trying to understand stellar evolution. Similarly, debating the difference between hydrogen and helium is interesting for understanding how matter is made.

What I don't understand is, what is the importance of discussing whether Australia is an island or a continent?

WayneFrancis
2012-Jun-28, 07:30 AM
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)

Could go with 14 by the physical major plates that make up the Earth's crust.

parallaxicality
2012-Jun-28, 08:56 AM
I think it's valuable, as you say, for trying to understand stellar evolution. Similarly, debating the difference between hydrogen and helium is interesting for understanding how matter is made.

What I don't understand is, what is the importance of discussing whether Australia is an island or a continent?

The issue isn't whether or not Australia is a continent. What is ultimately at issue is what a continent IS. Obviously the Earth's surface is composed of land and water. But the land is different at different lattitudes, and is separated by water of different depths. At what point do these differences cease being quantitative and become qualitative? That is the question I am asking.

Hornblower
2012-Jun-28, 04:15 PM
The issue isn't whether or not Australia is a continent. What is ultimately at issue is what a continent IS. Obviously the Earth's surface is composed of land and water. But the land is different at different lattitudes, and is separated by water of different depths. At what point do these differences cease being quantitative and become qualitative? That is the question I am asking.

I would say that this is a classification judgment call, perhaps with gray areas around which there can be reasonable differences of opinion. Once again, let's make an analogy with the planets. There is a distinct break in the size distribution between Mercury and Ceres, and before 1930 that made a clean boundary between major and minor planets. Pluto and Eris mess that up and leave us with the current controversy.

What the continental plates have in common is that they are much thicker than the deep ocean plates. That leaves us with size distribution to consider our choice of terminology for thick-crust islands that are smaller than the traditional continents. There is a distinct size break between Australia and Greenland, but that would have been messed up by India and vicinity in ancient times when it was separated from the Asian landmass by open sea.

When we add military considerations in ancient times, I can see how a narrow isthmus such as Panama or the Sinai provided good justification for considering the lands on either side to be distinct continents.

With all of this, and taking Australia as the lower bound on the basis of size, I would say six, looking at the big picture. I can see local cultural grounds in ancient times for looking upon the Bosporus/Dardanelles channel as a distinct Europe/Asia boundary, but farther north I just do not see such a sharp meaningful boundary.

Ara Pacis
2012-Jun-28, 06:30 PM
The issue isn't whether or not Australia is a continent. What is ultimately at issue is what a continent IS. Obviously the Earth's surface is composed of land and water. But the land is different at different lattitudes, and is separated by water of different depths. At what point do these differences cease being quantitative and become qualitative? That is the question I am asking.How do you count eustasy and isostasy?

Jens
2012-Jun-29, 12:14 AM
At what point do these differences cease being quantitative and become qualitative? That is the question I am asking.

So you're asking from a geological perspective? In that case, the question of for example whether North and South America should be considered separately or not because they are divided by a man-made canal becomes silly, since it has not significance geologically, right?

whimsyfree
2012-Jun-29, 06:03 AM
With all of this, and taking Australia as the lower bound on the basis of size, I would say six, looking at the big picture. I can see local cultural grounds in ancient times for looking upon the Bosporus/Dardanelles channel as a distinct Europe/Asia boundary, but farther north I just do not see such a sharp meaningful boundary.

Culturally Europe includes Russia and so reaches the Pacific. If culture is the main criterion you could divide Eurasia into at least four: Europe being conventional Europe plus Russia, East Asia, South Asia, and West Asia. Whether SE Asia belongs with South Asia or East Asia or on its own is debateable. This scheme has the advantage of cutting oversized Asia down to size.

I've noticed reports in the media that imply China is a continent, recently.

profloater
2012-Jun-29, 08:37 AM
taking the longer view there is just one continent temporarily split into wandering factions. Culturally to extend a famous English newspaper headline: "fog in channel continents cut off"

crosscountry
2012-Jun-30, 07:09 PM
So you're asking from a geological perspective? In that case, the question of for example whether North and South America should be considered separately or not because they are divided by a man-made canal becomes silly, since it has not significance geologically, right?

geologically, North and South America are distinct plates and distinct continents only recently connected (in geologic time)

crosscountry
2012-Jun-30, 07:11 PM
I've noticed reports in the media that imply China is a continent, recently.

That's possible with India, but China is firmly locked into Asia.

transreality
2012-Jul-03, 01:49 AM
Asia is a composite of a whole lot of fragments of gondwana that have recoalesced, with india just being one of the latest of these fragments. South america broke from gondwana, but North america assembled from some terranes that were always distinct from gondwana, as did europe, so they have quite different histories to the parts to which they are currently attached (south america and asia respectively).

crosscountry
2012-Jul-05, 04:08 PM
My understanding is that much of west Texas was originally part of Antarctica. Japan is made of volcanoes.

If you want to throw a wrench in the "how many continents" issue, use origin of the crust as a definer.

pumpkinpie
2012-Jul-05, 05:12 PM
What's the history of why the 7 continents (at least as I learned them in the 1980's) were determined? To my elementary school mind, NA, SA, Af, Au, An, made sense. But I always wondered how Europe and Asia were considered separate continents. And why the USSR was part of two. How much was culture an influence?

Gillianren
2012-Jul-05, 07:21 PM
Almost completely, as I've said twice. The idea of continents comes from Ancient Greece, so far as I know, and it was yet another category to put Those People Over There into. Remember, the idea of continents came from people who knew that Europe and Asia are connected. As far as their awareness of their world went, you could walk from one to the other. It would not, in fact, surprise me to learn that the first person to divide Europe from Asia was really looking for yet another way to divide Greece from Persia.

whimsyfree
2012-Jul-05, 11:32 PM
Asia is a composite of a whole lot of fragments of gondwana that have recoalesced

That's wrong. Gondwana was what is now Antarctica, South America, Africa, Madagascar and the Australian continent, as well as the Arabian Peninsula and the Indian subcontinent. Not much of Asia came from Gondwana.