Why are all the continents the same shape?

[Jojo]

I was looking at a map of the world today and I noticed that Greenland is HUGE. It appears to be as big as (or bigger than) South America. And almost exactly the same shape - wide at the top and tapering down to a point.

Africa is also this shape, as is India. Is there a reason for this or is it just coincidence?

And what continent is Greenland in? I looked up Greenland in the continents section of my Atlas and it doesn't appear to be in any continent so why isn't it a continent in it's own right? It's certainly big enough.

By the way, to see Greenland's size properly you need to look at a good map. Most atlases just truncate it or cut it in half because it's so far north and mostly unihabitable.

Also most of the continental landmasses seem to be in the Northern hemisphere (apart from Australia and Antartica). Is there a reason for this?

Sorry, was that too many questions for one GQ?

[DrFidelius]

Look up distortions on maps using mercator projection. Greenland really isn't that big, look at a globe sometime.

All continents actually are larger versions of political districts in Ennis, Ireland, but you need a really big map to see it.

[Mike H]

No, Greenland is not as big as South America. The map you were looking at was probably a Mercator projection, which distorts area in the high latitudes (i.e., near the poles). If you noticed, Antartica (if it was shown at all) looked like it was bigger than all the other continents.


As for the shape of continents, its probably due to plate tectonics. At one point, millions of years ago, all of the continents were one big continent, Pangea. The continent "broke apart" along fault lines and started to drift away from each other, riding on plates that floated on the molten lava that is within the Earth's mantle. When these continents broke apart, the contour of one continent would match the countour of another continent. Notice how the countour of eastern South America "fits" the countour of west africa. It's because at one time they were merged together and broke apart.

[peepthis]

"Greenland Thinks Mercator Projection Makes It Look Fat"

[The Ryan]

Greenland is considered to be in North America.

[tomndebb]

Aha! You noticed the triangular shape of several of the landmasses (with the points all aiming toward the South), as well as the fact that most of the landmasses are in the Northern Hemisphere.

This is not a coincidence. As the Earth spins, centrifugal force pulls everything up toward the North of the planet. Once the lands got moving in that direction, inertia kept them going on past the Equator into the North (or top) of the planet. And, speaking of tops, you will notice that most of those triangular continents and large islands look rather like tops. (North America used to look like a top, but the Panama Canal weakened its base and it started to crumple, giving it the drunkenly perched dragon shape that it has, now.) The triangular continents are mimicking the Earth in having the Earth's spin drive most of their mass to the North. Eurasia use to be a wide, flattened top until the Indian subcontinent drove into its base, smushing it out into the irregular pattern it now has. Only the base of the Indian "top" is still visible. Australia got its odd shape when it broke free from Antarctica. Notice how it curves across the bottom? The upper edge of the continent is moving away to the North while the Eastern and Western sides are drooping and collapsing in toward the center in its "wake." It, too, will be triangular in about 3.2 million years.

[tomndebb]

ummm

The person who just handed me my meds says that I have to post a retraction for that last post.

[kniz]

Meds, I thought you had too much to drink. ;)

[MEBuckner]

Haven't you ever heard the expression "for medicinal purposes only"?

[Laughing Lagomorph]

I don't know, you were making sense for a minute there, then you lost it somewhere around the Panama Canal...

[Duck Duck Goose]

Worked for me, too.

Hey, play the Kids NASA "tectonics" game.
http://kids.earth.nasa.gov/archive/pangaea/Pangaea_game.html

[TheLoadedDog]

Australia's evil plan (http://www.satirewire.com/news/jan02/australia.shtml).

[tomndebb]

That was just silly, TheLoadedDog. Everyone knows that Australia was simply pushed up out of the ocean whan God stamped the depression to make the Black Sea. Australia is simply a bit larger because of the extra rocks that got picked up by the motion of the impact through the Earth.

- - -

Jojo, as several posters have pointed out:
Greenland is part of the North American land mass.
It is not that large (although it is considered the largest island). (Even with Greenland, North America is actually smaller than Africa.)
The appearance of Greenland as a continental sized land mass is due to the distortion of of any planar surface (i.e., flat) map attempting to depict the curved surface of the Earth. Each flat map introduces some distortions while attempting to produce one aspect of the curved earth. Compare the following different attempts to represent the globe of the earth on a flat map:
The Mercator Chart (http://baby.indstate.edu/gga/gga_cart/gecart86.htm)
THE LAMBERT CYLINDRICAL EQUIVALENT PROJECTION (http://baby.indstate.edu/gga/gga_cart/gecart83.htm)
Postel's Equidistant Projection (http://baby.indstate.edu/gga/gga_cart/gecar209.htm)
Goode's Homolosine Equal-Area Projection (http://baby.indstate.edu/gga/gga_cart/gecar180.htm)

If you look at the Mercator link, you will see why most Mercator maps are truncated before the North and South poles. If not truncated, the polar regions actually look larger than the whole rest of the world.

There are, indeed, several roughly triangular land masses, but they are simply coincidental. There are also "square" land masses (Iberia, Alaska, etc.) and other shapes. (As I pointed out at the beginning of this post, Australia and the Black Sea have strikingly similar outlines.) It is simply coincidence.

In the same way, we really do not know why most of the continental land masses are currently North of the Equator. It is probably coincidence, again. Back before the current continents floated, using plate tectonics, to their current positions, there were periods when most of the land above sea level was gathered into the supercontinents of Pangaea and Gondwanaland. The speculative Gondwanaland is usually thought to have lay South of the Equator and the later Pangaea is also supposed to have had a substantial mass south of the Equator.

[Shalmanese]

"It started off same as always; coupla fossils saying how our Banjo Patterson was a better poet than Walt Whitman, how Con the Fruiterer is funnier than Seinfeld, only they're Aussies so no one knows about 'em," recalled witness Kevin Porter. "Then this bloke Martin pipes up and says Australia's main problem is that it's stuck in Australia, and everybody says 'Too right!'"

My god, I havent heard about old Con in ages!

[Jojo]

Hmm, ok but I notice poor Greenland gets left out in that NASA game, it's not included in North America.

Never mind Australia, they deserve their enforced isolation for having so many silly animals, it's Greenland I feel sorry for. What have they ever done to deserve this treatment?

[Bob Scene]

Originally posted by Jojo
...It appears to be as big as (or bigger than) South America. And almost exactly the same shape - wide at the top and tapering down to a point.

Africa is also this shape, as is India. Is there a reason for this or is it just coincidence?

...Also most of the continental landmasses seem to be in the Northern hemisphere (apart from Australia and Antartica). Is there a reason for this?



All continents start out as a big blob in the Northern Hemisphere and then taper down to a point. It's called the theory of Continental Drip.

[DrFidelius]

Once all the continental mass is at the bottom of the globe, a polar reversal event occurs to start the process over again. Instead of a Plate Techtonics theory, we have Hourglass Techtonics.

[DrFidelius]

Tectonics, dammit.

I die of embarrassment. My unburied courpse, shunned by my friends and family, breeds disease which is spread to all the world. All die. O, the embarrassment!

[TheeGrumpy]

Originally posted by Jojo
And what continent is Greenland in?

As I patiently explain in this thread (http://boards.straightdope.com/sdmb/showthread.php?threadid=107999), Greenland is part of the vast, though little-known, supercontinent of ATLANTICA!

Which is perhaps a misnomer, since most of Greenland borders the Arctic Ocean.