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Tags geography , Land Mass

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Old 16th February 2021, 11:44 AM   #41
Carrot Flower King
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There's this thing called plate tectonics. Mebbe the OP has heard of it.

There's this science called geology, which shows that continents/land masses have been in different parts of the Earth's surface at different times in the past.

If only there were means of finding this out...
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Old 16th February 2021, 02:00 PM   #42
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Originally Posted by sphenisc View Post
Centrifugal force. The dense, heavy basaltic rocks of the sea floor are thrown outwards towards the rim, so the lighter rocks of the continental land masses float in towards the centre.
Centrifugal force from the earth's spin? I don't see how heavier rocks are thrown further outwards than the lighter ones? Do the continents float?
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Old 16th February 2021, 02:08 PM   #43
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Originally Posted by casebro View Post
Also don't see why oceans should define continents. Ignore the oceans, and the concept of land mass, and things look different. Continents are each surrounded by other continents. "Landmass" is an artifact of water filling the low spots.
I can't picture this, either, as this would suggest the larger landmasses, such as Eurasia, which includes some of the world's highest points (Everest, Andorra, etc) was just a case of their being higher out of the ocean/sea. Yet the highest continent of all - Antarctica - is in the South. It is also the driest and windiest, so likely just a rocky desert underneath its one-mile thick ice cover. Yet this is where the South Pole lies, directly opposite the North Pole, which has no land mass. The oceans in that region are also particularly rough and deep - hence why a search for the missing aeroplane was such a problem in this region, with much of the deep ocean beds never explored (I imagine upside down deep mountainous crevases).

So I think maybe it is to do with the tilt of the earth on its axis as it spins, with the pull of the moon on the tides causing the southernmost regions to have more water coverage and thus less land mass in view.
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Old 16th February 2021, 02:10 PM   #44
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Originally Posted by Carrot Flower King View Post
There's this thing called plate tectonics. Mebbe the OP has heard of it.

There's this science called geology, which shows that continents/land masses have been in different parts of the Earth's surface at different times in the past.

If only there were means of finding this out...
Are you claiming there are fewer or more plate tectonics in the north than in the south? How do you account for the VOLCANOs in Antarctica?
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Old 16th February 2021, 02:23 PM   #45
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Originally Posted by wobs View Post
A brief history of the land masses by Map Men:
https://www.youtube.com/watch?v=Nlzehe4mta4

And why it occurs.
And where we'll be in 250million years. Maybe.
That's looks intuitively probable, given that the silhouette of South America seems to fit that of the West Coast of Africa like a jigsaw. It is likely there has been continental drift but the prediction of 'what it will look like in 250 million years' is just one person's hypothesis.

It also buys into the idea that if all the land mass once fit together like a jigsaw puzzle then it becomes apparent where the idea of a 'missing continent' comes from [Atlantis] as there appears to be one jigsaw missing in that spot.
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Old 16th February 2021, 02:30 PM   #46
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Originally Posted by Lukraak_Sisser View Post
they are now. I'm not familiar enough with archaeology to know if this always was the case, for all we know it's just coincidence?
IMO coincidence is the wrong word here. The continents must be distributed 1 of 3 ways, balanced, more in the north more in the south. No matter which it was you could ask the same question.
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Old 16th February 2021, 02:35 PM   #47
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Originally Posted by casebro View Post
Related question, and food for CTs: Do you think Global Warming is having an effect on the thickness of the earth's crust?
I'm not sure how it's related but the answer is that global warming is having a very slight impact on the thickness of the earths crust. The oceans are part of the crust and thermal expansion has increased sea levels a little over 10cm so far. This is due to expansion of water already there, not new water flowing in from somewhere else so on average global warming has made the earths crust a little over 7cm thicker.
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Old 16th February 2021, 06:39 PM   #48
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Originally Posted by lomiller View Post
I'm not sure how it's related but the answer is that global warming is having a very slight impact on the thickness of the earths crust. The oceans are part of the crust and thermal expansion has increased sea levels a little over 10cm so far. This is due to expansion of water already there, not new water flowing in from somewhere else so on average global warming has made the earths crust a little over 7cm thicker.
a) so melted glaciers have made only an insignificant contribution to sea rise?

b) I was mostly tongue in cheek, but my idea was that the warmer atmosphere would not absorb as much heat form the crust, so the lower layer of crust might melt into the magma. I don't think most people count water as crust. So if we exclude the thermal expansion of the water, how is the crust these days? You know, the hard layer that holds the oceans up?
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Old 16th February 2021, 06:45 PM   #49
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Ignoring the oceans, the water will run to the low spots no matter where the axis is. Think of a globe with the lumps and bumps and off-balancedeness of Earth. Make it like a top- wrap a string around it and give it a toss. Watch as it vibrates and wobbles and finally settles on one axis. Which MUST* be exactly where we are now.

* Physics, dude.

eta: Most tops are also top heavy, conically in fact. No joke.
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Old 16th February 2021, 06:48 PM   #50
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Perhaps The Black Hole of Calcutta is where the string was inserted?
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Old 16th February 2021, 06:51 PM   #51
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Short answer: Because it is the most stable axis point.

Billions of years for wobbles to settle to here.
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Old 16th February 2021, 08:32 PM   #52
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Originally Posted by Samson View Post
I said smoother as I thought the world not round becaise spinning, so oblate but smooth.
No, the Earth is round. The difference due to the oblateness due to spinning that you refer to is on 3 tenths of 1 percent. That's still round.

But the Earth is not smooth because there are places where the terrain changes abruptly.

There is a meme that says the Earth is smoother than a billiard ball. That meme is wrong. The Earth is rounder than a hypothetical billiard ball that barely meets regulation. But it's not clear that any billiard balls are as out of round as the regulations might allow. It's also certain that the Earth has discontinuities that are less smooth than most billiard balls.
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Old 16th February 2021, 11:06 PM   #53
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Originally Posted by lomiller View Post
IMO coincidence is the wrong word here. The continents must be distributed 1 of 3 ways, balanced, more in the north more in the south. No matter which it was you could ask the same question.
I meant it was coincidence they were more in the north at this moment in time.
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Old 16th February 2021, 11:35 PM   #54
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Originally Posted by casebro View Post
a) so melted glaciers have made only an insignificant contribution to sea rise?
<snip>
That was not what he was saying. Glaciers melting would have an additional contribution to sea-level rise. However, we can disregard melting glaciers as all what they are is water moving from one place on the crust to another with a slight decrease in total volume (liquid water has less volume than ice).

As to the question in the title, my answer is that throughout most of history the majority of the world's land mass is in either the Northern or Southern hemispheres. Some of the time most of the landmass would be in only one hemisphere. It would therefore be most unlikely that humans evolved just when the landmasses were half-way though the move from one hemisphere to the other.
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Old 17th February 2021, 12:04 AM   #55
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Originally Posted by lomiller View Post
I'm not sure how it's related but the answer is that global warming is having a very slight impact on the thickness of the earths crust. The oceans are part of the crust and thermal expansion has increased sea levels a little over 10cm so far. This is due to expansion of water already there, not new water flowing in from somewhere else so on average global warming has made the earths crust a little over 7cm thicker.
Yes sounds right the average ocean depth is 3800 meters, same depth as Titanic and MH370 foundered.
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Old 17th February 2021, 12:05 AM   #56
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Originally Posted by RecoveringYuppy View Post
No, the Earth is round. The difference due to the oblateness due to spinning that you refer to is on 3 tenths of 1 percent. That's still round.

But the Earth is not smooth because there are places where the terrain changes abruptly.

There is a meme that says the Earth is smoother than a billiard ball. That meme is wrong. The Earth is rounder than a hypothetical billiard ball that barely meets regulation.
As I've pointed out in message #36, at the scale of a 57mm billiard ball, Mt Everest would be a 40 micron imperfection.

A regulation pool ball must not have imperfections of more then +/- 0.005 inches, which means 127 microns. That's over 3 times bigger.

So, no, we're not talking about "barely meeting regulation". It's WAY smoother than regulation allows.

So, you know, do the maths before proclaiming which memes are wrong and which aren't.

Originally Posted by RecoveringYuppy View Post
But it's not clear that any billiard balls are as out of round as the regulations might allow.
"It's not clear" isn't much of an argument premise. Either you know something to be true or false, or you can't use it as a premise.

Originally Posted by RecoveringYuppy View Post
It's also certain that the Earth has discontinuities that are less smooth than most billiard balls.
Source?
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Old 17th February 2021, 12:31 AM   #57
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Why is the World's Land Mass mostly in the North?

Saves time, shoe leather.
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Old 17th February 2021, 02:55 AM   #58
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Originally Posted by Vixen View Post
Are you claiming there are fewer or more plate tectonics in the north than in the south? How do you account for the VOLCANOs in Antarctica?
How on earth do you manage to get that from my post? Pretty much all of what is now northern hemisphere has been southern hemisphere at one time or another. Why would there NOT be volcanos in Antarctica?

What I said was that there is a whole load of pre-existing science about the subject. One could go and read many, many geological texts or look at many, many geological websites which contain much information about plate tectonics, movements of the Earth's crust and where the different plates have been over time.

None of this is new or secret, hidden only on vaults open to the initiates on the second Sunday after Lent if you know the handshake and password. It is readily available to any and all.

I do not understand the point of your original question in light of the above.

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Old 17th February 2021, 04:47 AM   #59
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Originally Posted by Vixen View Post
Do the continents float?
Seriously, go read some basic geology first to get an understanding of the structure of the planet.

Last edited by Carrot Flower King; 17th February 2021 at 04:53 AM. Reason: Adding missing letter
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Old 17th February 2021, 04:53 AM   #60
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Originally Posted by Vixen View Post
That's looks intuitively probable, given that the silhouette of South America seems to fit that of the West Coast of Africa like a jigsaw. It is likely there has been continental drift but the prediction of 'what it will look like in 250 million years' is just one person's hypothesis.

It also buys into the idea that if all the land mass once fit together like a jigsaw puzzle then it becomes apparent where the idea of a 'missing continent' comes from [Atlantis] as there appears to be one jigsaw missing in that spot.
I don't even know where to begin with this one...

There is more to the idea of South America fitting against West Africa than just the visuals on a map. Wegener may have started off with that, but he didn't have the data subsequently acquired, which gives much more information.

The "missing continent" and "Atlantis" bit is purest nonsense, given the hundreds of millions of years involved, long before primates evolved and there being no possible way humans could have known that until the recent geological modelling. "Missing" in and of itself is pretty nonsensical anyway.

Really, have you ever looked at some basic geology?
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Old 17th February 2021, 05:01 AM   #61
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Originally Posted by Carrot Flower King View Post
Seriously, go read some basic geology first to get an understanding of the structure of the planet.

Stop trolling. You know perfectly well I was responding to someone else's post.
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Old 17th February 2021, 05:05 AM   #62
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Originally Posted by Carrot Flower King View Post
I don't even know where to begin with this one...

There is more to the idea of South America fitting against West Africa than just the visuals on a map. Wegener may have started off with that, but he didn't have the data subsequently acquired, which gives much more information.

The "missing continent" and "Atlantis" bit is purest nonsense, given the hundreds of millions of years involved, long before primates evolved and there being no possible way humans could have known that until the recent geological modelling. "Missing" in and of itself is pretty nonsensical anyway.

Really, have you ever looked at some basic geology?
I have actually. I note you haven't attempted to answer the OP except to hint at some kind of special expertise in 'geology' and 'tectonic plates' whilst failing to answer the question.
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Old 17th February 2021, 05:18 AM   #63
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But the answer DOES lie in plate tectonics and the movement of those plates...

The plates and the continents which lie upon them have, per the geological record, moved around all over the surface of the planet. If you'd asked this question at another point it would be "Why are the continents all in the southern hemisphere?". And the answer would still be the same: that's the way the tectonic plates have moved and are positioned relative to each other.

Why do you think "now" is different to any other time?

I'm not hinting at some special expertise, just alluding to the basics.
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Old 17th February 2021, 05:21 AM   #64
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Originally Posted by Vixen View Post
Stop trolling. You know perfectly well I was responding to someone else's post.
I know what you were responding to. And you asked if the continents float. Some basic reading about the structure of the Earth would have answered that for you, y'know the basic knowledge of geology you claim to have.

Not trolling in the slightest.
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Old 17th February 2021, 05:26 AM   #65
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To elaborate on #64: how do you think the land masses arrived in their current position other than as a result of tectonic movement? There is nothing special about now. Why do you need to think about anything other than those tectonic shifts, which you claim you know about?
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Old 17th February 2021, 06:10 AM   #66
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Originally Posted by Delvo View Post
No. Antarctica is not an especially big continent. That plus Australia plus most of South America plus a relatively low fraction of Africa does not outweigh the combination of Eurasia, North America, most of Africa, and a fragment of South America. In fact it's about a ratio of 2:1, a wide enough difference to easily see by eye.

North
South

It would still be true that the northern hemisphere has most of the crust's conspicuously thick area and the southern hemisphere has most of its conspicuously thin area.
Thought that occurred to me: Isn't the distribution of land mass also pretty lopsided between the Eastern and Western hemispheres? Most of the land mass is in the Eastern Hemisphere.

There's also a concept of a land hemisphere and a water hemisphere, although it seems to be a bit arbitrary.

https://en.wikipedia.org/wiki/Hemispheres_of_Earth
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Old 17th February 2021, 07:45 AM   #67
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Hmm,,,, Water flows to the low spots. Back to the mountains and trenches on a billiard ball size Earth, the slight surface imperfections shows how slight the planet is off perfection. A very small shift in the center of gravity would change land mass percentages. ("Land mass percentages" really means "water locations")

Lessee, CG moves south 100 meters, southern continents get bigger, Arctic ocean expands hugely, land mass par is achieved? How many meters would it take?

And is that the cause of long term climate changes? The crust is wobbling around the core? So IS the CG at the center of the globe?
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Old 17th February 2021, 09:01 AM   #68
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Originally Posted by HansMustermann View Post
As I've pointed out in message #36, at the scale of a 57mm billiard ball, Mt Everest would be a 40 micron imperfection.
Which is comparable to sandpaper grit that can be felt by your fingers and is not as smooth as a billiard ball:

https://www.grainger.com/know-how/eq...per-grit-chart

Originally Posted by HansMustermann View Post
A regulation pool ball must not have imperfections of more then +/- 0.005 inches, which means 127 microns. That's over 3 times bigger.
No, it doesn't use the word imperfection. That number is presented as a tolerance on the diameter. It's referring to how much the diameter can vary from one ball to another or how much the radius can vary across disparate parts of the ball. 127 micron imperfections would be straying it to medium grades of sandpaper.

ETA: https://ourplnt.com/earth-smooth-bil...#axzz6mhC9GB2Q
ETA: https://en.wikipedia.org/wiki/Sand

ETA: And relevant xkcd "what if" about bowling balls but similar subject: https://what-if.xkcd.com/46/

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Old 17th February 2021, 09:54 AM   #69
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Originally Posted by Vixen View Post
That's looks intuitively probable, given that the silhouette of South America seems to fit that of the West Coast of Africa like a jigsaw. It is likely there has been continental drift but the prediction of 'what it will look like in 250 million years' is just one person's hypothesis.

It also buys into the idea that if all the land mass once fit together like a jigsaw puzzle then it becomes apparent where the idea of a 'missing continent' comes from [Atlantis] as there appears to be one jigsaw missing in that spot.
If you watched the clip, it states that there are a number of models showing where the land masses could end up, and largely depends on how the mantel currents will behave in that time.

Interesting stuff though, and brought to us with more than a little humour.
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Old 17th February 2021, 10:06 AM   #70
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Originally Posted by RecoveringYuppy View Post
Which is comparable to sandpaper grit that can be felt by your fingers and is not as smooth as a billiard ball:

https://www.grainger.com/know-how/eq...per-grit-chart
That doesn't say much, since for example silk cloth has deeper ups and downs relating even to just the diameter of the thread, and still counts as smooth. In fact, some of the finest silk thead you can get is around 60 microns, i.e., a 50% bigger bump than Mt Everest in that analogy, and if you weave it, the result will still feel smooth and shiny and all.

But even for sandpaper, just saying something is sandpaper is misleading. Not all sandpaper is created equal. Just because you can feel coarse sandpaper as being, well, coarse, doesn't mean that VERY FINE sandpaper feels particularly coarse too. Because that's the grade we're talking about there. It's the kind used for making wood rather smooth and shiny.

Third, even about billiards balls, not all are created equal. A brand new and polished polymer one, sure, it will be very smooth, and not have scratches or pits of more than 1 micron, most actually under 0.5 microns. An ivory one, which have been made all through the 20'th century and you can in fact still buy (if you're willing to pay extra) can get dents and cracks that are considerably deeper than the Mariana Trench in that analogy.
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Old 17th February 2021, 10:29 AM   #71
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Originally Posted by Vixen View Post
Centrifugal force from the earth's spin? I don't see how heavier rocks are thrown further outwards than the lighter ones? Do the continents float?
That is a joke about flat earthers, but yes the continents are lighter than the oceans bedrock and do float after a fashion.
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Old 17th February 2021, 11:12 AM   #72
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Originally Posted by casebro View Post
a) so melted glaciers have made only an insignificant contribution to sea rise?
A little less than half of sea level rise over the last 100 years is from melting glaciers. Even now the ~200 - 500 billion tons of ice melts each year in Greenland contribute less level rise than thermal expansion.

We know from paleoclimate data that ice sheets in Greenland and Antarctica can much at MUCH faster rates than they currently do. We also know that the rate at which these ice sheets are melting is accelerating.

Older IPCC climate assessment reports factored in little or no increase in ice sheet melting and assumed that most sea level rise would continue to be from thermal expansion. This has caused them to systematically underestimate sea level rise. The last AR was better, but still likely on the conservative side IMO.
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Old 17th February 2021, 11:35 AM   #73
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Originally Posted by Lukraak_Sisser View Post
I meant it was coincidence they were more in the north at this moment in time.
What's it coincidental with?
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Old 17th February 2021, 11:42 AM   #74
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Originally Posted by lomiller View Post
What's it coincidental with?

The way we draw maps


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Old 17th February 2021, 12:17 PM   #75
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Never mind. Not getting involved.
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Old 17th February 2021, 12:56 PM   #76
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Originally Posted by Vixen View Post
I have actually. I note you haven't attempted to answer the OP except to hint at some kind of special expertise in 'geology' and 'tectonic plates' whilst failing to answer the question.
The answer has been given many times over.

The continental masses are in constant motion via the mechanism of plate tectonics. They are effectively sloshing around, sometimes clumping together, sometimes going their separate ways.

However, it happens very slowly, as humans experience time. What you are looking at today appears to be a static arrangement, but it's actually a single snapshot of an ongoing process.

It is in fact exactly like looking at a still image of Tom Cruise running, and asking why he's always poised on his right leg, with his left leg lifted up and dangling in front of him. If you look at a sequence of images taken at different points in time, the mystery becomes clear: He's running. No single pose is permanent. Each one is an ephemeral state that he passes through as he runs.

Same thing here. The continents are clumped in the north right now, because they were somewhere else before, and this is the state they're passing through on their way to wherever they'll end up next. Which will also be a state they're passing through.

Also, your questions betray a surprising and depressing ignorance of even basic plate tectonics. You might want to read up on that a bit, at least the Wikipedia article, before returning to this thread.
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Old 17th February 2021, 05:39 PM   #77
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Random tangentially related anecdote:

When I was in school - primary school to us but Americans would say elementary school - there was a series of posters on the wall of one of the classrooms which illustrated what the world would look like if it were a different shape. There were "What if the world were a cube?" "What if the world were a torus?" "What if the world were a tetrahedron?", etc. With artist's impressions of what it would look like.

One of these was "What if the world were Wegeneroidal?" This one was the only one with a footnote, saying "(conforming to Wegener's theory of continental drift)" The illustration showed continents with big cracks between them.

And this was as late as the 70s, when plate tectonics had been basically confirmed. I don't know how old they were at the time, but they didn't look particularly old. I thought it was amusing that the idea of continental drift was considered equally as outlandish as the idea that the world was a cube, or a torus.
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Old 17th February 2021, 10:51 PM   #78
Lukraak_Sisser
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Originally Posted by lomiller View Post
What's it coincidental with?
The OP's question
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Old 18th February 2021, 12:05 AM   #79
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Originally Posted by arthwollipot View Post
Random tangentially related anecdote:

When I was in school - primary school to us but Americans would say elementary school - there was a series of posters on the wall of one of the classrooms which illustrated what the world would look like if it were a different shape. There were "What if the world were a cube?" "What if the world were a torus?" "What if the world were a tetrahedron?", etc. With artist's impressions of what it would look like.

One of these was "What if the world were Wegeneroidal?" This one was the only one with a footnote, saying "(conforming to Wegener's theory of continental drift)" The illustration showed continents with big cracks between them.

And this was as late as the 70s, when plate tectonics had been basically confirmed. I don't know how old they were at the time, but they didn't look particularly old. I thought it was amusing that the idea of continental drift was considered equally as outlandish as the idea that the world was a cube, or a torus.
I'va once had the opportunity to read a whole bunch of old 'Scientific American' journals. And it was absolutely fascinating to read about the debate going on in the 50's and slowly seeing acceptance of the underlying mechanism coming about.
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Old 18th February 2021, 12:31 AM   #80
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IIRC it's the opposite on Mars. If there was water there the northern hemisphere would be almost entirely ocean and the southern hemisphere almost entirely land.

Of course tectonic activity has stopped on Mars so that's now its permanent state, rather than one it is just passing through as is the case on Earth.
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