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Relative
2014-Jan-18, 04:28 PM
Plate tectonics is undoubted. But the conclusion that once there was a single continent ("Pangaea") seems doubtful to me. Continents aren't "floating" on the planet's water, so that their movements retroactive lead to one single piece.
1. For the early stage of the planet the question in the Pangaea theory would be, why was there such a large "hill" at a single place?, and wouldn't this have caused a serious wobbling?
2. If the land mass was one piece located at some point, then teared into parts which sheered of from one another, shoudn't there be a significant "opposite" point, where this movement converges?
3. If "Pangea" has broken into several parts somewhere in its middle (i.e. the highest points of it), where are these steep coasts along the shore lines of the Atlantic Ocean's west and east coasts?
Couldn't it be that the earth's crust just had cooled down at some point differently from the layer (or hot material) just below the crust, causing it to crush at random points? This could have happened anywhere causing the random parts to move away from another without the need of a "super continent".

korjik
2014-Jan-18, 04:51 PM
Plate tectonics is undoubted. But the conclusion that once there was a single continent ("Pangaea") seems doubtful to me. Continents aren't "floating" on the planet's water, so that their movements retroactive lead to one single piece.
1. For the early stage of the planet the question in the Pangaea theory would be, why was there such a large "hill" at a single place?, and wouldn't this have caused a serious wobbling?

Total mass of the continents is very small compared to the Earth, so the serious wobbling is still pretty minor. It would just change the frequency of the Milankovitch cycle.


2. If the land mass was one piece located at some point, then teared into parts which sheered of from one another, shoudn't there be a significant "opposite" point, where this movement converges?

This assumes that the continents dont change direction. The seamounts from the Hawaiian hotspot show that the jostling of the continents cause their relative motions to change. Also, they do tend to reconverge.


3. If "Pangea" has broken into several parts somewhere in its middle (i.e. the highest points of it), where are these steep coasts along the shore lines of the Atlantic Ocean's west and east coasts?

Tens of miles off shore. It is called the continental shelf


Couldn't it be that the earth's crust just had cooled down at some point differently from the layer (or hot material) just below the crust, causing it to crush at random points? This could have happened anywhere causing the random parts to move away from another without the need of a "super continent".

That isnt why the supercontinent idea came up in the first place. There are lots of bits of data that lead to the conclusion, like identical species fossils on widely separated continents and that some shorelines go together like jigsaw puzzles.

Relative
2014-Jan-18, 05:06 PM
There are lots of bits of data that lead to the conclusion, like identical species fossils on widely separated continents and that some shorelines go together like jigsaw puzzles.

Which neither is a proof for Pangaea nor an argument against a random break of the crust without an existing single continent...

grapes
2014-Jan-18, 05:20 PM
Plate tectonics is undoubted. But the conclusion that once there was a single continent ("Pangaea") seems doubtful to me. Continents aren't "floating" on the planet's water, so that their movements retroactive lead to one single piece.
1. For the early stage of the planet the question in the Pangaea theory would be, why was there such a large "hill" at a single place?, and wouldn't this have caused a serious wobbling?

There is still such a hill today, and no it does not create serious wobbling. The material of the earth readjusts itself fairly quickly, in response to such wobbling, on the order of hundreds of years. Having such hills does not necessarily mean there will be a wobble--it is possible to offset such hills with material in a configuration that we would not recognize as a hill.


2. If the land mass was one piece located at some point, then teared into parts which sheered of from one another, shoudn't there be a significant "opposite" point, where this movement converges?

There can be, and apparently there have been. Look for "supercontinent supercycle"


3. If "Pangea" has broken into several parts somewhere in its middle (i.e. the highest points of it), where are these steep coasts along the shore lines of the Atlantic Ocean's west and east coasts?

As korjik said, they are there, the edges of the continental shelf.


Couldn't it be that the earth's crust just had cooled down at some point differently from the layer (or hot material) just below the crust, causing it to crush at random points? This could have happened anywhere causing the random parts to move away from another without the need of a "super continent".
Kinda like drying up like a raisin or prune. Yes that was a common theory, but it doesn't explain a lot of the data, whereas plate tectonics does. How, for instance, to explain the continents re-colliding.

Swift
2014-Jan-18, 05:52 PM
Which neither is a proof for Pangaea nor an argument against a random break of the crust without an existing single continent...
Relative,

Be careful. Q&A is for asking questions about mainstream science, and for getting the mainstream answers. You can ask about the evidence of Pangaea, you can even ask follow-up questions to the answers you are given.

But if you cross over the line into advocating non-mainstream ideas (such as Pangaea doesn't exist), you will be infracted and this thread will be moved to Against The Mainstream (ATM)

Relative
2014-Jan-18, 05:59 PM
There is still such a hill today, and no it does not create serious wobbling. The material of the earth readjusts itself fairly quickly, in response to such wobbling, on the order of hundreds of years.

Ok, I know our earth is rather a potatoe but a perfect sphere and that even a potatoe has its balance.
You are talking about such a hill today, which one do you mean exactly? Pangaea is expected to be the one an only "hill" of that time. I would like to visit that.


As korjik said, they are there, the edges of the continental shelf.
Again, nothing against a "random crust break"


Kinda like drying up like a raisin or prune. Yes that was a common theory, but it doesn't explain a lot of the data, whereas plate tectonics does. How, for instance, to explain the continents re-colliding.

Ehm, continents re-colliding? Is this pro or against Pangaea or a random break?

grapes
2014-Jan-18, 06:19 PM
Ok, I know our earth is rather a potatoe but a perfect sphere and that even a potatoe has its balance.

Closer to a billiard ball than a potato.


You are talking about such a hill today, which one do you mean exactly? Pangaea is expected to be the one an only "hill" of that time. I would like to visit that.

The African continent sits astride a geodetic high today, which some geophysicists visualize as the "hill" that the continents slid down.




As korjik said, they are there, the edges of the continental shelf.

Again, nothing against a "random crust break"

That was in response to your questioning why they weren't there. The answer was, they are there. You just weren't aware of them.


Ehm, continents re-colliding? Is this pro or against Pangaea or a random break?
You commented that Pangea dispersing should imply they converge--as if that were an argument against plate tectonics.

In fact, they do seem to have converged, dispersed, and re-converged on the far sides, again and again.

Relative
2014-Jan-18, 08:05 PM
In fact, they do seem to have converged, dispersed, and re-converged on the far sides, again and again.

Interesting, so kind of multiple Pangaeas? Where did you hear from this, I'd like to share the information.

novaderrik
2014-Jan-18, 11:45 PM
Interesting, so kind of multiple Pangaeas? Where did you hear from this, I'd like to share the information.

google it... i think it is thought that there were 2 or 3 single land masses before Pangaea- the Appalachian mountain chain of the eastern United States is a remnant of one these..

grapes
2014-Jan-19, 12:08 AM
Interesting, so kind of multiple Pangaeas? Where did you hear from this, I'd like to share the information.
I knew some of the original researchers.

As I said, look for "supercontinent supercycle"

Barabino
2014-Jan-19, 12:19 AM
Total mass of the continents is very small compared to the Earth, so the serious wobbling is still pretty minor.

yes, if you watch a globe with mountains in relief, be aware that their height is very exaggerated. Earth seen from space is much smoother than that!

19155

slang
2014-Jan-19, 12:20 AM
Afro-Eurasia-America, Gondwana, Laurasia, Pangaea, Pannotia, Rodinia, Columbia, Kenorland, Nena, Ur, Vaalbara.... home is where the heart is*.


*) On the bus!

Noclevername
2014-Jan-19, 12:22 AM
yes, if you watch a globe with mountains in relief, be aware that their height is very exaggerated. Earth seen from space is much smoother than that!

The way I learned it was "A billiard ball grown to Earth sized would have more surface relief than the Earth itself". I don't know it that's literally true but it sounds about right.

Delvo
2014-Jan-19, 05:24 AM
There's a reason why most people would only have heard of the most recent supercontinental arrangement. It's the only one that's been relevant during the parts of the evolution of life that are most talked about. Complex, macroscopic life barely goes back more than a half-billion years, but by then the planet had been here for around four billion, eight times as long.

grapes
2014-Jan-19, 05:46 AM
There's a reason why most people would only have heard of the most recent supercontinental arrangement.
The others were before their time? :)

Really, I think it's just because no one paid any attention to it. It was on the news...

WayneFrancis
2014-Jan-19, 03:08 PM
The Mid-Atlantic Ridge is another strong piece of evidence. We can see exactly where the plates separate and new crustal material is formed pushing the plates on either side in opposite directions. Run the clock back and, in simplistic terms, the coast lines would have been joined. Like korjik mentioned there is other data besides geological data to support Pangaea. Biology supplies many such pieces of evidence that are consistent with Pangaea especially when we look at not only the fossil record but things like genetic divergence between species within the same order but now separated by the Atlantic ocean.

Swift
2014-Jan-19, 06:00 PM
Interesting, so kind of multiple Pangaeas? Where did you hear from this, I'd like to share the information.
Nice website with maps (http://www.scotese.com/earth.htm) of the Earth's land masses going back about a billion years.

Look at Vaalbara (http://en.wikipedia.org/wiki/Vaalbara) and Kenorland (http://en.wikipedia.org/wiki/Kenorland) for the earliest supercontinents.

AGN Fuel
2014-Jan-19, 09:39 PM
The way I learned it was "A billiard ball grown to Earth sized would have more surface relief than the Earth itself". I don't know it that's literally true but it sounds about right.

Well, on some (rounded) numbers from Wiki, a British billiard ball is 56mm, the Earth has a diameter of 12,740 and Everest is 8.85km above sea level. Thus, the height of Everest above sea level represents 0.0007 the diameter of the Earth. That ratio for a billiard ball gives a "Billiard Ball Everest" height of 0.04mm - roughly the width of a human hair. i.e. the highest mountain chain (above sea level) on Earth is roughly equivalent to an eyelash on a billiard ball.

Strange
2014-Jan-19, 11:13 PM
Phil Plait, of Bad Astronomy, took a look at the claim that the Earth was smoother than a billiard ball. He concluded that the Earth was smoother but less round (http://blogs.discovermagazine.com/badastronomy/2008/09/08/ten-things-you-dont-know-about-the-earth/#.UZrBpmRAC9a), based on published billiard ball roundness tolerances. However, he couldn’t find any information on the size and shape of a billiard ball’s pits and bumps.

Fortunately for us, there are people who digitally scan bowling ball surfaces (http://www.youtube.com/watch?v=r5V3rFdAIMY).
http://what-if.xkcd.com/46/

filrabat
2014-Jan-20, 07:03 AM
Also, regarding the Mid-Atlantic Ridge, the closer you get to the ridge the younger the rock samples tend to be. Related to this, while rock is still in magma form, the molecules of the magma tend to align with the earth's magnetic field. The magnetic orientation of rocks on both sides of the ridge have the same magnetic pattern at a given distance from either side of the ridge (i.e. rocks at 100, 500, 1000, 2000, etc km from the ridge - on both sides of the ridge - have the same magnetic orientation). In fact, Iceland sits directly on top of the Mid-Atlantic Ridge, and in fact is the only part of the ridge that exists above sea level, and for 100s of km at that. As mentioned by grapes, Africa is another place where ridging is happening (more specifically, Ethiopia and the western border of Tanzania, plus Malawi, and maybe some parts of Kenya and Uganda.

Continental shelves- the continental shelves fit together even better than our present coastlines. In fact, the continental shelf is simply a part of the continent that is under the sea.

As for the biological and paleontological evidence, as mentioned earlier, perhaps the following illustration will help you out:

Imagine a giant baked chocolate chip cookie about 3 ft 3.37 inches (1 meter) wide, with ants and various other non-flying insect species across them (f.ex. ants and catepillars of moths). Further suppose that only one type of ant and caterpillar was found on only one section of this gigantic cookie. Then, suppose a giant tore the cookie in a dozen pieces, with some of those cookie tears going right through the area where that one type of insect crawled. if you saw widely separated cookie pieces inhabited by the same kind of ant and/or caterpillar AND you saw those two or more pieces seemed easy to fit like a jigsaw puzzle, then it's reasonable to conclude that those two now-separate pieces were formerly joined together; based on the 'neat fit' of the cookie parts and the fact that the same kinds of ants and catepillars exist on those two or more parts (the most striking real world geology version is South America and Africa).

So the Pangea theory is not just mere guesswork, it's an explanation of how a lot of data from many fields science not only fit together but reinforce other areas of earth and life science.

NEOWatcher
2014-Jan-20, 01:33 PM
Continents aren't "floating" on the planet's water
But they are "floating" on a sea of molten material.

novaderrik
2014-Jan-20, 03:17 PM
i remember when there was a major earthquake in Taiwan and had a coworker ask me how they could have an earthquake since they were surrounded by water.. i didn't even know where to begin...

grapes
2014-Jan-20, 03:18 PM
But they are "floating" on a sea of molten material.
No, it is not molten, it is not a liquid--not until the core-mantle boundary halfway to the center of the earth.

NEOWatcher
2014-Jan-20, 03:24 PM
No, it is not molten, it is not a liquid--not until the core-mantle boundary halfway to the center of the earth.
I stand corrected. Molten was the wrong word. It does flow, but the flow is ductile. Asthenosphere (http://en.wikipedia.org/wiki/Asthenosphere).

BigDon
2014-Jan-20, 05:02 PM
And to add to Filrabat's post.

This includes creatures that could not possibly survive a ocean rafting experience, like amphibians and land snails, who die in moments upon any contact with sea water. They leave fossils that predate human arrival so they weren't carried there by man.

Fresh water tetras exist in South America and African that have a common ancestor. (Though the African tetras aren't nearly as diverse.)

filrabat
2014-Jan-21, 09:45 AM
And to add to Filrabat's post.

This includes creatures that could not possibly survive a ocean rafting experience, like amphibians and land snails, who die in moments upon any contact with sea water. They leave fossils that predate human arrival so they weren't carried there by man.

Fresh water tetras exist in South America and African that have a common ancestor. (Though the African tetras aren't nearly as diverse.)

Don't forget primates in Latin America (monkeys specifically).