I started thinking about tectonic plates, which, tyo say the leadt, is topical. Supposedly, at one time in history, all land was glued together in Pangea, or Gondwanaland or whatever name scientists want to apply.
That all nice and well. Loking at a map shows nthat iy’s not such abig stretch to see that S. America and Africa were once joined.
However.
There’s simething wacky, for me, in seeing all land lumped together in one big… lump. Since there wasn’t any intelligent design behind the creation of Earth, having all dry land lumped in one big continent, seems just too… convenient…
I’m not sure I’m making any sense here. Just saying.
Actually, not everything was joined together as Pangaea – I forget the details, but IIRC a couple of pieces of what is now China were “out there” as microcontinents (Greenland/Australia-size mega-islands).
Read it as coincidental – when you have a dozen or so pieces floating around, and subject to particular motive forces that tend to push them in a given direction, sooner or later they will conjoin. It appears to happen approximately once every 300 million years – what was Pangaea came together in the Carboniferous and Permian from previous pieces, most of which were the results of the breakup of a previous megacontinent labelled “Rodinia” which was around in the latest Precambrian.
For those who might care, when Pangaea split in two, the half that wasn’t Gondwanaland is referred to as Laurasia (as opposed to Laurange, the Doper from Montreal who lives on a remnant of Laurasia ;)).
Well, given that the ancestors of the platypus date from the Jurassic, next period after Gondwanaland broke up, and it’s always considered to be the definitive proof of use of reality-warping substances by a creator, you might have a point.
hmm, all very interesting- but since I’m learning here-which was which and in what order… let me help “once upon a time…” (good start eh? :P) the Earth was land massed in only one region called_____ -(which brings up th-at question, approxiatemately wh-at region?; like around Europe and the rest or was all this on top of America’s GP coordinates?) Too many people that know of such a period don’t know the specifics and since you brought it up, go ahead and educate your at least 1 pupil lol so I don’t have to suffer know only so-me of the details Ah yeah, a shout out to to Julie! lol later
Gondwanaland sprawled across the Southern Hemisphere, with southern Africa located over the South Pole and the greater part of the land mass easterly of it, IIRC. As for Pangaea, it was in a similar layout; I recall seeing a map of paleo-North America at approximately the right time period in which the Equator ran diagonally across the U.S., approximately from Jacksonville FL to Vancouver BC, the areas that would now be south and west of that line being in the Southern Hemisphere tropics and the rest in the Northern tropics.
I have to admit, Laurasia and Gondwanaland hold places in my heart as some of my favourite words.
The real issue here is why Pangaea was the only land above sea level. That I don’t know, but I’m certain there’s some geological explanation which doesn’t require any sort of deviation from science. There is ‘land’ all over the earth, we just only consider land not covered by water as real land.
Funny how a bunch of folks have suddenly taken an interest in plate tectonics. I was wondering the same thing.
It appears that it wasn’t really much of a coincidence. Tectonic plates have been swinging back and forth since much earlier in the Earth’s existence. Before there was Pangaea there was superconinent called Rodinia. The plates in it swung out and traveled around the globe before (mostly) smashing back into each other, forming Pangaea. I’m guessing that there were even more supercontinents before Rodinia.
Now as to why these plates keep oscillating between different supercontinents, I have no idea.
After reviewing Tom’s USGS link and my reference book, which I should have gone to in the first place, what I describe above is from the Silurian – i.e., about as far before the Permian as the Cretaceous was after. :o
Continental rock is less dense than seafloor rock – plate techtonics occurs in the deep stuff, and the continents just sort of float on top and go along for the ride. And occasionally get rammed together, or straddle a spreading center and get torn apart, or sucked down into a trench then spat up again as a volcano…
As I understand it, it took a while during the early part of earth’s history for the various peices of “continental” crust to crash into each other & congeal into continents.
My all time favorite pseudo-political bumper sticker: “Reunite Gondwanaland!”
(And Hi everybody … a newbie here; this seemed like a good thread to jump into & get my feet wet, so to speak … )
Wow! That is the coolest website I have ever visited. Thank you.
In response to the OP, IANA geologist, but it appears from the animation provided above that the continents are pushed apart by a jealous mantle all the way around the globe until they meet again on or near the other side. Of course on a sphere, sides exist only to the POV of an observer.
IAMAGeologist either (though I hope to be someday), however it is my understanding that What is now South America and Africa were broken up by a divergent boundary (with magma oozing and cooling around it) that kept bringing up new rock material that pushed them away from each other.
Evidence of this is shown by newer material being closer to the rift and older material being farther from either side of the boundary.
We do know this happened because fossils and rock types found in Western Africa and Eastern South America (right where they look like they would fit) match.
To add:
The reason some plates are forced towards each other is because of convection that occurs in the Earth’s plastic mantle.
If you’ve seen a beaker of boiling water, the hotter water moves upward and father from the source of heat, cools, and comes back down. This process occurs throughout the plastic mantle.
Now, as some of the plastic mantle moves, it drags some of the crust with it, forcing some parts together and creating convergent boundaries.
I expect somebody with more experience and knowledge will be along shortly to correct me if I am wrong.
Ah yeah, a shout out to to Julie! lol later