Cosmology and astronomy
- Plate tectonics: Difference between crust and lithosphere
- Structure of the earth
- Plate tectonics: Evidence of plate movement
- Plate tectonics: Geological features of divergent plate boundaries
- Plate tectonics: Geological features of convergent plate boundaries
- Plates moving due to convection in mantle
- Hawaiian islands formation
- Compositional and mechanical layers of the earth
- How we know about the earth's core
Pangaea - the idea of Pangaea and some of the evidence behind it. Created by Sal Khan.
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- so when the continents were moving away from each other, were they kinda floating like an ice berg? A super slow iceberg of course. But since the plates are under water, did the ocean move with us?(19 votes)
- The oceans are the large bodies of water between continents. Land masses and water ways change together. Most people find it easier to talk about the movement of land rather than a movement of oceans.
If the movement of plates is bringing two land masses toward each other raising the relative elevation of that region the water will narrow and eventually go away. When land masses split apart and reposition themselves new waterways form.
In the time of Pangaea Antarctica was landlocked so there was no Arctic Ocean. If we follow the movement one can see that Mediterranean Sea used to be an ocean and that the Indian Ocean is also relatively new.
- where is North America during Pangea?(13 votes)
- According to popular models North America was oriented with about a 90 degree tilt from how it currently is. Mexico would have been to the West, Canada to the East, the Gulf of Mexico to the South and the Rockies to the North. The Florida Peninsula sat at the border between the continents of South America and Africa. The Gulf of Mexico would have bordered the northern tip of South America where Columbia and Venezuela are. The Appalachian Mountains and eastern coast of the United States would have hugged the Northwest corner of Africa and Scandinavia would have been nest to the northern trunk of Canada.
See link below for a map to help visualize.
- Where does Hawaii fit into Pangaea?(17 votes)
- It Doesn't. Hawaii formed kind of independently through volcanic activity. It didn't even exist at the time Pangaea was dominant. Older Hawaiian islands were already formed, but definitely not Hawaii.
PS: I know this is a late reply. By like, 6 years.(3 votes)
- Is there a species that is alive today that was alive in the time of Pangaea?(8 votes)
- Crocodiles have changed very little since the time of Pangaea. Sharks too are an even older species.(5 votes)
- Through the formation and breakup of Pangaea we see the that every continent has been slowly moving and changing position. Except Antarctica, which has stayed at the South Pole.
Why has Antarctica stayed so stable in comparison to the rest of the planet?(6 votes)
- I do not know if this is correct, but I will offer this hypothesis:
The earth is spinning, and the spin is partially responsible for the direction of the "currents" in the mantle that cause the continents. Antarctica is located right at the end of the axis of rotation. It is easy to imagine that that's a sort of stable spot, since there won't be a lot of tangential force there from the earth's spin. So once a plate lands at the end of an axis, it might tend to stay there.(7 votes)
- Could the continents move back together again.(4 votes)
- Yes, in fact they likely will. For example, the Pacific Ocean is slowly shrinking, while the Atlantic is growing. You can also look up something like “future continental drift” if you want to see predictions of what future supercontinents might look like.(7 votes)
- is it possible that pangea will reform again in time(3 votes)
- Probably not the way it was. The plates may fit together another way. However, another supercontinent will form some way.(6 votes)
- When Pangea moved apart, what happened? Like, did the ocean flood in the cracks or stay dry for a while? If not, what was there(magma or rock)?(4 votes)
- When pieces of Pangea started moving apart, there would have been a rift valley in the continent (a modern example would be the great rift valley in Africa where two subplates are currently diverging). Once Pangea's plates got further apart, the space in between would have filled up with oceanic crust (lava at first, then cooling to rock). The ocean would fill in as soon as the elevation went below sea level.(4 votes)
- Based on the maps of different stages' of plates movement since Pangaea in this video, the Eurasian plate seems staying at it's location(relatively speaking) while all other plates have been moving around a lot. I am wondering why?(4 votes)
- Good question! Well, (this is just a thought) maybe ocean currents might be pushing other plates more than other plates. I don't know, maybe there is another more scientific answer!(2 votes)
- How do we know the continents are moving in the same direction as 200 million years ago¿(4 votes)
- The problem with that is we don't. We can only guess, because the continents are moving, but at such a miniscule rate it isn't funny.(2 votes)
We know that new plate material is being formed, and these lithosphere plates on the surface of the Earth are moving around. And that might raise the question in your brain-- what happens if we kind of reverse things? We know the direction they're moving in. What does that tell us about where they came from? So let's just do the thought experiment. Right now, South America and Africa are moving away from each other, because of new plate material being created at the mid-Atlantic rift. Let's rewind it. Let's bring them back together. We know that India is jamming into the Eurasian Plate right now, causing the Himalayas to get higher and higher. What if we rewind that? Let's bring India back down towards Antarctica. Same thing with Australia. We have new plate material being formed between Australia and Antarctica that's making the continents move apart. Let's bring them back together. Let's rewind the clock. Even North America-- it's not as obvious from this diagram, but if you actually look at the GPS data, it becomes pretty obvious that North America, right now is moving in a counterclockwise rotation. So let's rewind it into a-- let's go back, moving it in a clockwise direction. Let's, instead of Eurasia going further away from North America, let's bring it back together. And so what you could imagine is a reality where India, Australia are jammed down into South America-- sorry, into Antarctica. South America and Africa are jammed together. North America is jammed in there. And essentially, Eurasia is also jammed in there. So it looks like they all would clump together if you go back a few hundred million years. And based on, literally-- based on just that thought experiment, you could imagine at one point, all of the continents on the world were merged into one supercontinent. And that supercontinent is called Pangaea-- pan for entire, or whole, and gaea, coming from Gaia, for the world. And it turns out that all of the evidence we've seen actually does make us believe that there was a supercontinent called-- well, we call it Pangaea, now. Obviously, there probably weren't things on the planet calling it anything back then. Or, there were things back then, but not things that would actually go and try to label continents that we know of. But all of the evidence tells us that Pangaea existed about 200 to 300 million years ago, roughly maybe 250 million, give or take, years ago. And I want to be clear. This was not the first supercontinent. To a large degree, it's kind of the most recent supercontinent. And it's easiest for us to construct because it was the most recent one. But we believe that there were other supercontinents before this. That if you rewind even more that you would have to break up Pangaea and it would reform. But we're now going back in time. Or that there were several supercontinents in the past that broke up, reformed, broke up, reformed. And the last time we had a supercontinent was Pangaea, about 250 million years ago. And now it's broken up into our current day geography. Now, I won't go into all of the detail why we believe that there was a Pangaea about 250 million years ago-- or, this diagram tells us, about 225 million years ago, give or take. But I'll go into some of the interesting evidence. On a very high level, you have a lot of rock commonalities between things that would have had to combine during Pangaea. And probably the most interesting thing is the fossil evidence. There are a whole bunch of fossils. And here are examples of it, from species that were around between 200 and 300 million years ago. And their fossils are found in a very specific place. This animal right here, cynognathus-- I hope I'm pronouncing that right-- cynognathus. This animal's fossils are only found in this area of South America on a nice clean band here, and in this part of Africa. So not only does South America look like it fits very nicely into Africa. But the fossil evidence also makes it look like there was a nice clean band where this animal lived and where we find the fossils. So it really makes it seem like these were connected, at least when this animal lived, maybe on the order of 250 million years ago. This species right over here, its fossils are found in this area-- let me do it in a color that has more contrast-- in this area right over here. This plant, its fossils-- now, this starts to connect to a lot of dots between a lot of cont-- its fossils are found in this entire area, across South America, Africa, Antarctica, India, and Australia. And so not only does it look like the continents fit together in a puzzle piece, not only do we get it to a configuration like this if we essentially just rewind to the movement that we're seeing now-- but the fossil evidence also kind of confirms that they fit together in this way, This animal right here, we find fossils on this nice stripe that goes from Africa through India, all the way to Antarctica. Now, this only gives us evidence of the Southern Hemisphere of Pangaea. But there is other evidence. We find kind of continuing mountain chains between North America and Europe. We find rock evidence, where just the way we see the fossils line up nicely. We see common rock that lines up nicely between South America and Africa and other continents that were at once connected. So all the evidence, as far as we can tell now, does make us think that there at one time was a Pangaea. And, for all we know, all the continents are going to keep moving. And maybe in a few hundred million years, we'll have another supercontinent. Who knows?