South America and Africa ‘fit together’ and were likely connected when they were part of Pangea.
How does this work, when there is a massive amount of ‘plate’ between them? South America is on the left of the South American Plate, and Africa is quite central on the African plate.
In: Planetary Science
This has already been answered fairly well on this thread years ago: [https://www.reddit.com/r/askscience/comments/b9bsc3/do_tectonic_plates_ever_change_in_size_and_or/](https://www.reddit.com/r/askscience/comments/b9bsc3/do_tectonic_plates_ever_change_in_size_and_or/)
The TLDR of it though is that the plates have cores that are quite stable, while the outer parts change a lot. So while the landmasses we’re used to are fairly stable, everything around them and between them is not. Which is why the central landmasses seem to fit together, despite having stuff in between them.
There are two kinds of plate: continental and oceanic. They’re made from two different kinds of rock. Continental plates are mostly made of granites while oceanic plates are mostly basalts. Granite is generally less dense than basalt so that, even though it’s cooler than the basalt mantle beneath it, it tends to float on it, the same way wood might float on water.
Within the semi-liquid mantle beneath the crust, convection currents can get established, causing hotter rock from the bottom to rise up, flow along the surface to cool, and then sink closer to the core again. If one of these upwellings happens to be below a continental plate, it will try to drag the rock along with it as it makes its way along part of its journey through the convection cycle.
That’s what’s believed to have happened to the continent that Africa and South America once were. An upwelling appeared in the middle of it, causing the two halves to get dragged in opposite directions until they were eventually split apart, with the gap much later becoming the southern Atlantic. If you look at relief maps of the crust below the Atlantic, you’ll see that there’s a ridge going along the middle of it. That’s where the upwelling is continuing to produce new rock from the mantle which is still pushing Europe and Africa further from the Americas at about a half-inch per year (plus or minus, depending on where you make your measurements).
Because all that plate didn’t use to exist. It emerged from the crust of the Earth, as molten material, as South America and Africa drifted apart, solidifying into new crust. The area where this happens is known as the Mid-Atlantic ridge and it is still spreading to this day at about 2.5 centimeters per year.
Latest Answers