How to Build the Fictional Continents Using Our Real Continents

Question

Presented here is a map of Earth with the fictional continents resurfaced, by the Redditor "Stagman1111":

Source

From left to right, the presented additional continents are Mu, Atlantis and Lemuria. It's a popular alternate history trope to imagine them being separate continents made independently of each other.

But I'd like to do it differently. In a point of departure anywhere between 157 and 145 million years ago, some of our continents (for clarity, continents like North America and Europe, etc.) had split themselves apart to create Mu, Atlantis and Lemuria. But which pieces from which continents would make the best candidates to create those three continents?

Answer 1

Atlantis is hard, the others are...less hard.

Mu, which I presume is to the left of North America, would come from the San Andreas fault zone, which is already basically not attached anyway and moving with respect to the continent, just in the wrong direction to produce that specific continent you want.

Lemuria would be the Indian subcontinent, which in the real world is actually moving the other way to push up the Himalayas.

Atlantis is harder because as far as I know there is no fault zone anywhere near where it should be except on the ocean floor. There is a fault at the southern tip of Africa called the Cape Fold Belt, but that would put Atlantis in the southern, rather than Northern, hemisphere and probably somewhere between the Atlantic and the Indian oceans.

Now...please note a couple of things:

1. 180 million years ago the continents were all locked together in Pangea, which was just starting to break apart. They wouldn't have been in the same places as now, so neither would your three lost continents

2. If these plates actually did break apart in the "wrong" direction as I described, then I can't predict what that would mean for the evolution of the earth. For instance, if India moved the other way, then you don't get the Himalays. Without the Himalayas you don't get the Gobi Desert or the dry steppes of Asia. Without those...

Answer 2

Atlantis is easy: just Iceland further south. The obvious solution is have the Azores Plateau be larger and higher so it breaks the surface.

Lemuria could be a chunk of Gondwanaland that gets pulled from Africa when India separated and started barrelling north to ram into Asia. Note that this is pretty much the origin of Madagascar, so what you can have is that the chunk that becomes Lemuria is a larger piece of Gondwanaland. Madagascar wouldn't exist, and the shape of southern Africa would be different as the large fragment was pulled out further into the ocean by the movement of the Indian Plate.

Mu, so long as you show some flexibility regarding size, also not that hard. The western bit of North America largely consists of fragments of continental crust and oceanic crust that were welded onto the North American craton as oceanic plates subducted and carried them along. What you'd want in this case is that the subduction zone occurs further away from the craton, initially creating an island arc chain that grows larger and larger through it's own volcanism and these bits of continental crust that start collecting. Then the subduction dies out leaving a welded-together terrane of the west coast. Of course, this also means that North America isn't as wide as some of the fragments that formed it ended up as part of Mu.