How to make Zealandia a thing IRL

[fredinno]

Well, after watching this video

 

it got me wondering if such a thing could exist geologically IRL so that it is still above water

(aka- what uplift processes would be required to push it to the surface?)

 

The issue is that

Zealandia (and its sister, West Antarctica) are stretched continental shelf built from the remains of the coastal continental shelves of Gonwanda.

 

That is a major problem.

And I can't get answers anywhere else. I need help. It's for alternate history.

[UnusualAttitude]

18 hours ago, fredinno said:

That is a major problem.

Indeed it is, but the forces at work here are relatively simple: it's all about isostasy, or Archimedes' principle applied to the Earth's crust and mantle (or, more precisely, the lithosphere and the asthenosphere). 

Lighter continental crust "floats" on the Earth's more dense mantle, which over geological timescales acts as a viscous fluid. The problem is that when Zealandia broke away from Gonwanda 100 million years ago, the continental crust was stretched out, became thinner, and therefore the continental surface "sank" in relation to sea level. 

In your alternative history, (and if all other things are equal), I can't see any way of keeping Zealandia afloat, unless plate tectonics didn't actually stretch the continent as much. But this would mean that Zealandia would have a very different size and shape compared to her present (submerged) form. Would this be a problem for your alternative history?

Actually, I do have a couple of ideas (and you'd have to get the opinion of a much more up-to-date geologist than myself, both of them may be silly, but since no-one else answered ):

- Zealandia's break away from Australia happened much more recently in geological history, and the continent has not yet reached isostatic equilibrium, so more of the continent is still above sea level, albeit slowly sinking. Not sure this works out over millions of years, though. More like tens or hundreds of thousands.

- There is a mantle superplume beneath Zealandia that is causing crustal uplifting. A bit like in the Pacific or Eastern Africa.

Geology is such an awfully complex science, and an astoundingly young one, too. We got to the Moon by the time we figured out plate tectonics. That's why I gave it up for much simpler rocket science....

[fredinno]

Thanks!