Imagine that some kind of catastrophic event takes place on Earth, like a gigantic eruption, and half the planet ends up transformed into a hell-like hemisphere, with volcanoes and seas of lava (like Mustafar from Star Wars).

Something like this: Earth divided in two halves, one good, the other is hell

At some point, the lava would solidify forming an enormous range of volcanic rock mountains surrounding the equator, dividing the world in two defined halves. I guess that this ring would be impassable due to the high temperatures (and maybe poisonous air?) and people wouldn't even dare to get close to it.

How would this affect to climate? I've been thinking about oceanic currents, global winds, atmosphere composition, tectonic plates movement... And of course, what would be the ecosystems be like? Would we still have the same biomes with the same vegetation and fauna?

I've been chewing on this for a while and I would like what you guys think about this. Thank you very much!


OK, my bad. I've asked something too broad and big. I appreciate the feedback though. Let me fix this up a bit.

I know for sure there would be a massive extinction and the Earth would be an uninhabitable planet for eons. Please, don't focus so much on what would happen immediately but on a very, very long term (once the planet had been recovered). I think of this catastrophe as an event which has taken place in an very remote past, which no one is really aware of (since, as I posted before, people wouldn't dare to get close to the Equator), and which has reshaped the world completely.

But my major concern is the climate. I'd like to build a world with a consistent science-based explanation for its climate. I don't buy that "North is cold, South is hot" trope (I know I'm talking about southern hemisphere but please remind that cardinal direction is arbitrary). As far as I know, winds are just air currents moving between areas of different pressures, which are caused precisely by heat. One example of this is the monsoon, which I think is a really cool phenomenon.

Summing up: what would be like the climate of a planet whose southern hemisphere is a giant crater of lava. Would a single hemisphere climate system be viable? Would it be something similar to our current climate?

Thank you very much and, once again, excuse me for my broad question. My fault completely. Or maybe my question is just plain dumb. Sorry in any case.

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    $\begingroup$ Welcome to WorldBuilding! Interesting first question, but a bit broad (the character limit for an answer is 30,000 ;) ). We are not a general discussion forum, but a "Question and Answer"-site. Please try to narrow down your question. For example by focussing on winds or oceanic currents at first. You can use the answers you get and incorporate them into follow-up questions later. If you have a moment please take the tour and visit the help center to learn more about the site (and earn a badge). Have fun! $\endgroup$
    – Secespitus
    Apr 22, 2017 at 23:07
  • $\begingroup$ I'm voting to close this question because it is purely what-if question $\endgroup$
    – MolbOrg
    Apr 23, 2017 at 0:45
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    $\begingroup$ @astroman this comment is plain wrong! Nobody is going to delete a question just because it has too little details. What will happen though (or already happened) is that it is put on hold. This allows the OP to refine their question while stopping people from answering something that isn't yet clear, thus the answers they spend time and energy building are mostly prevented from being invalidated. Please read up on how this site works instead of spreading half-truths! $\endgroup$
    – dot_Sp0T
    Apr 23, 2017 at 9:00
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    $\begingroup$ @astroman closed is not deleted $\endgroup$
    – dot_Sp0T
    Apr 23, 2017 at 16:29
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    $\begingroup$ @astroman Placing a question on hold is intended to give the OP the opportunity to edit their question and make it acceptable and fit for answering. RE your closure cycle, too often not enough effort is made to improve questions instead of simply putting them on hold. It's a Catch 22. $\endgroup$
    – a4android
    Apr 24, 2017 at 2:21

1 Answer 1


Well, the initial event would probably kill all complex life on Earth, maybe all life depending on how neatly contained it is at the hemisphere-boundary.

Most of the Southern Hemisphere is currently covered by ocean, so to turn it into a lava world you'd have to boil that away. But the ocean is connected all around the world, so to remove the ocean from the Southern Hemisphere you'd have to remove all the ocean - which would make the earth uninhabitable (both from lack of water and from the boiling oceans steaming everything on land to death).

So you wouldn't get much of an ecosystem, or even an 'Earthlike' hemisphere. At most, some endolithic microbes would survive, too deep in the rock to be steam-boiled and using underground water supplies unconnected to the ocean.


However, you could probably get a situation like this if the Earth was re-terraformed after the event (say, by people in colonies on the other planets/asteroids with samples of Earthly life - maybe they knew the disaster was coming in time) but that re-terraforming is so far limited to the Northern Hemisphere.

If the equatorial ring of volcanic mountains was high enough, it would shift the global wind patterns dramatically - the Himalayas do. probably winds in the northern hemisphere would be mostly contained to it (even now, the 'equatorial doldrums' somewhat separate the wind patterns of the two hemispheres).

Ocean currents will be limited to the Northern Hemisphere too; either the Southern Hemisphere has no ocean, or (if the lava has cooled to volcanic rock by this point and enough water survived as steam to re-condense into oceans) the two hemispheres' oceans would be totally separated by the equatorial mountain-ring.

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    $\begingroup$ ...and if the initial event somehow didn't kill all complex life, an entire hemisphere filling the atmosphere with unbreathable, corrosive gas certainly would. $\endgroup$
    – user535733
    Apr 23, 2017 at 2:05
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    $\begingroup$ The Permian-Triassic extinction involved much smaller lava flows, yet killed off about 97% of all species. Though if you want to be technical, rather more than 50% of Earth - the ocean floors - is covered by lava. It's just that it was errupted slowly, over 100 million years or more. See e.g. plate tectonics and seafloor spreading. $\endgroup$
    – jamesqf
    Apr 23, 2017 at 4:20
  • $\begingroup$ @user535733: well, depends on what you mean by complex life - there are little animals (loriciferans -- actual animals, not single-celled prokaryotes) on the bottom of the Mediterranean that live without oxygen. I said 'probably' because biologists are discovering more bizarre exceptions that survive in weird conditions like that all the time... $\endgroup$ Apr 24, 2017 at 10:30

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