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Background Information:

252 million years ago, Siberia erupted, releasing enough lava to fill in a volume anywhere between one and four million cubic kilometers. Any time someone thinks "large igneous province", the Siberian Traps seem to be the first thing on his mind.

But the actual largest igneous province is the Ontong Java-Manihiki-Hikurangi Plateau in the depths of the Pacific Ocean. It erupted over 120 million years ago and released enough lava to fill in a volume anywhere between 59 and 77 million cubic kilometers.

Aim:

I am working on an earth-like planet with somewhat alternate history and I want to make a volcanic eruption on land (like the Siberian Traps) with a lava output equaling to that of Ontong-Java underwater eruption.

Question:

What necessary changes must I make in my world (with emphasis on geology and geography related changes) that would allow me to make a land-based volcanic action spew as much lava as the benthic eruption of Ontong-Java (59-77 million cubic km)?

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    $\begingroup$ @cobaltduck Just because a question might fit well in another exchange doesn't mean that it shouldn't be asked here. If OP didn't know about that exchange and wants to move it over there then fine, but if the question fits in worldbuilding then it belongs here too :) $\endgroup$
    – AndyD273
    Commented Mar 8, 2016 at 16:56
  • $\begingroup$ That being said, any question where the answer is "sure, if there is enough magma underground, why not?" probably doesn't have enough constraints to make it a good worldbuilding question. My only thought is that the one in the ocean has a lot of water pressing down, which may lead to more lava being forced out, while the one in Siberia doesn't have that. I don't know enough to say it really works that way though. $\endgroup$
    – AndyD273
    Commented Mar 8, 2016 at 17:03
  • $\begingroup$ There. Just reworded your question to make it precise and relevant to worldbuilding process :) Hope it helps. $\endgroup$ Commented Mar 8, 2016 at 17:27
  • $\begingroup$ That would confuse people into thinking that it's MY handwriting. $\endgroup$ Commented Mar 8, 2016 at 17:51
  • $\begingroup$ @cobaltduck Earth Science Stack Exchange is not interested in speculative scenarios. $\endgroup$ Commented Mar 8, 2016 at 17:51

2 Answers 2

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At first blush, an eruption in an ocean basin is a lot easier:

  • Thinner crust.
  • Lower lifting forces -- You don't have to push it up as far.
  • Buoyancy of water further decreases required force by about 40% (figgering basalt at s.g. 2.5

I grew up on the western edge of the central Washington flood basalts. And flood is the right descriptor. Very flat layers 10 to 80 feet thick.

I would expect some response similar to the way the crust rises and sinks at the end/beginning of an ice age. Since basalt and granite are similar in density, (basalt slightly heavier) you'd get something very similar to our existing igneous provinces except larger in scale. I don't think you could get an Olympus Mons here on Earth.

That said, consider the following scenario:

  • A large asteroid that has a relatively high content of radio isotopes hits the planet in an overtaking orbit, and does so at a relatively slow velocity. (Ok, this is improbable. Solar engineering gone wrong?)

  • The asteroid hits, and much of the matter sinks deep into the mantle, where it provides a continuous heat source creating a permanent plume.

  • The plume creates a chain of flood basalts as continental drift caries the tectonic plate over it.

This is pretty much the case of Yellowstone. I think the plume under Yellowstone at an earlier hotter stage was responsible for the flows that created the scablands of central Washington, as well as the Idaho batholith.

To get a larger province without global extinction, you need more time. You need to introduce CO2, SOx, and other aersols at a rate that is survivable.

In general it's not absolute values that concern you, but rate of change.

It's possible that you can create a world where the normal level of CO2 is several percent. People start having trouble at about 2% and serious difficulties starting at about 4%, but I expect solutions to this would evolve fairly quickly.

This introduces some notions for conflict: The heat balance is strongly driven by the amount of CO2 in the air, but also the particulates. Climate would fluctuate wildly, making for mass migrations both of animals and people. Evolving on such a planet the urge to seek greener pastures would be genetically encoded.

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  • $\begingroup$ So even if this eruption happened at a far younger date, it'd still be too thin to survive glacial advance? $\endgroup$ Commented Mar 8, 2016 at 22:15
  • $\begingroup$ I think it would be fine under glacial advance. Basalt is fairly hard. The weight of glaciers is signficant. Hudson Bay is rising in a rebound effect from going from having about 2 miles of ice on top of it. to having none. $\endgroup$ Commented Jun 3, 2021 at 13:47
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As the previous answer said, it would be much harder to get that amount of magma on a terrestrial surface.

But if it did, well...there's be very little left of life on Earth, if any. The Siberian traps devastated life and wasn't far from wiping out tetrapods. Something almost 20 times bigger is almost impossible to think about. I guess some animal could survive, but it would take likely till the present day, if not longer for biodiversity to recover (assuming it starts the same date as otl).

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  • $\begingroup$ Indeed. The biggest change is maybe large animals and plants have begun to re-evolve. Maybe. I wouldn't consider it unlikely life is still in the microbial stage. $\endgroup$ Commented Jun 3, 2021 at 15:46
  • $\begingroup$ "Devastated life" is to put it very lightly. It ended 83% of the entire Earth's biosphere. That period is also known as "the Great Dying". $\endgroup$ Commented Jun 4, 2021 at 12:05

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