Filed under: Uncategorized
I’d gotten away from posting on this, because I got heavily involved in local environmental politics. If you look up big developments and fire in San Diego for the last two years, I’ve been involved in that. Still am, really, which is why I can’t talk about it. Regardless, things are slowing down, and I’ve had a chance to read some interesting articles that might help with science fiction worldbuilding, so I’ll post them here.
And, of course, there’s US politics, which I’m not going to write about. I’m guessing that, if you’re reading this, you want a break from it? Regardless, it’s not clear whether we actually have any right to privacy at the moment, so I’m not going to post detailed diatribes over whether it would be reasonable to doxx certain high level judges in the US at the moment or not. I assume the answer is no, incidentally, but we’re not talking about that here.
Instead, this is about a new paper. There seems to be better evidence for what caused the PETM. The Paleocene-Eocene Thermal Maximum 56 mya is currently one of the better models for anthropogenic climate change. This article shows there’s some decent evidence that it was caused by volcanism, specifically, Iceland.
This didn’t surprise me. Iceland’s odd. Basically it’s a hotspot volcano like Yellowstone or Hawai’i, and during the Paleogene it was tracking across Greenland and into the widening north Atlantic. Now the hotspot is under the Mid-Atlantic Ridge, and I’m not sure if it will stay stuck there or keep moving. That hotspot X spreading center combination is unique in the world as far as I know. What’s a spreading rift, you ask? Well, in some models, it’s a row of hotspot volcanoes that…nevermind. I don’t know why some volcanism makes rifts (East Africa) and others make hotspots (the Pacific high islands).
It’s the details that matter, both for our current climate change nightmare and for worldbuilding on ancient SF planets.
–First off, the PETM carbon emissions were significantly higher than our fossil fuel supplies, so we could (if incredibly stupid) burn all our fuel and not get that hot. Since we’re burning fuel on the order of 300 years (most in the last 50 or so) and the PETM took 3,000-6,000 years, life WILL NOT adapt to our terafart as it did to the PETM. This is was incredibly stupid means. We’re not slowly boiling the climate frog, we’re microwaving it, and we need to control our emissions ASAP. Still, +8oC in the next 500 years seems to be off the table. Which is good, seeing how civilization’s rivets are starting to pop at a +1oC increase.
–Second, the clathrate gun hypothesis seems to be less supported. That’s the idea that methane released from the ocean floor can flood the atmosphere and rapidly raise temperatures. As the 2010 Deepwater Horizon blowout showed, when mass quantities of methane are released into the ocean, they get gobbled by methanotrophic archea and bacteria before they make it to the surface. So this isn’t (thank Gaia) as likely a doomsday scenario as it was 20 years ago.
And then we get to the proposed mechanism for how Iceland blew carbon, and it’s kind of cool. It’s also relevant for worldbuilding on a science fiction world.
The general problem with terrestrial worlds is that a biosphere that can support multicellular life has a limited lifespan. It requires oxygen (long story) and our planet, it took billions of years for that atmosphere to form (mostly because a huge amount of iron, sulfur, and other elements needed to be oxidized before surplus oxygen could flood the atmosphere). Another trap is that keeping carbon in the air requires active plate tectonics. Unfortunately, as planets age, absent some other source of energy, radioactive elements in the core decay, the core cools, the crust cools and thickens, and volcanoes and plate tectonics grind to a halt. This traps carbon underground, and multicellular life becomes impossible.
Thing is, our planet already has old rocks, and the PETM event shows an interesting way carbon can be blown back into the atmosphere.
From the article:
“CO2 and other gases can bubble out of tectonic plates as they dive into the mantle, percolating up into the underside of thick crusts like Greenland’s, and forming carbonate formations that can be stable for millions or even billions of years.
“If the crust is ever pulled apart by rifting, however, the trapped carbon can spill upward and erupt as rare carbonatite lava, which contains far more CO2 than standard lava. Indeed, such a process appears to be underway in East Africa right now, where a rift has begun to tear the horn of Africa away from the rest of the continent…”
“Similarly, the hot spot that burned through Greenland starting 60 million years ago could have mobilized any carbonate under its crust, Gernon says. When the rifting began to open up what today is the northeastern Atlantic Ocean, ‘you’ll have a huge amount of carbon venting.’
“Evidence of the carbon-rich melt is abundant on either side of the North Atlantic rift, the tectonic division that marks the old boundary between Greenland and Europe…”
The worldbuilding point of this is that, even on worlds with thick crust and little active rifting, carbon-rich lavas are possible (Ol Doinyo Lengai is the current example), and that’s how carbon will come back into the air.
If I had to guess, this will turn out to be the major mechanism for Earth’s mass extinctions: massive volcanoes hitting carbon-rich rocks. It’s almost certainly what caused the End Permian (the Siberian Traps burning through a huge, young coal field). The end-Triassic extinction is associated with the rifting open of the Atlantic (more thick, old rock getting cooked), and so on.
So, as long as flood volcanism and rifts can continue on a planet, both short term mass extinctions and long-term life may well continue. It will turn out to be both interesting and obnoxious if the long-term survival of life on Earth and Earth-like worlds is inseparable from the geology that also causes mass extinctions.
7 Comments so far
Leave a comment
Putting the life back in science fiction 
Good to have you back writing on these themes!
A question (because I didn’t read all the links): what’s the likelihood that a goodly portion of the carbon waiting to be expelled is in a form similar to natural gas, petroleum oil, etc? I’m just trying to sort out potential reactions.
Comment by SFReader June 27, 2022 @ 10:06 pmThanks!
My understanding is that oil, methane, etc. are uncommon. Most of what’s down there is kerogen (https://en.wikipedia.org/wiki/Kerogen) and material variations on the theme of limestone. While you can cook kerogen and release petroleum or natural gas, if there isn’t an impermeable layer (like a salt dome) above it, these just flow upwards until they bind with something else or ooze into the ocean and mostly get munched by microbes.
That said, you can go to deepcarbon.net and get sucked into how little we actually know about the carbon inside the Earth. For example, there’s some evidence that there’s more biomass in the deep crust (bacteria and similar) than there is on the surface, in the oceans, or in the atmosphere.
Comment by Heteromeles June 28, 2022 @ 12:17 am“ If I had to guess, this will turn out to be the major mechanism for Earth’s mass extinctions: massive volcanoes hitting carbon-rich rocks.”
Comment by Robert van der Heide July 1, 2022 @ 9:25 pmOr technology-using species burning fossil fuels. We assume we’re the first, but is that proven?
Pretty much. Coal started getting deposited in the Carboniferous (reason for the name), and not only did we have a lot of coal to mine, no one to my knowledge found paleosapient artifacts. I’m pointing to coal because coal seams preserve a lot of stuff (speaking from personal experience). We also had a lot of ancient petroleum to draw on, enough gold and diamonds that we could mine a kilometer or more below ground…This is stuff that wouldn’t easily be regenerated if it had been mined out. There’s also no plastic debris layer like we’re going to leave behind either.
Years ago I wrote a mediocre time travel novel called the Ghosts of Deep Time, about a time traveling metacivilization that left no trace of itself to avoid paradoxes. It’s kind of a fun idea, although I didn’t do it very well. But it got me thinking quite a lot about what kinds of evidence we leave behind and how to avoid it. So unless the ghosts of deep time are real, there weren’t paleosophonts on this planet prior to us.
Comment by Heteromeles July 1, 2022 @ 11:11 pmWhat fraction of the Carboniferous carbon have we burned? Run a few glaciers over South Africa and it’ll hard to find any traces of the gold and diamond mines.
The lack of microplastics is more telling.
Comment by Robert van der Heide July 7, 2022 @ 12:30 amThe amount of Carboniferous carbon we’ve burned is probably impossible to answer, because a lot of it burned at the end of the Permian in the Siberian Traps. The thing about fossil fuels is that if they get too deep, the material cooks and decomposes. Therefore, there’s not an infinite amount sitting underground. At some point, it’s all within mining range. My one datapoint for how fast erosion happens is from the Scottish Highlands, where 50 million years of various erosion took off about one kilometer of bedrock, IIRC. Given that the deepest goldmines are over a kilometer deep, I’d hazard a guess that grinding them away entirely would take 10s to 100s of millions of years, not just one ice age.
This gets to the question of traces. If aliens camped, grabbed some nuggets, and left, we’ll never see those traces. If paleosophonts had something on the scale of our global civilization…we’re leaving traces that will be detectable for hundreds of millions of years, including everything from microplastics, to bronze artifacts, to the “concrete galoshes” used by mobsters to bury send people to the ocean bottom (the concrete may remain after the feet rot) to depleted deep mineral beds. Things like that should be visible in the fossil record.
Comment by Heteromeles July 8, 2022 @ 4:57 amI was sorry to learn of your illness. My best wishes to you.
Comment by waldo August 12, 2022 @ 11:44 am