Wednesday, March 24, 2010

Dinosaurs, Runaway Volcanism, Change, and Evolution

"Dinosaurs Rode Volcanic Armageddon to Victory"
Wired Science (March 22, 2010)

"Geologists have turned a series of 200 million-year-old lake-bed sediments into an epic narrative of the dinosaurs' journey from ecological obscurity to Earthly supremacy, a mystery that has lingered even as their disappearance is explained.

"The dino path to dominance appears to have been cleared when the supercontinent Pangea cracked, setting off 600,000 years of volcanic activity that wiped out the dinosaurs' crocodilian competitors.

" 'This is the strongest case for a volcanic cause of a mass extinction event to date,' wrote geoscientists in a paper published March 22 in the Proceedings of the National Academy of Sciences.

"From 250 million to 200 million years ago, dinosaurs were just upstart lizards. The planet was dominated by a family of vaguely crocodile-like animals called crurotarsans that filled every major ecological niche, from slow-munching herbivores to fleet predators...."

"...From 250 million to 200 million years ago, dinosaurs were just upstart lizards. The planet was dominated by a family of vaguely crocodile-like animals called crurotarsans that filled every major ecological niche, from slow-munching herbivores to fleet predators.

"About halfway through that period, known as the Triassic, an asteroid struck Earth. Many of the planet's species went extinct, but the crurotarsans weathered the storm. Then, 25 million years after that, in what's known as the Triassic-Jurassic extinction event, the crurotarsans and at least half of all other animal species vanished. Exactly why isn't known, but scientists now have a pretty good idea...."

Like I've said before, change happens.


(from Wired Science, used w/o permission)

Those aren't dinosaurs: they were crurotarsans, those "crocodilian competitors" critters that got wiped out about 200,000,000 years ago (closer to 199,600,000 - maybe - but who's counting?) Crocodile-like they are, but the first thing I thought, seeing the one on the left, was 'what's a picture of a pike doing in this article?'

You Thought You Had a Bad Day?


(from Wired Science, used w/o permission)
"CAMP" stands for Central Atlantic magmatic province, by the way. It's "a 3.5 million-square-mile lake of lava" that formed during the 600,000 or so years when the Atlantic was born.

That's a map of Earth, about 210,000,000 years ago, before about 600,000 years of volcanism in what's now the Atlantic Ocean apparently killed off a whole lot of creatures: including the crurotarsans. Bad news for them, good news for the dinosaurs. And, eventually, us.

Let's go over some of the (approximate) times mentioned in the article
  • 225,000,000 years BP (before present)
    • Asteroid hits Earth
  • 200,000,000 years BP
    • Heavy volcanic activity starts
    • Pangea breaks in two
      • We call that break "The Atlantic"
  • 199,400,000 years BP
    • Heavy volcanic activity ends
      • Elapsed time: 600,000 years
      • Crurotarsans are extinct
        • Leaving room for dinosaurs
  • 65,000,000 years BP
    • Asteroid hits Earth
      • Dinosaurs are extinct
      • Leaving room for mammals
        • And, eventually, humans
For the last dozen millennia or so, humanity's been living in a relatively tranquil warm spell during one of this planet's glacial periods. Or maybe at the end of the more recent period of continental glaciation. Last I heard, the jury's still out on that one.

Sometimes it's hard to remember that 15,000 or so years is a fairly short time on Earth's history. It isn't even close to being on the same order of magnitude as, say, 65,000,000, 200,000,000, or 225,000,000.

And, that life on Earth has been through asteroid hits, massive volcanic events, and a glacial epoch where continental glaciers reached all the way to the equator. (" 'Snowball Earth,' Evolution, and Really Old Rocks" (March 16, 2010)) The lava flow mentioned in this article covered around 3,500,000 square miles. That's very roughly 1.8% of Earth's surface. By comparison, the United States of America is a little bigger than that, but not by much.

Today's emphasis on how endangered the koala, panda, and Bee Creek Cave Harvestman spider is, I think, laudable in some ways. At least it's a change of pace from the 19th century silliness that apparently assumed that every natural resource was effectively infinite.

But although I think that Harvestman spiders in the Bee Creek Cave may be in danger of dying out, I'm not particularly worried about life on Earth as a whole. Mother nature is a tough old mother. More like Queen Boudicca than Clara Bow ("Frail, Delicate Little Mother Nature?!" (December 20, 2009))

I'm not very worried about humanity, either. We've only been around for maybe 1,600,000 years - maybe longer - but that period included one of Earth's seven major glacial periods. We made it through that - quite possibly developing much of our early technology while dealing with the changing conditions. We're opportunistic omnivores, there are well upwards of 6,000,000,000 of us, and we have a history of bouncing back from catastrophes. Remember the Black Death?

I think we'll prove as hard to kill as rats - maybe even cockroaches. I'll grant that's not a flattering comparison: but I think the reputation those critters have is due in part to their being, as a group, nearly indestructible.

More:

2 comments:

Brigid said...

I can't believe I'm saying this, but I think pike are a bit prettier than that... thing.

Brian, aka Aluwir, aka Norski said...

Brigid,

I see your point. And yes: that's definitely a - - - thing.

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