Hello, everybody - and welcome to this week's blog post! (Sometimes, I wonder if this is actually a blog...) Regardless, let's get going!
The Ordovician Period - 485.4 to 443.8 million years ago
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| This is how the continents looked 470 million years ago, near the beginning of the Ordovician. Source: Wikipedia |
485.4 million years ago, the Cambrian transitioned into the Ordovician. This was marked by a fairly big extinction event that crippled the trilobites (but they still hung on until just before the Triassic.)
However, unlike the Cambrian, which overall saw oxygen levels so high that lightning could set the air on fire, the Ordovician's levels were lower than today's, at around 13.5% O2 (68% of today's levels, which are 20.9% O2.) And for anybody who's panicking about the levels of carbon dioxide in the atmosphere being 400 parts per million, the Ordovician's levels were around 4,200 ppm. (Which then doesn't make sense considering the ice at the South Pole...)
The Ordovician had a life explosion of its own - the amount of genera living in water increased by four times! It's also when coral reefs started to first appear - some of the few things that have remained relatively unchanged since then.
At the end of the Ordovician, there was an ice age. Because of this, much of the life that was firmly adapted to the warm, tropical seas died. Then there was another ice age. But after the second one ended, sea levels stabilised and the life that survived filled the niches left by those that died.
Next up will be the Silurian, with increasing oxygen, sporadic seas - and sharks! Definitely sharks.
Anyway, I'll see you all next week, so goodbye for now!
The Ordovician had a life explosion of its own - the amount of genera living in water increased by four times! It's also when coral reefs started to first appear - some of the few things that have remained relatively unchanged since then.
At the end of the Ordovician, there was an ice age. Because of this, much of the life that was firmly adapted to the warm, tropical seas died. Then there was another ice age. But after the second one ended, sea levels stabilised and the life that survived filled the niches left by those that died.
Next up will be the Silurian, with increasing oxygen, sporadic seas - and sharks! Definitely sharks.
Anyway, I'll see you all next week, so goodbye for now!