Hello, everybody! Today I've decided to try out a new kind of post - one where we look at the history of Earth, one where we look at a different part of Earth's history at a time! Let's get started!
Precambrian Supereon (4,600 to 541 million years ago)
Hadean Eon (4,600 to 4,000 million years ago)
The Hadean started with the formation of Earth. A good way to describe Earth at the time would be 'quite like Hell'. A fair amount of the surface was molten, volcanoes were everywhere and a leading theory states that Earth was hit by an object the size of Mars. After that, amounts of both planets were thrust out and became the Moon. Ouch. We've actually found a crystal dating from this time. It's zircon, or zirconium silicate (ZrSiO4). How it survived is anyone's guess... It's quite clear why this eon was named after Hades.
Archaean Eon (4,000 to 2,500 million years ago)
And now we say hello to life! That's right, life on Earth started only 600 million years after the formation of the planet. First, we had simple self-replicating molecules of RNA. Then we eventually got DNA after that. This is when bacteria first appeared as well! But we still couldn't survive then - Earth's atmosphere still had no oxygen in it. It was full of things like hydrogen sulphide and ammonia... nasty stuff! Plus, the Sun made even more UV rays then than it does now... and there wasn't any ozone layer! Any and all life on the surface would've been fried.
Proterozoic Eon (2,500 to 541 million years ago)
Now we get oxygen! A while before this eon started, photosynthesis was already in full swing. Oxygen was released, but then it was immediately removed from the atmosphere. But over millions of years, photosynthesis filled up all of the oxygen 'sinks'. And then it happened. Oxygen was let loose into the atmosphere. Wherever it reached, oxygen killed most life. Sure, saying that now seems... weird. But most organisms then couldn't deal with the toxic byproducts of oxygen (we can.) And then Hell froze over... if you consider Earth then to have been Hell - another theory states that the Earth was covered in a blanket of ice. Chilly! And this is also when the Earth's supercontinent cycle began, with the formation of the supercontinent Rodinia.
And then diversity exploded...
But that's a topic for another week. I'll be seeing you next week!
-A personal update-
I just wanted to mention two things. First, last week, I got something wrong. The link to my Instagram profile is on the left of the page, not the right. And secondly, I want to stress it's only a blog account. I used to post any pictures in the Week Overview posts, but now they're gone (well, maybe, but if I do bring them back, they won't be every week.) So I decided to make an Instagram account to share the pictures - even if I couldn't on the blog itself. (Our cat Hebe is about as personal as I'm going to get. - here's an example.)
After all, if I didn't want my posts to be public, I'd make my account private!
Anyway, I'll see everyone next week, so take care for now!