Knjigice
Learn-about book · Dinosaurs & space
Earth, 4.54 Billion Years
Earth and it's 5 greatest extinction events
Also in: Zemlja, 4,54 milijarde let (Slovenian) · Zem, 4,54 miliardy rokov (Slovak)
Earth Is Very Old
Earth is 4.54 billion years old.
If that whole story were squeezed into one single day, people would appear in the last six seconds.
Five times, life here almost ended. Five times, it came back.
1
For Ages, Life Was Too Small to See
The first living things appeared more than 3.5 billion years ago: single cells in warm shallow water.
For almost three billion years, that was all life was.
No trees. No animals. Just green slime, quietly making the oxygen we breathe.
2
Extinction Nb 1: Ice at the Bottom of the World
444 million years ago the world froze. Ice locked up the water and the warm shallow seas drained away.
About 85 of every 100 kinds of animal vanished.
Nothing lived on land yet. On land, there was nothing to lose.
3
Extinction Nb. 2: The Reefs Went Quiet
372 million years ago the great reefs died.
Dunkleosteus hunted in that green water: a fish as long as a car, with no teeth at all. Its jaws were blades of sharpened bone.
Reefs would not grow back for 100 million years.
4
Extinction Nb 3: The Great Dying
252 million years ago, volcanoes in Siberia erupted for thousands of centuries.
Nine of every ten kinds of sea animal disappeared. This is the worst thing that ever happened to life.
Trilobites had crawled the seas for 270 million years. Here, they stop.
5
What emerged: One Animal, Everywhere
The world afterwards was almost empty.
In some rocks from that time, nine out of ten land-animal fossils are the same creature: Lystrosaurus, a pig-sized plant-eater with a beak and two small tusks.
A whole planet, and hardly anyone else.
6
The First Dinosaurs Were Small
231 million years ago, in the recovering world, the first dinosaurs appeared.
Eoraptor was about a metre long and light enough to lift.
For 30 million years dinosaurs stayed rare. The land belonged to giant cousins of crocodiles.
7
Extinction nb 4: The Night Pangaea Cracked
201 million years ago the giant continent began to tear open. Lava flooded an area bigger than all of Europe.
Three of every four kinds of animal died, including the great crocodile-cousins.
The dinosaurs walked into the empty world and stayed.
8
Then They Got Huge
With the world to themselves, dinosaurs grew enormous.
Brachiosaurus carried its head about 13 metres up. It could have looked in through a fourth-floor window.
It spent nearly all day eating, and never chewed a single bite.
9
Extinction Nb 5: The Asteroid
66 million years ago a rock 12 kilometres wide fell out of the sky and struck the sea near Mexico.
It punched a hole in the Earth 180 kilometres across.
By evening the sky was dark. Three of every four kinds of living thing were gone.
10
What Survived: Small Mamals
On land, almost nothing heavier than a large dog survived.
The winners were the diggers, the swimmers in mud and the eaters of seeds and dead leaves: turtles, crocodiles, small furry mammals — and a few birds.
Being small and hidden was everything.
11
Today: Look Out the Window
Those few surviving birds became about 11,000 kinds. A sparrow is a dinosaur, still here.
Five times life was nearly erased. Five times it came back, slowly, and prospered.
The next chapter is ours to look after.
12The End
