Saturday, 11 August 2012

How do you set the entire earth on fire?

The Cretaceous–Paleogene extinction event was a large scale mass extinction of animal and plant species, most notably the dinosaurs in geologically speaking a short period of time. The primary cause of extinction was an asteroid impact so large that it severely disrupted the earth's biosphere. Such an impact would create a dust cloud big enough to block out sunlight for a number of years, fill the stratosphere with sulphuric acid aerosols and during the hours immediately after the impact everything that can burn will. 

Think about that, everything that can burn will. How?

Firstly it's important to understand that the asteroid in question was about 10miles in diameter, so big that when the bottom hit the ground the top hadn't yet entered the bulk of the atmosphere. Picture that, the bottom of the asteroid is touching the ground and the top is up around 30,000ft with commercial airliners. It really would be something amazing to see although I'd prefer not to considering it would mean I was seconds from death. 

Now that we know the size of the asteroid we can begin to work out what's going to happen once it hits the ground. 

Sound travels through granite at about 5,950m/s which is a lot slower than the speed of an incoming asteroid travelling at about 27,000m/s. This means that when the asteroid hits, the back of the asteroid will hit the ground before the shock wave can get to it. It'll smash all the way into the earth's surface. This means nearly all of the energy created by the impact is added to matter beneath the ground surface, for the asteroid in question that's about 1x10^25 joules. That's enough energy to melt about 100 times the asteroid's own mass or 5x10^18kg of rock, a small amount of that rock will vaporize instantly and travel about 60miles into the air, maybe higher.

Now you've got trillions of tons of lava raining down on everything from a height of 60miles. The earth has roughly 6x10^14kg of carbon in it's biomass which will burn in a matter of hours.

Everything that can burn will. 

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