Cretaceous Paleogene boundary: Why we can drive today and why the dinosaurs died 66 million years ago!

Warning: this is not a one-line Q&A. It’s a ride, and only true readers should proceed.

What can be the reason we are able to drive a car or ride a bike now, that also caused our dino-friends to perish some 66 million years ago? The answer is… No, it’s not Cretaceous–Paleogene boundary, but its related to it –

Iridium

Iridium is the element whose alloy is used to make the spark plugs (igniter electrodes to be more specific) used in the engine of your cars and bikes. It is what ignites the fuel mixture inside the combustion cylinders. Capable of withstanding more than 45000 volts and temperatures higher than 2000°C (3632°F) while still maintaining its corrosion resistance and hardness, it is one of the only elements that can be actually used in a spark plug. But what it has to do with the death of the dinosaurs? 

Well, the answer is, the presence of more iridium on the earth’s crust than it should be (about 23,888,000,000,000,000 kg to 1,791,600,000,000,000 Kg). Most of the earth’s own iridium, along with other heavy elements sank to its inner core while the earth was still being formed. When it cooled, the earth’s crust didn’t have much of any heavy elements. How do we know that? 

That’s where Cretaceous–Paleogene boundary comes. One can tell the composition of the earth’s crust by digging up layers of soil and rock. The Cretaceous–Paleogene layer corresponds to the time when our earth was 66 million years younger than now. It tells us that up until then, the earth was not rich in iridium. Suddenly, someone or something added a whole lot of iridium all over the earth and it never happened again. So who was this unknown guest? 

The Answer is…….. Either an asteroid (The Alvarez hypothesis) or a comet. The debate is still going on based on actually how much extra iridium there is! Comets have less iridium than asteroids and a 2013 research (by Prof Jason Moore and Prof Mukul Sharma, Dartmouth College, New Hampshire) favours the comet. Nonetheless, they both are celestial wanderers who carry with them, amounts of iridium, that matches the extra iridium as indicated by the Cretaceous–Paleogene boundary layer. 

Asteroid

Comet

Now, can you see how all the blocks of jigsaw puzzle falls into place? It took not more than a year to unravel the true story. As it goes, some 66 million years ago, an expected guest, descended from the space, over what’s now the Yucatán Peninsula, Mexico, and bumped into the earth with all its might (impact energy in order of 10^8 megatons of TNT). The cataclysmic event unleashed an unprecedented destruction and a chain of reactions which lead to tremendous global warming and acid rain which covered the earth in clouds of dust and stopped photosynthesis for years ultimately, killing the big guys – the dinosaurs (called Cretaceous–Paleogene extinction). And oh yes, I forgot, it also showered a whole lot of Iridium all over the earth’s crust.
So the next time you turn the engines on, think about the poor dinosaurs who literally got dragged to hell, by the very element, that makes the starting of engines, possible in the first place !