Pretty much everyone knows that a giant asteroid led to the demise of dinosaurs on Earth – as well as a bunch of other species of plants and animals, as well.
You might not know the whole story, though, so let’s get into it.
In 1978, geophysicist Glen Penfield was studying a magnetic survey map of the Gulf of Mexico for his employer, Mexican oil company Pemex. That was when he first spotted a semi-circle he believed was the result of an impact crater.
Another employee at the same company had seen the same thing while studying gravity maps of the area.
Gravity differs across the planet due to the non-uniformity of Earth’s surface, both above and below the ocean. That said, there are still things that are considered to be anomalies based on what we expect to find at a certain point on the globe.
The anomaly found in the Gulf of Mexico was a pretty big one – big enough to have resulted from an impact that took out the dinosaurs.
The first paper to suggest an asteroid impact was to blame was published in 1980, and argued that the rare element iridium increases up to 160 times in samples taken from rock formed around that time.
“Impact of a large earth-cross asteroid would inject about 60 times the object’s mass into the atmosphere as pulverized rock; a fraction of this dust would stay in the stratosphere for several years and be distributed worldwide. The resulting darkness would suppress photosynthesis, and the expected biological consequences match quite closely the extinctions observed in the paleontological record.”
That said, it would be another decade before samples from the actual impact crater – dubbed the Chicxulub crater – were actually studied by Penfield or anyone else.
What they found was an unusually large amount of shocked quartz, as well as impact melt spherules.
The site was confirmed as an impact event, and the date of the impact lined up neatly with when we believed the dinosaurs to have gone extinct.
NASA explains in detail how these events matched up.
“About 65 million years ago at the boundary between the Cretaceous (the last geological period of the Mesozoic) and the Tertiary eras, a large asteroid came rushing out of space at a velocity of more than 25 km per second [56,000 miles per hour] and impacted the Earth at the tip of the Yucatan platform.”
The asteroid impact would have resulted in energy equivalent to 10,000 times the energy of a nuclear weapon, tossing up unprecedented amounts of dust and debris in the process.
“It vaporized, melted and shattered ocean water and the Yucatan target rocks composed of carbonate and sulphate. As a result, a crater some 124 miles in diameter formed.”
Volcanism could have also played a part in the extinction event, but the asteroid impact has long been favored by scientists as the main cause. The resulting changes to Earth’s climate contributed significantly to the mass extinction as well.
Bad luck, to be sure.
And a reminder that you really never know what the next (ten million) years will bring.
If you thought that was interesting, you might like to read a story that reveals Earth’s priciest precious metal isn’t gold or platinum and costs over $10,000 an ounce!