Nobody knows what killed the dinosaurs
Not wrong, but our understanding became significantly more precise.
TaughtScientists have many competing theories about the dinosaur extinction: climate change, disease, volcanoes, mammals eating the eggs, or possibly an asteroid.
NowAn asteroid roughly 10 km across struck what is now the Yucatán Peninsula about 66 million years ago. The Chicxulub crater was confirmed in 1991 and the impact is the accepted primary cause.
What actually happened
Luis and Walter Alvarez proposed the impact hypothesis in 1980 after finding a worldwide layer of iridium, an element rare in Earth's crust but common in asteroids, at exactly the boundary. It was treated as a fringe idea for a decade, partly because there was no crater.
The crater turned up in 1991, in geophysical survey data that a Mexican oil company had collected in the 1970s and set aside: a buried 180-km structure centered near the town of Chicxulub, dated to precisely the right moment. A 2010 review panel of 41 scientists across disciplines endorsed the impact as the cause, and drilling into the crater's peak ring in 2016 confirmed the mechanics. Honest nuance: the Deccan Traps volcanic eruptions were happening around the same time and likely stressed ecosystems beforehand, and the exact weighting of the two is still discussed. But if your textbook presented a menu of equally plausible theories, that menu is closed.
Newsletter
Get new weekly revisions
Sources
Who was taught this
Still standard through 1996, so anyone who finished school between 1950 and 1991 learned the earlier version.