K-T extinction
AROUND 66 MILLION YEARS AGO
Species made e xtin ct 7 5 %
The most famous of all five mass extinction events is the Cretaceous-tertiary extinction – known better as the day the dinosaurs died. Geologists refer to the event as the ‘K-T extinction’ because the letter ‘C’ is shorthand for a previous geological period called the Cambrian. Crash-landing into what is today Yucatán, Mexico, an asteroid over eight miles wide plunged into Earth at around 45,000 miles per hour. This punched a hole 110 miles wide and 12 miles deep, called the Chicxulub crater. The impact would have scorched all the land around it within 900 miles, and ended the 180-million-year reign of the dinosaurs on Earth. What followed the impact was months of blackened skies caused by debris and dust being hurled into the atmosphere. This prevented plants from absorbing sunlight, they died out en masse and broke down the dinosaurs’ food chains. It also caused global temperatures to plummet, plunging the world into an extended cold winter. It’s estimated that it would have only taken months after the impact for most of the extinctions on Earth to occur. However, many species that could fly, burrow or dive to the depths of the oceans survived. For example, the only true descendants of the dinosaurs are modernday birds – more than 10,000 species are thought to have descended from impact survivors.