Dinosaur Extinction: K-T Event Questions Remain

During their 150 million years on the planet, dinosaurs evolved so many protective features, ranging from spiked tail clubs to helmet-like crests, that they seemed indestructible. Just 10 million years before the non-avian dinosaurs died out, dino populations as a whole were still thriving, with more different species than ever before colonizing the continents. But the Cretaceous-Tertiary extinction event, also known as the K-T extinction, put an end to the dinosaur era. It’s still a great mystery why such an apparently abrupt mass extinction occurred 65 million years ago, but a number of theories have been proposed.

Deadly Germs and Self-Destruction

Could dinosaurs have eaten each other to death? Experts in the past speculated that carnivores consumed so many herbivores that the latter went extinct, leading to the death of the meat eaters. Other scientists wondered if defective hormones and other degeneration weakened dinosaur populations. Yet another theory is that poisonous plants, or a deadly pandemic, caused great die-offs. Few of these hypotheses have been supported in recent years, however.

Volcanism

Volcanic activity remains a debated theory. It is known that at the end of the Cretaceous period multiple volcanoes erupted, particularly at what is now central India. These led to fiery lava flows that spewed noxious acid and carbon dioxide into the air. But would this air change have been enough to kill all the world’s dinosaurs? Although still unproven, it’s possible that a domino effect, leading to temperature increases, ozone layer reduction and lethal radiation, could have sent dinosaur populations into a nosedive over a relatively short period of time.

Asteroid Collision

One of the most widely researched theories holds that a large asteroid could have slammed into Earth. If big enough, such an asteroid could form a huge crater, sending dust and water into the atmosphere. If this didn’t choke out the dinosaurs, the resulting possible climate change could have done the dirty deed. Freezing cold weather would have followed such a crash, due to dust and moisture-forming clouds that would’ve been carried by strong winds. If this again didn’t kill the dinosaurs outright, it could have wiped out vegetation, starving plant-eating dinosaurs, a food source for carnivorous dinosaurs.

Some research teams believe they have found evidence of such a destructive asteroid. A crater about 186 miles across was unearthed in Mexico. Fossils and damaged sand grains in North America may also suggest that flowering plants disappeared relatively quickly at the end of the Cretaceous. A rare, meteorite-associated element known as iridium additionally might have made an earthly impact, since a thin deposit of it was discovered in 1979. While other theories for the K-T event abound, such as deadly radiation emitted from an exploding star or a sudden reversal of Earth’s magnetic field, the asteroid collision theory appears to be the most widely accepted explanation for the non-avian dinosaur demise.

Dinosaurs in our Midst

There is little doubt that non-avian dinosaurs disappeared as the Cretaceous came to a close. But little winged, feathered "dinosaurs," that is to say theropods, may still be with us. Most paleontologists now believe that birds evolved from certain dinosaurs. If so, the over 10,000 species of birds could serve as living proof that the dinosaurs were, and may continue to be, the most successful creatures ever to inhabit the Earth.