Question: How did dinosaurs become extinct?

Anthony Redmond answered on 31 Jan 2019: last edited 1 Feb 2019 10:23 am

First off, some dinosaurs survived! And today’s birds are their descendants!

The dinosaurs as we often think of them however, died off as part of the Cretaceous-Paleogene (K-Pg) mass extinction event.

The K-Pg boundary, which is a thin layer of sediment in the geological record, is highly enriched with iridium, which is a common metal in asteroids but rare on earth, suggesting that the mass extinction event was probably caused by the impact of a large asteroid or comet around 65 million years ago.

A large asteroid impact would have released a massive amount of dust and ash into the atmosphere, decreasing global temperature substantially, and stopping photosynthesis by blocking the suns rays. This would have caused most plants to die, as well as many animals that feed on them. Omnivores and carrion eaters and insectivores would have been most capable of surviving in such an environment compared to pure herbivores or carnivores.

It mightn’t come as a surprise to you then that many other species than dinosaurs were hit by this event too (maybe up to 75% of all known species from the time went extinct!), generally only small species of mammals survived off things like snails and worms, which themselves ate dead animal and plant matter. Some cold-blooded species, even slightly larger ones (e.g. crocodiles) would have been capable of surviving too, because they were scavengers that only needed to eat once every few months. Not only species on land were hit, many marine species died out too, including sharks and fish, but an example that you probably already associate with this extinction is ammonites!

There are some other hypotheses for how the event could have happened, such as volcanic eruptions, or climate changes, but the evidence seems to best support a link to an asteroid impact!