Most dinosaurs were wiped out by a sudden mass extinction about 66 million years ago, most likely triggered by a giant asteroid impact, amplified by massive volcanic eruptions and climate change. A small group of feathered dinosaurs survived and evolved into the birds that exist today.

The big extinction event

Scientists see a sharp break in the fossil record at the Cretaceousā€“Paleogene (Kā€“Pg) boundary, where nonā€‘bird dinosaurs disappear around 66 million years ago. This marks a global extinction that also wiped out many marine reptiles, flying reptiles, and countless ocean species.

  • Rock layers from this time show a thin band rich in iridium, a metal rare on Earthā€™s surface but common in space rocks.
  • Above this band, dinosaur fossils vanish, showing they did not gradually fade out after this layer formed.

Asteroid impact: main culprit

The leading explanation is a huge asteroid (about 10 km wide) that slammed into what is now the YucatƔn Peninsula in Mexico.

  • A roughly 150 km wide impact crater called Chicxulub matches the timing of the extinction and the global iridium layer.
  • The impact would have caused firestorms, megaā€‘tsunamis, and a dust and aerosol cloud that blocked sunlight, collapsing food chains on land and in the oceans.

Volcanoes and climate oneā€‘two punch

At roughly the same time, enormous volcanic eruptions in India (the Deccan Traps) were spewing lava and gases for hundreds of thousands of years.

  • These eruptions likely pumped carbon dioxide and sulfur into the atmosphere, driving longā€‘term warming, acid rain, and ocean stress.
  • Many researchers now think ecosystems were already weakened by volcanism and climate shifts, so the asteroid impact acted as a final, devastating blow.

Did dinosaurs already struggle?

Fossil studies suggest some dinosaur groups were declining in diversity before the final extinction.

  • Changes in climate and sea level may have altered habitats and reduced the number of species in certain lineages.
  • However, dinosaurs were still widespread and ecologically successful until the sudden crash at the Kā€“Pg boundary.

What about ā€œsurvivingā€ dinosaurs?

Not all dinosaurs vanished: birdā€‘like, feathered dinosaurs on the evolutionary line to modern birds made it through.

  • These smaller, often flying or gliding animals may have coped better with food shortages and harsh postā€‘impact conditions.
  • In modern classification, birds are considered living dinosaurs, so in that sense dinosaurs are still with us, just in a very different form.

Information gathered from public forums or data available on the internet and portrayed here.