Why did dinosaurs go extinct?
Short answer: about 66 million years ago a huge asteroid hit Earth. Dust went up and hid the Sun. Plants stopped growing. Big plant-eaters had nothing to eat. Then the hunters had nothing to eat either. That is how T. rex and Triceratops ended. Small animals made it — including the ancestors of today’s birds. Birds are dinosaurs too. Just the feathered kind.
Where it hit, and how big it was
The place is called Chicxulub. That is the Yucatán Peninsula in Mexico. The crater is almost two hundred kilometres. It sits under the ground and the sea. You cannot see a hole from the beach.
The rock itself was more than ten kilometres across. Our Diplodocus card is 27 metres — three school buses. The asteroid was longer than a whole city. Scientists can still see the hit: a thin layer of clay all around the planet, full of a metal that is rare in Earth’s crust and common in asteroids. The same layer is inside the crater.
It got cold because lunch broke
The smash killed whoever was nearby. Then it got worse. Dust and soot hid the light for a long time. No light — no plants, no sea algae, no food for anyone. First the leaf-eaters go hungry — Triceratops and other giants. Then the ones who eat them go hungry — T. rex.
This is not a story about “it got a bit chilly.” It is a chain. No sun, no dinner. A huge animal needs a huge dinner every day. A small one needs less. It can hide. It can live on seeds or bugs for a while.
Who was actually alive at the end
T. rex on our site is 12 metres and about 8 tonnes, late Cretaceous, 68–66 million years ago. Triceratops — same years, nine metres. They were there for the hit. Brachiosaurus and Stegosaurus were not. They are Jurassic. Their time ended tens of millions of years earlier.
When people ask “why did the dinosaurs die,” they usually mean those last giants. The asteroid answer is about them. Jurassic animals are a different story: species changed before, without one giant rock.
Why a sparrow is here and T. rex is not
Birds come from small feathered hunting dinosaurs. After the hit, every dinosaur died except the bird line. Not “every reptile on Earth”: crocodiles and turtles made it too.
Why birds? Scientists are still piecing that together. Size, mixed food, and being able to fly away from a burned place show up a lot. None of that helped a giant T. rex. More in the guide “Are birds dinosaurs?”
Volcanoes were going too
In India, huge lava flows were spilling out in those same ages. The air changed from that too. But one dust layer wraps the whole Earth, and it matches the hit — not every eruption.
Short version: volcanoes happened, the hit happened. Without the asteroid you cannot explain that sharp line in the clay.
Questions kids ask
- Why did dinosaurs go extinct?
- About 66 million years ago an asteroid hit. Dust hid the Sun, plants stopped, big dinosaurs ran out of food. Birds — their small relatives — stayed.
- Where did the asteroid hit?
- Chicxulub, on the Yucatán Peninsula in Mexico. The crater is almost 200 kilometres. It is under the ground and the water now.
- Did all dinosaurs die?
- All the big land ones — yes. Birds did not. They are dinosaurs that walked through the disaster and live now.
- Did volcanoes kill the dinosaurs?
- Volcanoes in India really were erupting. Most scientists still say the asteroid came first: the same layer sits all around the planet.
- Did T. rex and Stegosaurus die on the same day?
- No. Stegosaurus lived in the Jurassic, tens of millions of years earlier. T. rex and Triceratops were there at the end of the Cretaceous.
- Can dinosaurs come back?
- The big non-bird ones — no. Their time is over. Birds are already here. You cannot clone a T. rex from a mosquito in amber. That will be its own guide.
Remember this
- If you draw the day the rock fell, draw dust and empty trees — not only a boom.
- Jurassic Park and the Cretaceous are different times. Stegosaurus next to T. rex is a movie, not a bone.
- The sparrow on the windowsill is closer to dinosaurs than a crocodile is. That is family, not a joke.