Dinosaurs lived on earth for millions and millions of years. Then almost all of them vanished completely.
What happened? Why did they die? No one really knows for sure.
Scientists call an explanation that has been well tested a theory. There are a few theories that explain why dinosaurs are no longer on earth.
For many years, most paleontologists thought the dinosaurs disappeared very slowly. They thought they died out because of climate changes.
Climate is the usual weather of a place.
Paleontologists who accept this theory think that the earth’s climate began to change at the end of the Age of Reptiles. As the climate changed, the world of the dinosaurs changed, too.
Paleontologists who agree with the changing climate theory say that many dinosaurs couldn’t adapt to the changes.
They think that over the years, more and more dinosaurs died, until there were none left. They had become extinct.
Extinct means “no longer living on earth.”
The changing climate theory was popular for a long time. But many paleontologists now have another theory. They think the dinosaurs were wiped out much faster. Their theory is called the asteroid theory.
An asteroid is a rock from outer space. Paleontologists who support the asteroid theory say a big asteroid hit the earth at the end of the Age of Reptiles. They think the asteroid was over five miles wide.
Wow! That’s as big as a whole town.
An asteroid that size would kill all the animals within hundreds of miles of where it landed. When it hit the earth, it would send a giant cloud of dust and smoke and ash flying into the air.
The cloud would stay in the air for years. It would block out most of the sunlight.
Without sunlight, the earth would get colder. Plants would die. Some dinosaurs would freeze to death. Others would starve. Soon they would all be gone.
For many years, paleontologists who accepted the asteroid theory wondered where the giant asteroid might have hit the earth.
Now they think they have found the spot.
Scientists have discovered a crater in the Gulf of Mexico. The crater is 120 miles wide. It is buried half a mile deep in the earth under the ocean.
A crater is a dent in the earth.
The crater is full of the same kinds of minerals that have been found where smaller asteroids have landed.
Today, most paleontologists agree with the asteroid theory. But it still has not been proven completely.
We may never know for sure why so many dinosaurs vanished from the earth. The death of these strange and wonderful creatures is one of the biggest mysteries of all time.
Turn the page for more dinosaur mysteries.
Paleontologists have been studying dinosaur fossils for almost 200 years. But there are some things they still wonder about.…
What color were dinosaurs? Were they brown and gray? Or were they bright red? Green? Yellow? Were they spotted? Did they have stripes?
Most fossils can’t answer these questions. But many paleontologists think dinosaurs might have been as colorful as today’s lizards and snakes.
How many years did a dinosaur live? Ten years? Thirty years? No one knows for certain. Many paleontologists think some dinosaurs lived to be over a hundred years old!
What kinds of sounds did dinosaurs make? Did they roar like lions? Did they honk like geese? Hiss? Chirp? Growl?
Paleontologists can only guess, based on the shapes of dinosaurs’ heads and bodies. Some dinosaurs had bony tubes on their skulls. Paleontologists think they might have tooted their tubes like bugles!
