Tony Crum, age 9, of Indianapolis, Indiana, for his question:

Why did all the dinosaurs die?

The dinosaurs departed 60 million years ago. This was ages before the human family came to live in the world. So there was nobody around to notice what happened to all those giant reptiles. We find only their fossil bones, a few fossil dinosaur eggs and some dinosaur footprints left in soft mud that later became hard rock. This is not enough evidence to explain the mystery of why they departed. But the experts can make a few guesses.

Some suggest that the big reptiles were used to the nice warm weather that had lasted for millions of years. Then the climate changed and the weather was too much for them. Others suggested that they lost their usual foods and starved to death. The grasses arrived at about that time and no doubt they choked out many leafy plants. The plant eating dinosaurs did not have the right teeth for chewing grasses. When they died from hunger, there was no meat left for the meat eating dinosaurs. But nobody knows for sure why all the mighty dinosaurs died when they did.

One theory is that the earth experienced a tremendous meteor impact.  This produced a huge cloud of dust that surrounded the earth for many years.  With limited sunlight many plants died.  Plants made up the main diet for dinosaurs.  When plants disappeared the big plant eating dinosaours soon became extinct.